Hi Brad, Alan Here. I have a repair business in New Zealand (Anvil Amplifiers). CEdist have done the same to me with a quad of 6550EH. Because the Tubes were in my stock for more than 90 days until used and I only then discovered that one of the tubes had an open circuit heater they told me I could not get a replacement. Am I supposed to test all tubes on delivery? BTW I now buy most of my tubes bulk from JJ direct or other brands from UK distributors. Just bought another 3000 Euro worth.

@TheGuitologist

2 жыл бұрын

It’s bullshit, ain’t it!

@neutrodyne

2 жыл бұрын

I'm in the US and have had the same proble with CE and their 90 day policy. I have tried to tell then as a repair center that I stock up on tubes and then sell them as needed. Some times the tubes set on the self more than 90 days before they are needed. CE told me 90 days was thier policy. I told them it was a unreasonable policy for a dealer/ repair center.

@highpath4776

2 жыл бұрын

UK has just done a free trade deal with NZ, so that should make you happy in the future - be good !

If there is high frequency oscillation in the amp going on as seen in the flashback and while you were testing it on the bench there is something wrong! If the customer doesn't use the FX-Loop disconnect it and put the amp back to original. If he want to keep it test it as well and ask how he is using it. Depending on what is connected there it also could lead to oscillation. High frequency oscillation can kill the amp without you even noticing it. Replace those sockets! And CHECK the coupling capacitors!!! If they are leaky the Bias will run away. Replace them with good 630V types as 400 are not enough! Yeah modern foil caps blablabla, i've had exactly that in a Laney. The cap was damaged internally and when it got hot it leaked and the tubes blew. Also by changing the grid resistors you have now changed the bass response of the amp. If the customer doesn't notice it okay otherwise enlarge the coupling caps. Keep an eye on crossover distortion when running it with less bias. Finally get rid of those 6550 and put EL34s in. Those are what the amp was made for. You are putting a V8 in a Mini and wonder why the brakes are failing.

Ya know, I have always pretty much considered myself a Guitologist fan and have always enjoyed the videos but this one disappointed me. Why would you expect a company to replace something that far beyond their return policy. There has to be a limit. Just because there has been a pandemic and the customer hasn't played any shows doesn't mean he hasn't used the amp. I haven't played any shows either but I still crank up at home. I could understand if it was a only couple months over the return period but how long was this... well over a year? The part that really disappointed me was that after you belittle and berate this employ on the phone and claim that the amp is not at fault, you proceed to test the amp again and discover that the amp probably was at fault. To me, it was you that missed the heat issue on the previous repair and had already been comped one tube. It seems that this company had already gone above and beyond their responsibility to you as a customer and I applaud them for standing up to you when you tried to bully them with threats of using your subscriber base against them. Just my opinion...

@petemoore8923

2 жыл бұрын

Well said sir!

@j_freed

2 жыл бұрын

Yes, given the global crisis (which nobody in the situation caused) Guitologist is placing the entire locus of control for the warranty runout problem entirely on the tube reseller. This would in principle also make the company liable for countless thousands of other products that have all been sold since December of 2019, regardless how the items were used or handled or stored for all that time. I think one assessment is to say: as with other crises like terrible wars, everyone owns some material loss from the pandemic, and we can’t all shift it onto someone else. It really sucks but in the balance we still have a really great life here to be grateful for. In fact, Guitologist might have done better in the long run sticking by this company… I don’t know. They did try to offer him the item at cost before he shut them down with the ‘long term customer’ refrain. That would be effectively one tube at a full loss, and one tube for zero gain, all assuming he’s 100% correct and above board. You can’t buy that good faith and respect. I guess businesses sometimes have to let customers go.

@verifiedhandle9103

2 жыл бұрын

@@j_freed lol except for the rich who have all gained wealth

@benlogan430

2 жыл бұрын

Even in amp and guitar land the talk of “sheep and goats” comes out. This is amp and guitar land. Rock and Roll.

@NewHopeAudio

2 жыл бұрын

100% agree ...this is disgusting.

I like ya Brad, but throwing your channel around like that is an ugly look. We all have problems bro, but come on.

@RobFeldkamp

2 жыл бұрын

Agreed

@paullee3660

2 жыл бұрын

That was a real Karen move. 2 in a row from the same amp, 2 years later. They are a business, not a charity. That was a real tantrum and he needs to grow up.

@j_freed

2 жыл бұрын

KZreadrs primarily post videos to make money on views… Think about it.

@TheEchelon

2 жыл бұрын

@@j_freed This one seems genuine though. It's really not that deep.

I never get tired of your intro graphics. They really take me back to the great days of cable. Keep up the good work

To be fair, it’s not that clear the tubes were entirely at fault, especially since the grid resistors were out of spec, which you replaced. As such, you should pass the cost on to the client and explain the tube failed and too much time has passed to qualify for a warranty claim. I can see their perspective as well, where do they draw the line?

@stephc4427

2 жыл бұрын

Wait a minute. The customer is responsible for his own equipment and the costs therein. Brad you are totally wrong to say that you have to eat the cost of the tube. That's you customer's responsilbity just as it would be if he had purchased a quad on his own and installed them. You need to get your business acumen in order. The supplier already did what they agreed to with the initial replacement. Plus, you have NOT proven that the amp itself is blowing up tubes nor did you explain that the bad tube was in the same socket as the other that faile! Cmon, get real,

@tombryan1

2 жыл бұрын

@@stephc4427 It's not the customer's fault. The expert who repairs the amp has possession and agreed to repair it. Good business practice means taking responsibility. You wont last long in business if everytime you misdiagnose you throw it back into the customer's lap.

@Hahnsoulo

Жыл бұрын

@@tombryan1 That might be true in the world of guitar amps, but not in the world of cars. Plenty of mechanics will replace a part because 90% of the time that's the part that needs to be replaced when symptoms X, Y, and Z occur on a particular model of vehicle, and then when it turns out this particular case is one of the other 10% they have to replace something else to actually fix the problem, and the customer gets charged for the part and labor of both parts. Have you never heard of someone having to take their car back to the same shop 2 or 3 times before it actually gets fixed? It's pretty much standard practice to fleece customers whenever possible, and these shops don't go out of business.

@erichkaanikin3555

7 ай бұрын

You also don’t vacuum the dust off. Isn’t that proper amp hygiene?

@erichkaanikin3555

7 ай бұрын

Gosh, how can you possibly think you’re anything close to rational by claiming that a purchase with a 90 day warranty should still be honored three years out of warranty because the customer didn’t play, whether or not due to pandemic. That’s ridiculous! And certainly not relevant to the vendor’s warranty. Your reasoning is pathetic and an embarrassment to the customer. Sad🙈

"I'm a Yelp reviewer and I'm very important...." All joking aside, I see both sides, but its just a shitty situation all around. Let's just blame the Russians.

@RaulHernandez-lg5nw

2 жыл бұрын

Anyone who See's both sides of an issue, See's nothing at all !!!!!

@TheRustedShackleford

2 жыл бұрын

@@RaulHernandez-lg5nw ummm... thats a pretty moronic saying

@taknmybeatings7036

2 жыл бұрын

@@RaulHernandez-lg5nw that is tied for first place of the all time stupidest thing that I've ever heard! But I can see why you would say it.

@taknmybeatings7036

2 жыл бұрын

@@RaulHernandez-lg5nw I was just lying! I have no idea why you would say such a moronic thing! ...and on a public forum no less.

There were a lot of things you could have done before berating CE Distributions customer service like that; they run a good business and probably won't feel your absence at all. See Pentode3000's comment below - he covers most of what you should have checked. You know, I read the title of this and thought "NICE, Brad probably dealt with a really perplexing issue - I bet I'm going to learn a lot from this"... and then you started making phone calls... Please just post a 30 minute video of you fixing an amp next time and keep the yelp reviews off camera. It's unbecoming. "I'vE GoT 125k SubZ on Yew TewB!" - Yeah, and we're all going to watch you totally play yourself.

This video is reminding me, of how long I have been working on tube amps, and also how long I have noticed subtle problems, that all contribute to catastrophic failures sometimes. Brad , I really appreciate Your channel and EXCELLENT videos. I will say I have commented several times on bias issues, and also parasitic high frequency oscillation. Although Marshalls have pretty good bias circuit components, I have noticed many times that they do not use the best pots. Often (35 years) I have ended up replacing them with fender style CTS pots, changing the typical reostat style circuit, to a voltage divider configuration, so the center sweeper goes to bias points through the splitting resistors, and eliminate the 2nd bias cap, as it causes the bias adjustment to take a minute to settle. A really solid bias setting,, that is a little cool makes for a long life with an amp used at high vol for hrs. Just as I was muttering to my self about hi freq or parasitic oscillation, I was much pleased, that You did show the earlier video excerpt of the parasitic osc problem showing up. If You use a 100 mhz or higher 'scope any parasitic oscillation problems will show up. That schmeary waveform is a lot of very short wavelengths of high frequency oscillation. If i ever get my amp You tube channel up, I will try to go through in detail, design issues that cause these problems and problems that show up as an amp gets older. Briefly an amp can become an oscillator very easily (at hi frequencies) if a couple of stray capacitances to ground in a series of gain stages show up in a negative feedback loop. You can't find THESE, misbehaving, until the tubes are in place and the amp is operating. Hi frequency oscillation can end up manifesting in a certain output tube, even when the tube is moved from one socket to the next, because each tube is slightly different, and at 50 Khz to perhaps several 100Khz, extremely small mechanical differences in the tubes can localize the power disipation of the oscillation in one tube , even though the overall instability of the circuit is to blame. It is very time consuming to go through amps to improve the stability. In this case it does seem that there was a bad run of Sovteks and especially problems with filaments overheating. I have had the same kinds of problems recently (over the past 10 years) with cathode filament shorts, with many different tube distributors, and manufacturers. I really like CE dist in general, but have had a couple of problems , with them and others more recently. It is actually very gratifying to realize that someone else shares my frustration, though it would be much better if we all could come up with a solution. Paul Carlson of Carlsons Lab YT does go into some issues of filament flash over during turn on,... that guy REALLY knows his theory ! A problem which can show up at a gig, that doesn't show up at Your repair facility are problems with Lamp dimmers making RFI, or outdoor concerts using power generators that supply squared off power waveforms. Brad I also really appreciate Your musicianship. Do You play out much? You are a great player!

"Kan I speak to your manager?" - Karen The Guitologist :D

I bet it's got something to do with electricity.

@swettyspaghtti

2 жыл бұрын

XD

@metalmig

2 жыл бұрын

🤣

@VashStarwind

2 жыл бұрын

lol

@rangerdoc1029

2 жыл бұрын

Nailed it

@docdeens4030

2 жыл бұрын

It could also be thirsty. Pour some water in it.

I hope CE Distribution discovers the error of their ways. Good luck brother, we support you.

The guy on the phone is like "we will survive".

Heck yea! What's better than a long form Guitologist amp repair mystery video on a lazy Saturday late afternoon? Thanks Brad!

@OG_Wakanobi

2 жыл бұрын

Viva Barnes on a Sunday evening?

The amp isn't built for that kind of power consumption. I think these tubes need to be biased to draw no more current at max volume than the original EL34s would. Anything higher would reduce the life of the output and power sections. Another thing I don't hear about much is octal socket contacts. I have encountered so many amps with socket problems that I check all the octal contacts of every amp with output tube issues. I use an old screw driver (with the tip rounded off) with a shaft that is only a hair's breadth smaller than a tube pin. Any contact that doesn't have a fairly firm grip is gently bent to make better contact. If the contacts are charred, the socket is replaced. Better safe than sorry.

@highpath4776

2 жыл бұрын

Good Analysis.

@acexxxoasis

2 жыл бұрын

Not gonna lie I'm not trying to stick anything metal into a tube pin socket, drained or not I would be shitting myself one way or another!

@golgothaassassin5035

Жыл бұрын

Agreed!!! I've seen so many of those cheap china sockets fail, or cheap wire that breaks down with use, or thin conductive boards.

Check the coupling cap from the previous stage feeding the grid. If leaky it will put a positive voltage on the grid. This will kill the tube.

Brad...great vid as usual. Always learn a ton watching you diagnose amps. Something I noticed, I don't believe I've ever seen you feature an original Silver Jube repair or mod on your channel. Would love to see you pull the guts apart on one of those bad boys.

I watched this all the way through and at the end the conclusion is that it's most likely that the amp is blowing the tubes, so there was probably nothing wrong with those Sovteks that failed? This makes a bit of a mockery of the first part of the video where you are ranting at the company that supplied the tubes. I agree a 90 days wholesale warranty is a bit farcical, but you really need to provide some balance here. Maybe you should have checked the readings on the tubes before you called the supplier?

I've also had problems with Sovteks. I recently returned a 5AR4 that arced over with very low hours on it. Also I've had problems with 6l6s. One low hour tube developed grid emission and the other one became noisy.

Was working sorry I missed this live but man you had me cracking up a couple of times

After CE hung up the phone, I'm sure they will have agreed that the win for them is, that they no longer have to deal with you.

Thanks Brad, I really enjoy your videos. I hope you stay active in this field of employment and sharing with all of us your repairs. I think I would remind him he needs to jam with it every day so that if it breaks again it will fit the parameters of the 90 day warranty with the company that sold him the tubes to start with. Good luck and God bless.

If that is an added effects loop then the return jack is the best spot to inject your generator as you'd be passing all the preamps and tone stages and end up with a much more linear sine wave for analysis aft the output. There would be no guessing where any issues with linearity are coming from.

Very interesting video as always. Thank you for making it. I know very little about amplifier repair, but I'm just curious if trying another brand of tubes to cross-compare results would be useful here.

Brilliant I wish I could be like Brad on the Phone!! Love you Brad! x

I changed 2 of my 6l6 ,s to el34,s in my mk4 boogie .these where genuine mesa tubes .stuck them in and one redplated .bought a pair of matched sovtec,s .perfect !!!!!

haha funny, i was just watching the older video on this amp to see your PPIMV wiring. and BOOM! here it is again

Hi Brad, great video. Old school 6550 amps used to be driven regularly well beyond their rated max screen voltage. New production 6550s are not at all happy with high screen voltages. I have a stereo amp that drove 6550s at 550v on the screen. Used to work fine with nos 6550s. Eats new production 6550s like candy. I switched over to kt88s and tube failure ceased. KT88s are rated for over 600v on the screens. 6550s are only rated for 425. Check the screen voltage. What are the screen resistors? You may want to increase these. I use 1.5k - 2.5k for Amps like this. Adds a hit of compression but most often the effect is a desirable one. Or increase the dropping resistor for the screen supply to lower it. Although you would then probably need to decrease the droppers for the preamp supplies to bring them back up a bit. New production 6550s are just not as rugged as the old school ones. Their design maximums can't be exceeded like the NOS tubes.

@TheGuitologist

2 жыл бұрын

1K screens

@colincampbell4505

2 жыл бұрын

@@TheGuitologist Under the circumstances you encountered, I would bump those up. 2k probably won't hurt anything but might help the 6550's last longer

This is what I love to see life in the real world take care as always your in them Dude!

Was this amplifier designed for the output tubes you are using? Do you have resistors from each cathode to ground to balance the load? Does each conle

Reminds me of the time I once bought a brand new Ampeg VL-503. Had problems of the sound intermittently dropping out. Changed out cables, guitars; all made no difference so it had to be specifically the amp itself. At practice, I'd be playing then there it goes! The guys would look over and say "What happened!" Tue store owner I bought it from obviously got tired of seeing me haul it back in. That ended a casual friendship and I had bought quite a bit from him over the years. When it worked properly, that Ampeg WAS a beast, and even though I pushed it, I never abused it.

How to turn your heavy metal 🤘 amp into a smooth jazz machine…. LOL 😂 Brad, my man, you was put between a rock in a hard place. Learned a lot, great video.

Hey Brad, I am an amateur radio operator. There has been issues for many years with power tubes for Amateur Radio power amplifiers, sometimes they were really good ones, and other times they would feel rather quickly. The quality with these things is all over the place

@n8sdr473

2 жыл бұрын

Absolutely same experience here as well TUBES these days are horrible, and most are just old stock and vacuum seal deteriorate over time

did you check resistor values of R35 and R36 when it's hot? looks like a bias issue from excessive heat at the sockets. also noticed a damaged resistor near the 10uF 160v cap...

I always cringe when people start dropping the Fbomb with customer service reps. They are trying to do there job. It’s yelling at a the guy who is just doing his job.

@TheGuitologist

2 жыл бұрын

There was no yelling. Standing up for oneself isn’t yelling. I’m not sure where this idea comes from that one isn’t allowed to express frustration in stark terms. It needs to change.

Do you think it would do any good to tell Sovtek about these defects? I thought 4-6550’s would easily handle 100 watts?

What does the SP12 or AP12 numbers mean on power tubes? I'm guessing they have tube testers that measure the transconductance of the tube and they MATCH the transconductance values

Does each control grid have a series resistor to prevent oscillation? Are the screen voltages higher than the plate voltages? If all of these things are as designed the tubes should last.

Hi. Im a fan of your channel. I have a question regarding powering up an amp slowly with a variac. Our mains voltage is around 230-240 ac volts. At what voltage should i start with the variac and how many voltage increments and time between increasing the voltage to the amp until im full 230 volts? Wil this also work with rack effect unit that hasnt been used in a long time? I was thinking of powering it up slowly to not blow and capacitors. Thanks.

Correct me if I'm wrong but a 50w 2204/1987 should be running a plate voltage of 390-ish and the 100w 2203/1959 around 450-470v on the plate, right?

How close matched should a set of tubes be?.Not a risk to replace non matched tube and hope it work together with its companion.?They work in pair yes?

The gifts that keep on giving. Soul bonded together..... forever.

So did changing the resistors to 82 lower the output wattage. Your tech said those amps are not happy with anything other than 82. If that thing was making too much power because of the 150's that could melt a good tube, right? And running them at higher than they are rated could find different weakest spots in the tube causing failures in more than just one way? I have a feeling it will be fine now.

Ah finally time to catch the amp repair video!

Can the cathode resistors not be replaced with 4K7 resistors rather than 1K0 resistors just wondering.

have you checked the o/p transformer resistances?

I had to watch this video again and I just realized that this amp has a circuit board and not a turret board. Marshall had a passel of trouble in the late 90's with conductive circuit boards used in the DSL and TSL models that would exhibit this type of failure as evidenced by slowly rising bias all the way positive many times. This is not saying that the board is the culprit but I had to have another look. I still don't know, it's a tricky diagnosis.

@SIXSTRING63

2 жыл бұрын

Yep, I have taken a Dremel and cut the PCB around the grid pin and ran a wire to the grid stopper resistor. This takes out the chance of a conductive PCB bleeding positive voltage from the screen pin next to it changing the bias voltage. I’ve done 12-15 TSL, and DSL amps with runaway bias. Seems his bias was changing as it warmed up. Marshall has been using these PCB’s since the late 70’s but whatever substrate they used in the 90’s was conductive with heat. You could take a heat gun with a meter clipped to the grid and see the resistance change as the heat increased on the PCB.

@omarcusihuaman4261

2 жыл бұрын

Hey, how can i contact you? Do you have an IG account?

@BustedJunkStudio

2 жыл бұрын

@@omarcusihuaman4261 Yeah, I do, it's bustedjunkstudio but I don't use it much.

I've got a tube amp..don't know alot about it ..I like it loud...but I was thinking about the electric where he's gigging..would he benefit from having a brown box to make sure his voltage is no higher than 120...if I'm wrong just tell me I don't know what I'm talking about ...lol...or is brown box for bias

Problem is Brad, if you bought 10,000 tubes, they would be talking to you. You only bought 4, so there isn't enough wiggle room to replace the tube. They replaced one, and you're asking for another. I side with your prospective, but I think you may have some success getting in touch with New Sensor.

@SimonLarkin-CSRecording

2 жыл бұрын

I think he's bought a lot more than 4. If you listen he has been a customer since 1994 and spent thousands of dollars.

@chrissullivan40

2 жыл бұрын

Brad buys lots of tubes

What was your ac measurement at speaker at full load test and how much was it drawing... Not at idle.. the amp was feeding back at one part in your vid.. have ohmed out the feedback circuit...and pot... Just wondering? And tube sockets!! I bang on them with drum stick! And I always put a tube in.. then go to bottom and make sure all pins feel seated. U be surprised how many get pushed down deep barley making connection with the pins.. and phenolic sockets get ! Hot !!! And crack = arc = more tubes! I think tube sockets is the problem.. but if amp is feeding back on itself.. that's another prob.. keep us informed. I'm curious...

Good evening, Brad et al. Stay free. All the best. Rab 🍻 😎 🌠

I have a Digitech 2112 that errors when i go through the presets. It reads not enough space on s-disc A1. Do you repair effects processors?

No matter what’s the fault the fact that you’re an exemplar customer should warrant better customer service.

My current tech refuses to use Sovtek tubes. Thinks they're junk OEM stuff that Marshall puts in their factory amps to save a buck. Sure enough, after a similar problem blowing one tube after another in my JTM, I went to a different tech and this guy switched to Tung Sols; it has been rock steady ever since.

I used to bias those old Unicord distributed Marshalls using the 6550 specs and some of those amps kept coming back. Mostly with tube related issues until someone scolded me for it. The PT is what can't handle the extra current draw when using the 35W plate dissipation figure. You almost have to ignore the 6550 specs and bias the amp like it was using EL34's. The amp would have had a 5A mains fuse if it were designed to run 6550's like the Marshall Major, which does have a massive PT and OT to boot. I noticed the PT getting super hot in the amps I was biasing using 35W max dissipation. Once I started backing off, the amps stopped coming back to the shop and had less tube failures as well. Hopefully this helps. I think that cold biased sound of those tubes is why people get it in their head that 6550's and KT88's sound a certain way, when in reality they're just cold biased and have a lot more perceived headroom as a result. Tubes are getting expensive and a lot of times I've just converted those amps back to EL34's by changing those 82K or 150K grid leak resistors to 220K and adjusting the bias range resistor if needed. It was a strange reason Unicord got Marshall to make that change to U.S. imported amps in the first place and I think they gave it up around 1984 or so. As always, your mileage may vary. You know what you're doing. I'm just sharing my experience with you in case it helps your issue. I enjoy your channel so keep up the good work and have a great day.

@TheGuitologist

2 жыл бұрын

I appreciate you sharing the benefit of your experience. Thanks for the comment. Loads of others in the comments also concur with you. I have learned a valuable lesson on this one. I'm not immune to learning.

@purgasound

2 жыл бұрын

@@TheGuitologist Thanks for the kind response. For the record, I don't believe that biasing in anyway had anything to do with those tube failures, especially the one that had the toasted white getter flash. I agree you got sent some bad tubes. I had three modern "Mullard" EL34's from a matched quad arc internally and blow in an amp that had no other faults. That was probably the most astounding set of failures in new production tubes I've seen.

A very interesting video! I hope the Sovtek people will see this.

MIght have been worth checking the amp out with EL34's (which is what it was built for) to see if they too ran too hot at high volume.

What Power Transformer number does it have? DE 4145?

Seems like something preceding the tubes is an issue, you gotta be missing something.. MrCarlsonslab channel might have some suggestions- dudes amazing with stuff like this.

Have not watched your videos for over a year because of your constant drama. I really find your videos INTERESTING. It looks like it's the same old thing.

When I saw you taking out the last tube from.the socket an hit the cabinet, I remembered once I pulled out an EL34 with the same system and the top of the bulb hit the tip of a screw inside and the tube broke.

Maybe you jumped the gun on blaming the tubes…. Awkward

Im so happy that i use the different tubes I use today in my amps. Right now I have one amp thats running their "stock" type of tubes. But that amp is only running the stock power tubes 6L6. I converted all my 12ax7 preamps in my amps to 6n2p. I have a switch to go between 12ax7 and 6n2p. These preamp tubes are between $2-3 per tube and they sound every bit as good as brand new 12ax7 JJ, i think they sound better. They are also NOS military spec. But you need to do research and find out if these will 100% work with your amp, do your home work. Now in EL84 type amps im using 6p14p power tubes, once again Military Spec NOS and these are about $3-4 per tube. They sound amazing and i didnt have to mod my amps. I did mod my Blues Jrs tho so i have not tried the 6p14p in a Blues Jr that still has its bias wicked hot. Those come with 22k resistor and it runs EL84 style tubes too hot. Need a 27k or 32k replacement resistor and it cools bias down. For my 6L6 based amps ive been using 6p3s which the new amps most of the time need their bias to be cooled for these tubes. These sound wonderful and are $5-7 per tube for once again a Military Spec NOS. Reason im mentioning all this to yall is because when i have problems with my amps, im able to have problems like this video has without the hassle of pricey tubes to replace. If i need to put new tubes in my amp its like $18-25 total to put new tubes in the entire amp. That leaves me more $ to fix other parts of the amp etc. Im not saying this is for everyone, but Ive been burned buying expensive tubes and trying to deal with tech support with some of these companies, i wont name anyone companies tho :-P . When your repairing either your amp or someone elses and the company that sells ya a crap tube gives you BS like this and in the end you end up having to pay for it. At that point why am i fixing this amp ? Seriously. Dealing with BS from companies and the pricing forced me to find another way to keep my personal amp collection running. Take advantage of all the information out there folks and look for ways to make your life easier. Sometimes they take a little more work, but in the end youll be in a better place to deal with anything that comes up. I read up and asked about the preamp tubes and learned what i needed to know, same with the other tube types i mention above. But ask people if you have other options, because most of the time you do. Ive converted my amps and i have converted a few amps for people i know, who now have spread the word themselves. I was shocked when recently i saw how much it costs to retube a blues jr with 3 12ax7 JJ and 2 EL84 JJ tubes... $125-150+ WOWZA!!! Its a Blues Jr !!! How much does it cost to put new JJ tubes in a Twin !!. Was a reminder that im happy ive learned so much about the amps i use and ive asked questions and done the homework, its paying off right now. Id spend well over $1500 easily to retube my amps with say 6L6, EL84, 12AX7 etc. Brad ive dealt with your pain with trying to return bad tubes, those places have ya by the balls. Its really at their discretion if they will help you at all. They sold you a "working tube" and they act like if there is an issue its your fault and you did and blah blah blah and they stop listening to you. The guy on the phone is this video honestly stopped really listening to you at all early on. I dont think he wanted to bother his manager and knew he could play the card he did. Im too old for this shit and i dont think anyone should have to deal with people like this. Shame a lot of places are a no go on ordering stuff from after experiences like this. Now when i find a place that does go out of their way, i make sure i mention that and write a review now. I loved owning vintage amps, but now id rather build my amps or choose amps that i feel more comfortable traveling with. When your traveling with 2 1968 Twin Reverbs all original, there is always some in that crowd whos thinking "Thats a nice amp!" and i dont mean they are saying that in a good way. Ive had stuff stolen and i know 100s of musicians over their time on the road who have had stuff stolen. Thats why I dont tour with my Gibson custom shop guitars anymore. But their are many reasons ive done what ive done but seeing this amp drive ya nuts brad and then to get on the phone... reminded me of my own experiences.

@ctcards2636

2 жыл бұрын

Man i just finished watching the video and hot damn, i had to smoke a cig and breathe lol. That brought me back to some dark places lol. Brad bless your soul for putting yourself out there to try helping the owner of this. Sadly im not surprised by this and it seems to have only gotten worse. The days of the customer being right is out the window. Like now in this world your guilty until proven innocent. Its crazy. No one ever wants to take responsibility for anything anymore. But hey there are good people such as yourself out there and others that keep the world truly going round. ;-) Thanks for the video as always.

@ctcards2636

2 жыл бұрын

You mention people not wanting to buy tube amps anymore. Well i agree and thats why i changed my live setup. I use to use Twin Reverbs on tour. Thats how many tubes and i always traveled with spares. Thats a lot of $ in tubes. Well recently about a year ago I bought a SMS Classic Tube Preamp. Its based on a Twin Reverb preamp and has 2 12ax7 tubes. Thats it 2 tubes. And i have that running into a ART SLA-1 SS power amp. I have this setup in a rack head case that looks like a amp head. This amp to me sounds better than my 68 Twins, call me crazy, but until you try one of these thru the right power amp you may not believe me. But there are a lot of guitar players using this SMS CTP right now, well known touring musicians. But my point is im moving away from tubes as far as i can, i still dont like straight SS amps. But i found this setup and im glad i did. I travel with roughly 36 less tubes. I can run 12ax7s or with an adaptor i can run 6n2p preamp tubes. Both tube types sound awesome. But the day is coming where tubes are gonna really start disappearing from guitar amps because no one wants the hassle of dealing with the price, shitty customer service when theres a problem and the reliability issues. Now a days your basically buying a tube with no warranty, because if you buy them as spares and you dont use them for years, even if they sit in the box and you never remove them, they are out of warranty in 90 days. I guess you can pay even more to have them test it, but i dont know if i trust some of these places actually doing anything extra like that. I feel like once these places have your money they are done helping you out. They will help you out and go that extra mile if it means putting money in their pocket. But god forbid theres an issue, and with tubes there is gonna be issues. Thats like a company who makes light bulbs telling customers theres no way the bulbs they ordered could possibly break or be defective in shipping. Shit happens we live in a world where stuff happens, you have to meet people half way with this shit and these companies dont want to do and the people they are hiring these days are obviously not getting trained well, so this goes up in the company to the managers that some how are managers now. Basically weve allowed lazy people to legitimize being lazy, its the new norm. Business 101 is the customer is always right. Also just as Brad says, if the tube company never hears about problems from these companies, how will the company continue to build good tubes ? They need the feedback to know they had a problem and fix it. These sellers dont understand that, they are young and no one taught them the fundamentals of how this shit works. Sorry rant over haha

Could you go on ebay and by a GE or Sylvania tube used ?

What is your source of schematics? I can never find schematics (or the correct ones) for guitar and bass amps.

@CyberChrist

2 жыл бұрын

Indeed...

I like your vids, I have a solid state amp, I dig your stuff. This might be stupid, but the resistor value was changed at some point, were they increased for more power? Could it be an improper master volume pot replaced as well? " this one goes to eleven" I'm an electrician , electronics are a different beast!

26:54 Brad's channeling his inner Karen...lol

@TheGuitologist

2 жыл бұрын

My inner Garen.

@FuquarProductions

2 жыл бұрын

@@TheGuitologist perfect!

@kristopher6031

2 жыл бұрын

@@TheGuitologist LMFAO

Aside from who or what is at fault, here in New Zealand we have a very good piece of law called the Consumer Guarantees Act (CGA). It basically states that all goods and products must be fit for purpose, of acceptable quality and last for 'a reasonable period of time'. The CGA works over and above any warranty by the retailer or manufacturer. Example - you buy a TV with a 12 month warranty. 18 months or two years later it develops a fault. The retailer has to repair, replace or refund because an item like a TV would be expected to last at least 5 years. Whether they repair, replace or refund is up to the retailer, unless: • the problem can't be fixed • the problem is of "substantial character", e.g. the item is unsafe • the retailer takes too long to act on your complaint. Then you get to choose what action you want. The act only applies to things bought for personal use, it doesn't apply to goods purchased for commercial use, trade purposes or where you are making an income from their use. I don't know what laws you have in the US, but would be interested to know if there's anything like the CGA.

Did you check BIAS stability ? Spring retainers are ground electrodes on top of the tube all around the anode, it can be dangerous. A current from plate can hit the glass over small spots , It depends on tube geometry. Usually no problems with el34, but other tubes may need different retainers..

Hi, maybe its all clear by now but your problem is high frequency oscillation because of the more than 50K return path to ground from the tube control grid. You can get away with more than 50K but with a very careful choosen maximun screen voltage and a super well designed output transformer and power supply. HF oscillation in 6550 occurs at high power usually and its very destructive for the internals of the tube. Marshalls are prone to it because of the long cabling in the power supply, in my opinion, and because OT are never well balanced, besides the obvious errors in the design. Thanks for the video.

@Dennis-mq6or

2 жыл бұрын

I thought that was what those grid stopper resistors were for. They usually eliminate any of those problems you described.

@alejandrosilva7520

2 жыл бұрын

@@Dennis-mq6or Indeed but the total value to ground, thats the stopper resistor plus the one that goes to the bias supply (ac ground), has a limit.

@TrakThora

2 жыл бұрын

You are right. I smell oscillation or alot of ripple.

I ordered some pricey Mullards F1 EL34 and pre tube's as well The power tube sounds so good I haven't even popped the 22ax7's in yet I use nos whenever I can I tell you my Marshall experience is that they seem to need service practically every year

I had a similar beef with a drum pad from Alesis. The pad broke within warranty, not because of miss use, the store sent it to the distributor, yes the distributor; the response from both was that they couldn’t replace the pad and it had to be repaired, and I would pay for the repair. I reluctantly agreed. The thing went to the distributor to be repaired and came back with a awful job with freackin cement glue showing. A BS repair job, that I simply could not accept, so I did not payed for it and they kept it. This is the best part; I contacted Alesis through their forum, explained them the situation and they promptly offered to send a new pad.

@TheEchelon

2 жыл бұрын

How's that similar? This was way out off warranty, they already replaced it once and it was probably the amp's fault...

@simaojoseph

2 жыл бұрын

@@TheEchelon look up "similar" in the dictionary.

I'm glad you changed those bias resistors. Note that the spec sheet at 59:23 shows the maximum grid resistance is supposed to be 0.050 Mohm. 68K is still too high, but 150K would be 3x the spec. It's unclear what happens if you exceed that spec. Some say you can have runaway bias - especially when the tube gets hot or gassy.

@decadantdog4444

2 жыл бұрын

That's what we have in politics right now, "runaway bias".

@TeleCustom72

2 жыл бұрын

Exactly this. I've had these amps back in the day where they still had 220k bias splitters with 6550s installed and the bias had run away and burnt up the valves (even with the bias supply adjusted to be biased correctly at idle). We get away with things in valve amps as they're very robust, but sometimes you get caught out. I too spotted the 50k max spec at grid 1 of 6550s. Some Marshalls in the mid 70s (with KT88s / 6550s) used 68k resistors for this application, so Marshall obviously were aware of this (despite still being over spec). I say that the bias will run away, but exceeding grid 1 spec might just (in some cases) cause the valve to become unstable and/or fail.

@glenwhatley8034

2 жыл бұрын

The way I understand it is the grid stopper resistors work with the tubes interelectrode capacitance to prevent oscillations in the tube. If the tubes were to go into oscillation for any reason they would inaudibly be drawing high current trying to amplify that ultrasonic frequency and all you might hear is a slight hissing. If the player were at a gig, he'd for sure never hear this or probably think it was just noise. I've see this type of oscillation in many older amps were it is merely lead dress causing the oscillation and sometimes a decoupling filter. The power tubes do their level best to honoraby amplify to the max whatever frequency it happens to be oscillation at.

@ethanspaulding6067

2 жыл бұрын

You are right Russell. Additionally, that spec is for a single tube. The leakage current from two tubes will generate 2x the voltage across it so 150k is 6x too high. As HTH AMPS says below, we do get away with a lot fo stuff in tube amps!

@russellhltn1396

2 жыл бұрын

@@glenwhatley8034 A valid issue, but I don't think that's what's happening here. A higher resistance value would lower the frequency of the resulting low-pass filter - reducing the problem, not creating one.

The fuzzy sinewave is a high frequency oscilation impossed over the signal. You cant hear it but it burns stuff. Uncle Doug once had that issue on video. I once had a damn relay with no visible carbon tracking, I did scrape it alot and still had the coil leaking current to the switch side. Could your socket become conductive internaly also? Thanks for the video Brad

@TheGuitologist

2 жыл бұрын

I think that issue was the output tube already being intermittent, or lead dress related.

@russellhltn1396

2 жыл бұрын

Sure looks like parasitic oscillation to me. The only way you're going to get that smear is if there's some high frequency stuff mixed in. (Or very low frequency) Since that looked like a preamp stage, I'm not sure as you can blame the output tube. Fixing it by moving a wire would be consistent with a parasitic problem.

@auntjenifer7774

2 жыл бұрын

@Orandy oh, you are one of THOSE guys 🤣🤷‍♀️🥂

@brucepickess8097

2 жыл бұрын

@@russellhltn1396 I agree with your comment on possible hf oscillation. If he'd changed the scope triggering and expanded the time base that may well have indicated that. Definately hf oscillation can cause problems. I've experienced similar problems in hifi amps and they become high power oscillators drawing excessive current.

Do you have the proper load on the output? Power tubes like the proper load.

So it wasn't the tubes and the whole seller CE, wasn't at fault? It's very confusing now!

You are not alone with this issue as far as the supply house, and other products. I've had the same thing with other stuff, and the same deaf ear. 🙃

Check negative bias before you put any tube in amp . Don't be amateur.

So it was not bad tubes? Do you need to make an amends to your dealer? CALL Marshall and go off on them.

What's the 4th 12AX7 for?

Was the quad set badly matched?

Is it possible to tame the power supply..? Seems like this one is stout and then some

Hey Brad keep an eye on Brimar, there are a group of people over here in England trying to bring back British valve production in case you hadn't already heard. They'll always be a market for valve amps, theres just no soul in a fucking kemper 😆

@fongy200

2 жыл бұрын

That's right James. I use a Kemper but you can't beat a valve amp the Kemper for me is convenience. My AC30, JTM45 and other amps that are valve state along with my Guitars are my pride and joy. I agree there's no soul in a Kemper it's an amazing piece of tech but there's something not included with modeling gear. I like yourself am in the UK and I've been using a load of nos Mallards and Sovteks that I got from an Auction, massive job lot all sizes, I proper dropped on they came out of an old Radio Rentals store in Mold, Wales from what I can gather. Anyway sorry for the waffling but I agree and the Brimar's are decent valves.

@nickdevriese

2 жыл бұрын

Really? Brimar is coming back? Nice.

@jameseberhard7457

2 жыл бұрын

@@nickdevriese hopefully so mate, they have started producing ecc81s in the britian I think, so hopefully they'll expand the range to include so more common models

@jameseberhard7457

2 жыл бұрын

@@fongy200 that's it man nothing can replace the experience and inspiration attributed to playing a big bold valve amp, the spirit is what makes the music, musical

After looking at your scope waveforms, I am concerned that one half of the push pull stage is going into clipping before the other one is...so you may have one tube doing all the work on 1/2 of the push pull output, or possibly an output transformer problem. The best thing to do to troubleshoot the problem is to look at the AC voltages across each one of those 4 cathode resistors to see if one or more are way different than the others. That could end up being something like a screen resistor that overheated and changed value, or it could be unequal outputs from your phase inverter stage that drives the grids of the output tubes. In any case, you will have to drive the amp into non-symmetrical clipping, (not square wave), and look at some waveforms to troubleshoot and repair.. And pray that it is not a shorted turn output transformer problem causing unequal loading of the power tubes. In any case...... It looks like you may get to produce at least one more episode regarding this amp repair on your KZread channel..., and I will be looking forward to watching it...

@SIXSTRING63

2 жыл бұрын

Exactly! Just had that happen on an Orange Dual Terror. Easy test proved my theory. Unhooked all output transformer leads from amp, injected into the secondary a 5Vac swept sine wave from 30Hz-4Khz, used two channels of my scope with each lead on the two primary leads with ground on the center tap. Right away you could see one side was way uneven in amplitude from the other with notch distortion on the low amplitude side. Amp has shorted a tube, replaced tubes and would only push 6-7 watts maxed out when it is rated for 30. After checking all the obvious I tested the output transformer and bingo. What a time to find some of the right impedance, physical size for a lunch box amp that would put out 30 watts. Mojotone had a Trainwreck style output transformer that I made barely fin for $95. Either that or order from Orange and have it shipped from England. I bet it would have been $300 with shipping and duty tax……….. works great now. I bypassed that 2/4 tube switch too. Flicking a switch with 330v is just asking for trouble. Should never be switched only while off or in standby. Most players don’t know better and just do it anyway. Switch was jumping all around on resistance with meter in one position. I bet it arced internally. Has a half power switch for the output anyway, how many attenuation does one lunch box amp need. Hitting 32 watts with this new transformer. Personally with all the new tubes, caps and transformer you could have bought a used one. Terrible build quality, more Chinese junk. Just need to up the cathode bias resistance a bit. New transformer upped the B+ a bit. It was on the edge before with 120 ohm resistor for each pair of EL 84’s. RCA manual calls for 150 ohm minimum. I think I will try 180 ohm. Right now it is at 15 watts max dissipation. Need to get it under 12. Guy had a half dozen used tubes in amp soft case. Obviously been eating tubes. Orange didn’t design this amp well at all. Hopefully I took out some of the questionable design choices to make it more reliable.

Hey Brad, could you show us how to add a tube reverb circuit / tank to old tube amps ?

@highpath4776

2 жыл бұрын

Uncle Doug added a reverb (one on a new build, one on a amp that had a spare switch hole avalible after a mains tidy up)

The Tung-Sol 6550 is rated at 42 watts plate dissipation. Russian tubes often have less than optimum vacuum. As you increase bias to reduce plate current, you are also increasing the plate and screen voltages making it more likely to internally arc. To be safe, lower the plate and screen voltages, or at least the screen voltage because the screen cannot handle the higher voltage as well as the plates can. Burn-in is a very good idea because when the filaments heat up the cathode it activates a 'getter' material designed to remove any residual air and any new air due to tube pin seal leaks. Remember that the Marshall was designed back when most of the ac power outlet voltages across the US was only 107 volts. Now it's at least 10% higher. That means the plates and screens are operating at voltages that are 10% higher.. 400 V becomes 440 V in the HV supply. The best all round solution is to purchase a 12.6 volt CT filament transformer rated at the same current as your HV fuse. Hook the primary of that filament transformer across the HV fuse line, and then by choosing the phasing of the secondary windings of the added transformer and placing them in series with the primary leads of the Stock Marshall transformers, you can boost (raise) or buck (lower) the ac voltage going into the Primary windings of the Marshall stock transformers. 120 vac in - 12 vac bucking (out of phase ) voltage from the added transformer will give you the 108 volts the Marshall was designed to run at.. With the additional transformer you will be able to boost the line voltage by 5% or 10%, leave it stock, or REDUCE IT by 5% or 10%..... If you have weird intermittent tube problems in the power stage, buy yourself some 1 ohm 1/4 watt resistors and put them in the screen and cathode connections to EACH TUBE.. The idea being that they burn open before the tube destroys itself (or immediately after but hopefully that will not be the case. Next time a tube fails look for the exploded 1/4 watt parts and it will point you towards your cause. I would also replace that bias potentiometer on the off chance it was getting intermittent... You can also raise the voltage at the center tap of the filament transformer by using a voltage divider to raise the filaments to 50 or 100 volts above ground using a voltage divider off the high voltage power supply. . There's all kinds of things you can do to make those tubes work, but by far the simplest and easiest solution is with the addition of a buck/boost transformer... (it's like turning your variac down from 120 vac to 114 vac or 108 vac) You only need a high current transformer, (8 to 10 amps,) for that Marshall amp because it's high voltage transformers were fused at 8 amps, which sounds really high....... In typical guitar amps a 2 amp transformer is usually big enough.

@ghramsey1681

2 жыл бұрын

Great idea with using the transformer to "subtract" input voltage. I've built a portable version. I housed it in a box with a plug so I could use it on anything. I'm a tube amp enthusiast. Got into rolling my own for personal use. Small amps for hobby use. In 2013 I got an Ampeg J15 that is from 1960 at a yard sale from my across-the-drive neighbor (I'm in a condo) for $20. It's the 2x6V6 model not the rare type. It had 1/2 open OT, needed a cap job and proper 3-wire cord. Our line voltage here in Houston tops 121V and higher. I used the 12.6 V3A transformer to drop that 121v down to 108-109v. Works perfectly.

I am a bit confused. so the problem wasn't with the tubes?

@Fixologist1

2 жыл бұрын

The tubes did fail under a bias setting where I would not have expected them to fail. The customer was cranking the amp and using an attenuator, which was pushing the amp into dangerous levels of dissipation. I believe it was a combination of things.

My 1996 CD player power supply (aux, the audio supplies are good) brew it's fuses last night.. I feel your pain..

It's blowing 6550s because it wasn't designed to use 6550s and definitely not KT88s!! 2203s and the transformers were designed for EL34s. It was only when the quality of EL34s and high fallout, that Marshall had to scramble to get product continuing to flow out the door, so just dropped in 6550s. However the transformers can't handle the current draw, so if you use them, you have to bias them cold! Likewise, lay people that are naive and don't understand the engineering behind it, don't realize the output transformer is designed to match the vacuum tubes for ideal loads. However, the ideal load for 6550/KT88 is double what an EL34 is (5k v. 2.5k), so when using an 8 ohm cabinet, you can't or shouldn't have the impedance on 8 ohm, and it should be (i forget which way to go with it) 4 ohm or 16 ohm setting, but NOT 8 ohm!! Use the proper tubes (EL34s) and bias them correctly and you won't be stressing your amp and transformers and blowing shit up, it's THAT simple!!

Great Work and Damn Sure a great channel

I’ve worked retail my entire life and one thing I’ve learned is it’s easier to keep a customer happy than trying to get a customer back! Should’ve reimbursed you for the tube,it wouldn’t have cost them much at all and you still would’ve bought from them.

@TheGuitologist

5 ай бұрын

Correct. They’ve missed out on probably $2000 worth of business since then just from me, not to mention lost business from those who would have bought from them upon my recommendation. I never even mention their company name anymore.

Awwww. That phone talk reminds me of IT people playing pranks on tech support scammers.

Can you tell is the client is exceeding the load? Like 4 ohms on the 8 or related? I understand more things should fail under overclocking amps, been there....

@TheGuitologist

2 жыл бұрын

I asked. He’s using 16 ohm cab.

@electroKrunch

2 жыл бұрын

@@TheGuitologist That's sure not gonna stress it... thought I'd ask... bummer on the wholesaler

Those bias resisters were probably replaced by the importer when they changed the EL34's out for the 6550's

@alwaysopen7970

2 жыл бұрын

6550s were meant for the USA market as the EL34s didn't like the boat ride across the pond.

@Cpt_Adama

2 жыл бұрын

@@alwaysopen7970 During that time period they were having major quality control problems with the EL34's even before they came across the pond. After the importer started having to replace tubes all the time they decided to go with the 6550's which required a bias resister change. So they came over initially as EL34's and before they were sold they changed the bias resisters and the tubes.

I agree with other comments about an ultrasonic oscillation. I've spent years rolling my own guitar amps as a hobby. I have built mostly low power circuits which could be very unstable on home made chassis. And my spaghetti wiring never helped. Using a 12AU7 or 6SN7 as a power tube for a whopping 1/2W power output. But through an efficient speaker it's loud. Anyway, I have experienced issues with blown fuses to a lesser extent. Could be getting grid conduction too which would draw large amounts of power through the power tubes. Hopefully the OT is not at fault as someone else commented. That is tough to tell unless at full power with guitar on it. The signal gen might not do enough. Maybe isolating the OT with a signal and scope would help before expending more tubes on it. That wave you saw in the flashback though was indicative of oscillation, but because it was on the CF it might have only been related to impedance with your scope probe on that position too. Especially since chop sticking it fixed the issue. You were measuring total cathode current with screen current included. Check the screen current and subtract it. See if the screens are perchance drawing excess current. IF there is ultrasonic oscillation going on that could contribute to the current draw total. Measure the drop across the screen resistors.

Did you see the resistor that was damaged? 47k?

Man, I don't want to see you pissed! I want everybody to be happy all the time! You know, kum ba ya, Don't Worry Be Happy, & sh!t like that..

Could it be ultrasonic oscillation? The " Flashback " video makes me think oscillation. Now why it goes away as volume goes up is interesting, but still a possibility.

@SIXSTRING63

2 жыл бұрын

I saw what looked like parasitic oscillation too in that earlier video. He needs to invest in a cheap digital scope to freeze frame the trace and zoom in and see the oscillation and the frequency. You can get a decent new digital scope cheaper than a beat used 40 year old Tektronix scope. I have two nice old Teks I love but use my Rigol 1054EZ for zooming in on noise. I love all the read outs the new scopes have too.

Fun. Will have to catch it in the morning. 🧘‍♂️

Aloha from Hawaii it was great to see you take a full circle you wanted those tubes and they wouldn't give them I realized to observe pain in the ass you never know one blows it f**** the rest but it was great because they turn you down and then you realize you know you weren't going to get it we all were rooting for you