Hi. I am Chris, The Guitar Amp Tech, working in Sydney, Australia. If you have a vintage valve amp, a modern valve, or solid-state amp, I will get it back to sounding its best for you.
I have some famous customers, but most are weekend warriors, like me, who are just as passionate about their sound. I also do repair work for major Sydney music stores.
There are a lot of myths in the amp world. I will do my best to address them as we cross them. Likewise, if you think I’m talking garbage, let me know.
I did my Electrical Engineering degree at the University of NSW. When I was 17, repairing my amp was my major goal in life. In some videos you can see that first bright green paneled Savage amplifier. It still doesn’t work!
Every 2 weeks I will be uploading videos of my more interesting repairs and offering some insights along the way. Some videos are short, some silly, and some detailed. It depends on time between repairs and the amp which inspires me to press “Record”.
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?Where did you purchase the 3 connection star ground terminals? Thanks
Is it the resistance of the steel that causes the noise when they go directly to the chassis? Would this still be a problem with an aluminum chassis?
Good one Chris! I heard or read somewhere that the piano wire link between the pots was mainly to stop them rotating if their mounting nuts became loose? But I'm not sure. Does that link wire separately connect to chassis earth? - I couldn't see. What wattage iron do you use to solder the earth wires to the chassis? I bought an 80W iron from ole mate Jaycar electronics, which was the highest power iron they make, hoping it would be enough. I used to have a 250W iron with a 1 inch diameter copper tip! - Which unfortunately got incinerated when a firestorm burnt my sheds down, & nearly my house along with them. Those Vishay metal films sound like a great choice mate! - As do the fnt (?) filter caps. I like your idea of grinding down a metal nail file for the phone jack contacts. We won't tell the missus! Shshh! That original V1 was definitely kangaroo Edward, as well as not knowing the words! Did I miss the the point where you said a bit of assymetry gave nicer 2nd harmonics, but then you said the 27% difference in bias was no good? I missed the nuance there! Loose bolts all over the place was a bit of a surprise, but good thing you checked em & tightened em! Maybe a bit of nail polish might help ya reckon? Nicely done overall & you should have another very happy customer! Liked the "back in black" & "baby please don't go" sound test! - Noice!
I have a clone JMP 50 built here in NZ. Sounds great, but I am always looking for improvements or tweaks to taste. Grounding is something I'll check now. Cheers. So far all I have changed is I've split the shared V1 cathode, so it has the 0.68uF and 2.7K setup on V1b. I have also tried changing that coupling cap between the first two tubes. 0.0022uF instead of 0.022uF. I am not sure I'll keep it that way, plus I like the look of the mustard caps it came with. I've also tried various bright cap values. All pretty basic stuff. Maybe the biggest improvement was had by trying the various preamp tubes I have. Just looking for the least noisy combinations of them in all three slots. That and sourcing some tube shields for them helped with noise. I'd like to find a good 7025 tube. Supposed to be very quiet in V1 but still sound good. Once I got the preamp noise down, the presence control is less prone to oscillation when everything is turned up (still scratchy though, but that's normal for this design apparently). Power valves are Mullard reissue EL34. Seem pretty good so far. I have a pair of those old Sylvania 6CA7s like Van Halen used. Last time I checked they were barely within matched, so I do not like using them, plus I do not want to use them up for everyday use, because they are very rare now. It did not have a head cabinet. I ordered one from Ceriatone, but it does not look right. Ones that do look right from the USA tend to cost almost as much in shipping as the cabinet itself. Stuff that. Not sure what to do. Sometimes I think about converting it to 2204 spec, but then I think nah. Having a good sounding Plexi is nice to have, so why change it to something else is what I think. Then i toy with the idea of build a MKII master volume amp. A little above my pay grade yet, so i think I should build a 5F1 amp instead.
Good job Frend.
Thank you, Miguel!
Did you end up changing the el34s?
Oh no! Don't tell me I edited that out in my desperation to shorten the video. Yes, I changed them. If my memory serves me well, and it usually doesn't, I used TADs
My next amp is going to be one of these, or a 2203. Gotta be a JMP, my favorite Marshall aesthetic by far.
Both are great amps, Yeatzee. Enjoy them. Sadly at my age and gigs, I am regularly told that my Marshall 1974 18w is too loud.
@@theguitaramptech yeah attenuator definitely in the cards regardless, but we play pretty loud
Great job my friend. I have always been able to improve the noise floor on older Marshall’s by improving the grounding in much the way you did it. Cheers.
Great minds think alike!
I bought the combo version of this amp new in 1977. I was new to the guitar and it was my first tube amp. Sadly, in 1978, I sold it to buy a solid state amp with more bells and whistles. Though I still have and use the amp I replaced it with, selling that 2104 is something I really regret. Not to mention that now it would be worth 5 times what I paid for it in 1977. Glad to see some still out there and being taken care of.
Yep. The prices these fetch, especially in Australia, will make your eyes water.
interesting you grounded the middle and presence pots to the reservoir cap ground. i never tried that. What would be the difference grounding those near the pots on a ground lug to chassis? (not to drill a hole for this amp as it is vintage)
Sure you can do a separate ground; it would be better than stock. The biggest improvement is just separating the preamp and power stages. Lyle @psionicaudio has an excellent video on grounding for Marshall amps. Check it out.
@@theguitaramptech i normally go with the Larry grounding scheme with the exception of the heater CT, i don't ground that at the input jack
They're a fantastic circuit!. Jolly good show, legend!
Thank you, my friend.
Hey Chris, where are the screen resistors? 33 minutes into the video and I keep looking but I just don’t see them. Are they hidden?
I assume you mean the grid stoppers. No, these amps didn't have them. I think they're a good idea, though.
@@theguitaramptech no the 1k resistors on the power tube screens. I don’t see them but they’re on the schematic you show at 22:01 in the video
@@ampyamps I recorded this repair back in the Aussie summer (its mid-winter now), so I can’t recall amp specifics. However, I can tell you that earlier Marshall models did not have screen grid resistors. If this was the case here, I would have decided not to install them as changing screen grids can have an impact on the tone of the power stage. Thank you for noticing and commenting.
A beauty. What's your experience with those impedence switches? I've seen them for a good price but didn't know if they could handle current.. I've tried the alpha ones as well, and they worked, but then I read they also are questionable. There's a 20 dollar switch I've used as well, but I don't particularly like spending all that much if i don't have to.
Please don't skimp on Impedance switches. You don't need me to tell of the consequence of failure. I found 2 replacements in the past, neither of which fit properly without some convincing!
@theguitaramptech thanls for the reply..that's what I thought, lol. The switch in that marshall is a knockoff of a lorlin switch. A lot of the Diy Dr. z airbrake clones have them, and I've never been confident they're safe.. the alpha ones scare me too , ha. Although I've seen a fryette video where he's looking at a marahall that Dumble worked on and he used one, jumperibg each gang for more current handling. But when you look up the current rating on those, it's super low. I guess I shouldn't skimp on that particular part , as you say.
Hi Les. Yes, it's good to be doing another video. I have been so squashed with repairs that the videos have taken a back seat until I am more caught up. Thank you for asking about my daughter. We’re all going well, thank you God! I use a chopstick to hold the wire in the solder puddle to make the best connection. Some insulation gets a bit soft when using the high-heat soldering iron. It’s a sound connection.
It's great to see you back making videos Chris. I hope you and your daughter are OK. Another great video. It looks like your soldered earth lead got squashed a bit!
One two of the reasons I watch your videos is you are very good and I get a kick out of your deep down under south Australian demeanor and speech accent. And is slightly salty at times with good humor.
Thanks mate! Great to hear from you again Dwight.
The thing I like about Australians is they seem to be friendly and have good conversation. My call sign on ham radio is KC4ITU assigned to me for my government apart an agency called the FCC. I was on a band one day cold 40 meters a bit above 7.15 megahertz talking with four gentlemen back in the year 2004 one man was in Melbourne Australia another cook Island in the middle of the Pacific Ocean another one in New Zealand and the 4th Gentleman on the island of Hawaii I made contact with them was about 600 W of power and using a modest antenna. We exchanged with each other Fair signal reports and after a few minutes the Australian gave me a call and said he recognized my name and used to know Dwight Eisenhower one of our former presidents back from the year 1950 that surprised me and my jaw dropped to the floor in amazement very nice contract from your country to mine I thought it was very nice I signed with them after a while thanking them for their conversation such fine gentleman. Thanks for your reply Chris. You are a fine gentleman as well.
Thyats bettah.
Close Dwight ... but not exact. Next try a phonetic spelling, the same as "bettah" but with no "t" sound.
Never seen one before. Nice video!
@@TheGuitologist thanks Brad 🙏 Yes, they’re British. Thunderously loud with fantastic cleans. They were around in Australia in the 70s until by Laney took them over.
hi Chris great information on cross over distortion.
Great work. I had an older HRD that had the +/- 15V dropping resistor overheating and noisy channel switching along with an ultra-sonic oscillation at about 22 KHz that was sensitive to presence control setting (negative feedback) and tube socket flex circuit positioning. It required adding series resistance in the tube grid circuits to kill which was not easy. I think we all should be more vigilant in routinely checking the output with a wideband scope.
Nice job! Would’ve been fantastic to hear the handwired ‘64 DR in comparison. Maybe it wasn’t available at the time. Thx for the great comparo.
Yes, it would have been great to have a real '64 in the workshop. You can't plan these things. Of course this week I have two original '64 Deluxes belonging to an Aussie music legend (who will go unnamed). I am making a video of the repair of one of them...after I finish two Victories, a 100w Bassman and a Blues Deluxe. Phew!
Great video and explanation Chris. At 58:50, the 2 tubes magically insert themselves.
I love magic tubes, Erik!
soddering iron, snozzoramus!
HAHAHA!
Just got blown away listening to Lemmy playing bass with Hawkwind and looked up his amp preferences - the Super Bass was there and I could also find the schematics. Your walk through of the circuit and explanations were excellent and there is always time for The Who!
Thanks mate! Love The Who
awesome tone
Agreed. Delicious, rich and 3-dimensional.
Great video..I have three H&H amps 2 are valve sound and one PA amp..One of the valve sound amps has a very low volume. what can cause this ? any help would be great..regards.
Wow! A valve HH! Very cool. The best place to start is the power supply. Find a schematic and check that your voltages are close. Then try a different set of power valves (don't forget they will need to be biased).
@@theguitaramptech Thank you for your help..best regards.
i could be wrong -BUT - the mentality at artist seems to be - keep the PROFIT down -but high turnover .....or maybe its just 3 rd world exploitation !! LOL ......but i love what artist have been offering - in the late 70s and 80s ......even crap was expensive.... so many options it allows you to try other types of guitars and instruments - love artist AND....they are very professional too
Thanks for your message Michael. Ian Bush (CEO) is a very clever man. Think about how many hands a Fender guitar passes through from the Factory to you, each one adding to the price. Ian Bush sources products directly from the Chinese factory AND has them made to his specs. The quality is ridiculously high and the price is ridiculously low.
Why would you use a Weber speaker instead of a Jensen P8R? I have done a lot of testing and I have never found a Weber that sounds better than the Jensen RI. I am curious.
Hi Voluntariast. Thank you for taking the time to share your thoughts on speakers. Fortunately, tone is SO subjective that we can have no argument. To my ear, Weber speakers are the finest handmade speakers available. I have them in all my amps (except for my 1968 Princeton where I managed to squeeze in a delicious Celestion Blue). The Italian production Jensen P8R is another fine speaker choice and is certainly cheaper (in Australia) than the Weber option, but to MY ear the Weber sounds better. I am happy to see you prefer the RI Jensens. It means you have ears and don’t simply follow the speaker fashion. Vive la difference!
@@theguitaramptech Interesting. Thank you for your reply. I am not even sure I trust my own ears so I bought 2 Jensens reissues and 2 Webers and recorded them and too me the Jensens were much better. But as you say, 'to each their own.' Thank you for your interesting video. I have the same amp as well.
@@TheVoluntariast That's a perfect solution. You put your money where your mouth is and listened carefully. What could be better for meeting your musical goals?Well done, mate. And congrats on having a gorgeous amp!
I have the bassbreaker 30r.is the circuitthe same.I have 2 tubes of the four red plating
Ouch. Good luck
The tone of your voice said it all but when you showed the camera, it turned Into a proper horror show. I’ve heard this practice referred to as “shotgunning” an amp.
Shotgunning is used by some "Techs" who don't know how to test components and have little understanding of the son of the consequence of their approach. A capacitor is NOT a capacitor. If they were the same, everyone would use those cheap plastic green caps. Sadly, there is no governing body to be an amp tech.
In the early 80s we went to rehearse in the basement of a HH "shop" in Holloway Road, London.... it was so damp down there, it was hard to breathe, we left after about an hour 😂
HAHA! What a great anecdote. Thanks for sharing
Harsh criticism of one of the most significant amps in the history of electric guitar. Who last touched that amp? Clearly, parts have been changed. A thoughtful technician may have asked the owner if he wanted the "tacky graffiti" removed from the chassis...considering those markings were left by the founder of Mesa Boogie, Randall Smith. I'm curious how much the removal of the factory markings devalued the amplifier.
I just scored a sweet 68 Princeton. It literally just arrived here in Detroit Michigan from Nashville Tennessee Thanks for sharing this video sir. I've no doubt I'll be referring back to it soon enough. Fender Amps are the best!!!
Good luck Michael! I Hope my video will be of help.
Demo it with a multy effect board. The way to sell is make the product sound the best it can sound with very good playing just as a thumbs up
That trem sounds bloody beauty bonza, mate!
It was just so lush, Brad, I had to rush out and buy the JHS Harmonic Tremolo pedal. Noty as 3-D sounding as the original, but better than the on/off later Fender tremolo. Hope you're doing well, my friend.
Wow, now that is what I call a amazing sounding amp !!! Brilliant work Chris 👏👏👏👏
Thank you, Pau; I love this amp!
Me too. So much that I am very tempted to try and build a clone of it !! I saw a demo by Johan Segborn of a 6G5a which was equally amazing sounding. Was that the Italian Jensen that we hear in your sound clip at the end or the original ?
It is weird how stupid some guys are about the parts in their amp. The caps are 50 YEARS Old...... if bot now, when..??? And..... if he replaces ONE, your amp is no longer "Original"..... so why not replace the rest of them. There is NO Magic in parts. They are there to perform a certain job at a certain voltage. It does not matter if they are Blue or Yellow, Carbon or Metal, Oil or Plastic. This amp does NOT sound "original" with 50 year old Elytics. But it WILL sound original with new filter caps
Yes, many people share your point of view. I just happen to not be one of them. Briefly: Your sound does not pass through electrolytic filter caps, so change away. Your sound DOES pass through coupling caps and Blue, Yellow, Red or Green don't sound the same. If you're not sure about it, try replacing all of the coupling caps from YOUR old Fender with the cheap green poly caps from a hobby store. You may not hear the effect of one capacitor being changed but you will hear the combined effect. That's why shot gunning an amp will ruin it.
I'm very reliant on visual learning and your presentation helped me a lot. It is difficult to navigate through the jargons sometimes as an aurally challenged person.
Thank you for your kind words. I am very happy that I was of some small help.
Thanks for a great posting ! It is amazing how people will fix what is not broken with strange mods instead of just buying a pedal and building a pedal board. Every single Marshall is different, and sometimes Hi Watts take pedals better than Marshalls. This tech is a real pro.
Thank you for sharing. Amps, especially as they age, have different components drifting at different rates, or even failing. This certainly can make vintage amps sound unique. Good point. Its another reason why I never "shotgun" an amp with new components (unless they have failed or drifted too far away from spec).
Hello! great video! I am about to get a bassbreaker 15 in a trade and was just looking up serviceability. I'm no tech, but I am curious and like to get my hands dirty (without getting electrocuted) :) . Out of curiosity, did you completely remove the diodes? or literally just clip one leg and leave it in there? Is simply clipping them ok? or should I consider removing them with the iron? Thanks! Awesome content!
Hi Pedro. Clipping it out is sufficient. The BB15 sounds excellent but sh*t to work on! Good luck
@@theguitaramptech thank you! :)
Fab videoo Chris..What a master tech you are..🙂 Just learn so much and your attention to detail is great..Thanks for sharing😊, and it sounds perfect..Great playing by the way..Ed..uk..Stay safe man..👍( Both mics sound fine, I'm leaning towards the Shure..🙂)
Thanks Ed. Comments like yours keep me going, my friend.
Uncle would say go grab yerself a beeer.
I look forward to sharing a beer with Doug one day, Dwight. You should join us!
LZIII
I would not expect a less noble suggestion with a name like jbonham78, in memory of the best of the best.
Crimes against humanity
You share my pain, friend
RCA. does that mean radio corporation of Australia. Or radio corporation of America. Haha just a little teaser. Chris you are a meticulous repairman tech. On amps. I see you enjoy yourself very much. Between you. Uncle Doug and Terry dayton in Grand Rapids, Mi. Iv seen alot of very good information. Thank you for sharing your knowledge. If any one needs knowledge its alot of young people today. Iv looked up a few things on Utube to repair some things around the house hear. Keep up the good work. Dwight.
From memory they were about $18 each. I got them from Evatco in Qld, Neville. Expensive as gold...but I wouldn't use less in an amp like this.
I always tell people to look up repair videos before they buy an amp. Fender amps of the last 30 years are truly disgusting. I've even seen a Handwired deluxe reverb that was pitiful. God bless you.for helping that customer out. I can imagine they aren't fun to work on. This thing is just insulting. Damn
thats a great suggestion. I did the same thing when I needed to buy a new coffee machine. I called the Coffee machine repair man.
G'day Chris. I always fancied a 1 x 6L6CG amp to go with my 1 x 6V6 5F2A tweed Princeton clone so I gave your Tweedtone 12A a go. At that price it was hard not to. I've made some modifications for my own personal taste. I play rootsy blues and country and love vintage Fender tones. Not so keen on blues rock and rock sounds for my own playing. I've never liked closed back cabs, so I converted it to an open back like most old Fenders. Modern Chinese tubes don't do it for me either, so I replaced them with some nice NOS tubes i already had stashed away. Both of these changes were big improvements to my ear (perhaps not to some-one else's) but I still wasn't enjoying the 70/80 speaker. I ended up making a conversion ring for a 10 inch speaker (just because that's what I had available) and it ended up with a McKenzie 10 inch. My 5F2A also has a 10 inch (Eminence alnico blue frame). Now the 12A has more clarity than before and is a much better fit for my personal tastes and music style. I can switch between the 2 amps and I'm just as happy with either. They are subtly different but with the bright switch off and the NFD defeated (my usual settings), they have a similar feel. Of course the 12A is significantly louder, whereas the Princeton can get into power tube overdrive at lower volume. You've done a great job, especially with having to meet Artist's price point. You've clearly got the circuit right.
Very cool. I think the tube upgrade would have been worthwhile. One day, try replacing V1 with a 5751 and please tell me what you think. I don’t think any of my amps have a 12AX7 in V1. But, a good NOS 12AX7 would not sound as fizzy as modern versions. Personally, I prefer a 12” speaker, which is one reason why the TT12A was developed, but I am very much enoying the 10” Weber in my AC10. Thank you for sharing your improvements. I love the way you have used it as a platform to find your sound. Well done!
@@theguitaramptech Cheers Chris. I would have used a 12 inch speaker if I had one that I like and I might still go down that road if the right one comes along at the right price and the right time. I seem to gravitate towards 10s though. That's just me. I do have some GE 5751s somewhere. I might pop one in later. As you know the 50s Tweed circuits were classics, so the fact this amp holds its own against a 5E2A says a lot.
Good vids, however, it amazes me how many techs call out amp parts like caps and resistors incorrectly. Such as a zero as the letter 'o', ie .oh47... Other than that great job...
A colloquialism used on an entertainment platform amazes you? It's no more consequential than your comment referring to a capacitor as a "cap" or an amplifier as an "amp". We all know what you meant so there's no problem. It's not like someone can buy a "point oh four seven cap" where it would be the incorrect part because a "zero decimal zero four seven microfarad capacitor" wasn't used.
@@stevencraig I made that comment as a person that made a living working on software and computers. That industry taught me to properly call out 'number 0 as zero' and 'letter O as oh'. Mix those up in the IT field and things go bad fast... I did not mean any disrespect, matter of fact these amp techs have my complete respect, at least the good ones I follow...
Great point
So was I right about the power transformer being original..?
Of course you were right!! I should never doubt you.
Playing devil's advocate here... Is it possible that this amp originally had the older Astrons on the eyelet board? If so, changing them out wouldn't have been as big a deal. Have seen other brownies with those in them, but you've been around a lot longer than I. Thoughts?
Hi TK, yes this amp may have had the Astrons, but from my experience, I have only worked on Brownface amps with the Blues. Even if they were the Astrons, I would still take exception to changing them all without testing first. I left 2 Astrons behind in this amp as they tested fine. If they lasted 60 years, I am not expecting them to fail in the next 6 months. And then there's the question of the missing output transformer. Sure they can fail, but how many vintage OTs have you changed? I can't remember replacing any in a vintage Fender. But excellent point, TK. Thank you.
@@theguitaramptech Yep, of course - totally agree with you there. A motto from one of my favourite books goes, "Always Test Everything!" I've only had one failed vintage OT so far - a Moody 1712 Vibrolux - 1/2 of primary went open under test. It was like watching my favourite pub burn down. Thanks for sharing your work and ethos. Cheers mate