Hey guys...thanks for the overwhelming response to this one. I've gotten a lot of questions regarding what was the final diagnosis because apparently I wasn't clear enough in editing. The switching transistor TR1 was faulty. Replacing that allowed the Boost Channel to come alive. The phase inverter tube, V5, was causing some sort of issue as well, as was shown in the video, so it was replaced. It tested good on my tube tester prior to troubleshooting. I edit out tube testing from most videos because it gets laboriously long - 50 minutes even without showing tube testing is getting longer already than most attention spans. In fact, you've probably already stopped reading this. The V1 tube tested on the weak side of good on my tester, but I left it in because it should have still worked just ok, which it seemed to do because it is also part of the Boost Channel which was working before I replaced that tube. The V2 tube was the one I finally replaced at the end which allowed the Normal Channel to function properly and fully. The tube I was using in that position during the troubleshooting tested good on my tester, but for whatever reason, this amp didn't like it. The fact that it tested good on my old Precision tube tester is what led me to assume it wasn't the tube and explore other options. Also, if you'll notice on the schematic, the switching is tied into the grid of V2, which is how the Normal Channel gets muted during Boost Channel operation. My theory was that switching in the IC might have also been at fault. Anyway, hope that clears thing up for those of you who had questions. Watching the video back, I can see why it was confusing.

@daw162

5 жыл бұрын

>>you've probably already stopped reading this

@adrianshingler9783

5 жыл бұрын

The Guitologist I have only just started watching your channel but I have to say you are a star sir! I am an electrical engineer in the UK and have done a little bit of amp repair and build myself, but ultimately I would like to have a set up similar to yours. You bring wonderful old amps back to life that would otherwise be thrown in the skip so well done you hero! 😊👍. Love the guitar playing by the way. Just one question about your signal probe, as you are at plate voltages I presume you have a dropper resistor in line to protect the input of your test amp? Keep up the good work I am already a big fan!!! Keep on rocking 🎸🤘🤘❤️🎸

@johnabbottphotography

5 жыл бұрын

I believe that every repair comes with a lesson; one of those "I should have tried that!" moments. If you took away that kind of a lesson from this, what would it be? (Would it be to break out the chopsticks early?)

@grahamthorpe4256

5 жыл бұрын

ha ha ha thats funny brad my bad

@joelspaulding5964

5 жыл бұрын

Watched and read to the Omega. The knowledge and focus required to repair such perplexing issues... RE-SPECT!

I love the way you explained the proces. My kid was watching you like a hawk. This will help many many youngsters. As a DAD I want to thank you.

@TheGuitologist

7 жыл бұрын

Awesome! I have over 300 videos like this. Be sure to subscribe.

@liveatvictoria6853

7 жыл бұрын

I agree with what Frans van den Berge said, you have a way with showing on the video, makes me think you'd be a good teacher. Take Care. :)

@FransvandenBergeMuziekschuur

7 жыл бұрын

I did. Thank you.

I'd rather watch an hour long video of you tinkering with an amp than 99% of the garbage they have on TV these days. :)

@surg71

7 жыл бұрын

In a nutshell.

@rbagel55

7 жыл бұрын

The only thing I watch on TV nowadays is the News, and that is only once in a couple days, fuck the TV

@TheGuitologist

7 жыл бұрын

Yep, TV blows. No history on the History Channel. No music on MTV. Propaganda for "news". No learning on The Learning Channel.

@ellarkay9842

7 жыл бұрын

Hey! George Stephanopoulos everyone!

@johnmonroney8614

7 жыл бұрын

agreed. i threw my television in the toilet

These videos are like a murder mystery! Who dunnit? Well, it wasn't Professor Capacitor in the main board with a leak...let's try Colonel Transformer in the mains section with a short...lol

@TheGuitologist

7 жыл бұрын

Miss Scarlet Transistor is highly suspicous...as is Col. Mustard Cap's work on the classified fusion bomb.

@smacman68

7 жыл бұрын

lol This one was a doozy. It makes you wonder if you should just replace all the tubes in the beginning just to eliminate those as the culprit. I admire your determination and methods of troubleshooting

@God-CDXX

7 жыл бұрын

The highly suspicious find 12AX7A strikes again

@TheGuitologist

7 жыл бұрын

Then I would not be able to film myself flailing around like an idiot. :P But seriously, those transistors were definitely bad also. And it didn't hurt to change all those caps in the switching circuit.

@bucyruserie1211

7 жыл бұрын

Wait a min... I saw that movie, it was the guitarist from Spinal Tap in the hallway with the Beatles album Revolver! Really, same actor!

EYE TROUBLE I USE CAPS :) . I REPAIRED TVS FOR 30 YEARS AND AM RETIRED NOW . I ENJOY WATCHING YOU AND THOUGHT ABOUT KEEPING MY HAND IN REPAIR DOING EXACTLY WHAT YOUR DOING I.E. WORKING ON TUBE AMPS . I AM OLD ENOUGH THAT I WORKED ON TV'S WITH TUBES IN THEM FOR A FEW YEARS AND RETIRED IN 2005 . BUT WATCHING THIS VIDEO SAYS EXACTLY WHY I DONT LOL - I AM ENJOYING MY RETIREMENT . STILL LIKE TO WATCH YOU TROUBLE SHOOT . GOOD JOB. KEITH

The toddler babbling in the background is fantastic.

@TheGuitologist

7 жыл бұрын

She's an absolute nutcase. Takes after her mother. ;)

@mark006868

7 жыл бұрын

lolololololololol

@pwnEdge1

7 жыл бұрын

I thought she was talking about the amp, what were you saying :-)

@taterlysaladman9377

7 жыл бұрын

She is trying to tell you that British folks never understood electricity. Or maybe it was just the humidity. From cars to amps they showed their prowess.

@ronj9448

7 жыл бұрын

Live translation for "pre-school school of rock" class.

I don't understand a lot of what you're doing but I have to watch the whole thing. The suspense, the mystery! Awesome vid.

I owned a combo just like this from 1985 to 1987. Best amp I ever owned. A beast. Wish I had it back.

I salute you man! You have an unbelievable degree of patience!

THe problem with this channel is it's so addictive. I've lost about 6 hours today. Apart the educational side, I just love your accent and sense of humour (I'm in the UK and just love southern accents) . Please don't ever think of stop making these videos. Just wonderful.

Had a 2203 back in late 80's. In my case the switching IC was fried. One of my first repairs. Thanks for bringing me back in time Brad!

Kudos to you! I recently had my amp go bad and brought it to an amp technician who made it well again. Thank God for folks like you who help make things well when they go bad. Great job!

This was one of you most informative and entertaining videos. Thank you for including all of it! It is nice to see a repair that didn't come easy but worked in the end. Well earned sir!

Damn, I get too into these videos. I was stressed completely out until you figured out the problem like four minutes before the video ended. What drama!

@TheGuitologist

7 жыл бұрын

It can really suck when one has multiple issues. You try your best to eliminate variables but it doesn't always work to plan. I did test the tubes before even starting on this, but edited that out for time. Turns out, the 2205 is really picky when it comes to preamp tubes.

@johnbhumphrey

7 жыл бұрын

Not to be confused as a complaint, I didn't mean for it to sound that way. Great entertainment, that video had lots of drama. Keep'em coming.

@TheGuitologist

7 жыл бұрын

I didn't take it that way.

@hjdorn

4 жыл бұрын

@@TheGuitologistFunny how it's always the last thing you look at.

I blew the dust of this vid that I missed back then. Great troubleshooting! I get more confident about tearing into an amp I accidently misinstalled a tube in and it flamed a bit. Thanks Brad, keep 'em coming!!

As an electronics troubleshooter myself (for a living), I absolutely love your videos. Keep doing what you do :-)

It's not everyday you see a nice Marshall out in the shade, in nature. Refreshing.

i like how you go through every troubleshooting step. it really helps for others doing the same.

@TheGuitologist

7 жыл бұрын

Hopefully it helps someone. I know the clips seem to skip around a bit in this one. That's because it was filmed over several days and some things had to be edited for time, but it's essentially all there.

19 minutes in, I watched a bunch of this guys videos, I know he will get her fixed up and purring just right and he will shredd up a nice storm on it to test her out. This old cat knows his stuff and plays like a pro, don't none of ya all ever doubt him, he is the amp / guitar master! I love this guy's attention to detail and his incredible perception, he's made so many old ratty things sing like a, well a thing that sings really, Really nice...

Oh Brad, man, I think I may have been feeling your pain watching this repair unfold. I can relate to these difficult examples. Well done with the perseverance dude.

@TheGuitologist

7 жыл бұрын

Hey Dan, Good to see ya. Thanks for that. It's funny...it's like some spirit is fucking with you and know exactly where your breaking point is. The moment you get right up to the breaking point, they say "ok, let him fix it now".

Wow, that was quite a journey. I have one of these amps and after several visits to repair techs I finally gave up on it and bought a new DSL 40. Several years later now, I may open it up again and try a few things, so thanks for the vid!

Brilliant playing as well as top class repair work. When I did repairs back in the 70's there were very few circuit diagrams available. Keep doing what you're doing, I love it.

I'm a completely self taught amp tech and I've had a bunch of those "I'm completely at a loss here" jobs. I spent almost a week off and on with a repair of a simple scratchy pots job in a late 60's Univox stencil amp made by Garnet here in Canada. I initially told the customer it would be a quick fix. Oops. There was constant static throughout the whole signal chain caused by one damn 5 cent resistor. I thought it was only me who did so much head scratching. Really enjoy your videos and find them very helpful. Thanks Brad!

When all else fails, poke it with a stick.

@TheGuitologist

7 жыл бұрын

That has been my motto for more years than I care to admit. Works on women too...so I hear... :P

@donlang7964

7 жыл бұрын

My High School Electronics Instructor's Motto for working on stubborn equipment was: " If at first, you don't succeed... Use a Bigger Sledgehammer!!"

@ChrizRockster

6 жыл бұрын

Sure helps find a valve that's microphonic! lol.

@davidmoritz6972

6 жыл бұрын

You mean the Coarse Adjustment Hammer and the Fine Adjustment Hammer I assume... I used to have a large mallet on my bench which had "Coarse Adjustment" written on it in magic marker.

@Twobarpsi

4 жыл бұрын

Or hammer.

Using that chopstick reminded me when I was a kid I was given a neon transformer. A guy at my church was an engineer with Muzak and he told me how the make a "JACOBS LADDER" thingies like in those old horror movies. He told me what NOT to do and warned me to be careful. I followed his directions and after adjusting the distance of the wires it was working. He told me if I stuck a wooden dowel or something non conductive between the wires, the spark would stop there. Only wooden round thing I had available was a pencil. I received a quick lesson that graphite can be "conductive".

I know squat about guitars and even less about guitar amplifiers, but you made the process more entertaining & engaging than I would've expected...not least with your brief play-test at close. Thanks for the ride!

Dude your videos are incredibly informative to someone like me. Appreciate everything you do and how in depth you are!

@TheGuitologist

7 жыл бұрын

Don't lie, you just want to see me go ape and smash stuff. :P But seriously, thanks for saying that. Much appreciated.

@elmerfuddski1929

6 жыл бұрын

kylendm I

Sounds great dude!!! Love that crunch and midrange!!

@TheGuitologist

7 жыл бұрын

That's the Metal Gods tone, man. Gotta love it.

Love the thrash playing at the end once you finally get this thing working! Sweet.

Great vid Brad,you go at those amps like a well focussed laser.Love looking at and hearing the Junior too.I am jealous.Thanks again man.

Each video is a learning, and proof that the Guitologist, is a great luthier! Congratulations on the great job! From Rio de Janeiro, Brazil.

I studied electronics in votech (high school)... I passed the classes with a C... I knew then at 17, I would never do this work for a living. I became a Main Propulsion (Steam) Engineer in the Navy... the system drawings were just as complicated but the components are a lot larger, and easier to troubleshoot. 20 years was a life's work. LOL I did follow what you were doing and finding but had no clue as to what was needed. GOOD JOB!

@TheGuitologist

7 жыл бұрын

Thanks, Randall. Sounds like the spark may still be there in you.

For having no background in electricity except a little DC theory, you sure have whetted my appetite to learn this circuitry and everything with it. Voicing your train of thought sure makes me feel like I’m learning something. Wish I could go to school and start all over again!

Dont let it drag you down -awesome video - thanks for your efforts

Hey, a new subscriber here; thanks for taking all the time to video, edit and upload this info...I REALLY enjoy your videos!

I had one of these amps years ago and really didn't like it. It had 6550 output tubes that really are not appropriate for guitar. Marshall made their sound with EL34 outputs. Back about 20 years ago, I saw a Crate Vintage Club amp for sale and I went to the seller's home and demoed it. I was blown away by the tone and, after a short conversation, we agreed to an even exchange. At the time Crate was still make these amps and they had a good reputation. I still have the amp all these years later, but it does require periodic trips to the hospital. At this point the tubes have been replaced multiple time and all of the caps were replaced about 5 years ago. I think my problem with the Marshall was having only one speaker - it sounded much better when connected to a 212 or 412 cabinet. Not to give up on Marshall products, years later I bought a JCM 900 50 watt head and traded for a 412 cabinet. I was very happy with the way that amp sounded. I sold it about 5 years ago when I was moving along with most of my other amps, B-3, etc. I don't know why people trash the JCM 900 - I think they sound good for rock. The JCM 800 and 900 can be traced back to the Plexi, but Marshall stopped manufacturing point-to-point wired amps around 1972, so the DNA is there, but not the mojo. I really don't think tube amps are happy using circuit boards where the tube sockets are mounted on the boards, These amps are difficult to service and sometimes impossible to fix.

You are like The amp detective... love your videos!

@there_is_nothing_here

7 жыл бұрын

The Amp Whisperer

@camberwellcarrot420

6 жыл бұрын

CSI Kentucky...

I have had the 4212 (50W 2x12 Master Volume) combo from new in 1984. It's never let me down and I only work a few miles from the Marshall factory on the rare occasions when I need a retube or a refurb. The last job was new corners, new handle, new Tolex, new fret cloth, new feet. She looks lovely, but still sports some battle scars.

@hadleymanmusic

6 жыл бұрын

Alastair Archibald do they cater personally to customers? My jcm900 mk3 was stolen I would like another un abused head.

Remarkable ! Wish you lived in the south of France...I quake with fear when I hand my amps to the local dealership/repair dude... Keep up the good work - with all these tips and ideas I'm picking up maybe I'll be able to pass on the dealer and have a go myself...well maybe not...always a pleasure to watch.

Finally subscribing to your channel. Love these videos! Feel like I'm learning a bit about amplifiers and electronics just watching these. Obviously not enough to do my own repairs, but at least it's giving me some idea of what issues to look out for in tube amps!

Another amazing video. I always wanted to do this kind of stuff but wouldn't know how to get started. I can't wait to watch it again.

Nice job man, that took alot of patience and knowledge!

I just got the 5210 out of the shop. Had to disconnect the reverb circuit off the board because of bad design causing noise. It sounds very similar to this. I have an Eminence Texas Heat 4 ohm on the way to upgrade the speaker and I'll be done bringing a 1985 Marshall back to life that somebody on Craigslist sold me claiming "no issues". Haha $300 for the initial Waffle House pick-up from an unknown man in a pickup truck, $200 spent in the shop and $100 on a Texas Heat upgraded speaker. I now own the world's most expensive Marshall 5210. Still less than half of the price in 2021 than the 4210 currently. Priceless.

These videos are great. I'm learning to do my own guitar and amp work and these videos are really interesting to watch.

Congratulations. Nice job on the trace work.

Great video. Loved your thought process and troubleshooting method. Great playing too, love P90's through a Marshall.

lil bud learning to talk i love it my new fav channel.

I was certain it was going to be that IC! Great video - bummer you had to swap all those caps and the two transistors. I think the owner of that amp should know it deserves a robust set of vintage tubes. Well done, man!

Dear Guitologist, I discovered yur channel some 6 months ago and really love the way you present and troubleshoot your projects. Having some electronics knowledge myself its very educational and already picked up lot of things I could use for my own modest repairs. Not being able to sent you stuff or make a donation which will significantly change your holiday destignation, which I think you deserve and would like to donate... I choose to express my thanks with..Standing in the Middle of the Street Naked Screaming "LONG LIVE THE GUITOLOGIST"! Not that I am trying to imply that you suck at what you do I wnder if you are aware of this other repair dude on KZread... Mr Carlsons Lab. He is something else.. I always go by the mantra..two always know more than one person. No matter how perfect I think I am, an other person with less knowledge than myself can always contribute something unknown to me. Anyways, thanks for your time entertaining and educating us..

I have a regular JCM800 combo...Single channel, no reverb. Best amp I've ever owned. Had it for over 20 yrs now. drooped in a Celestion Gold 50 watt speaker.....super nice. Recently had it thoroughly serviced...new caps, tubes, and sockets. Hoping to get another good 20 yrs out it. I think I will too. Solid amp

Excellent presentation and explanations , probably the best on line , thanks.

Nice work and playing, Wish i had a tech like you around here!

Nice playing there at the end my friend!!

Original JCM 800 FTW!!! Love those amps!

I bought this amp. Awesome that I can see the work that was done. The amp sounds great. I put a Classic Lead 80 in it. Also play it through a 1966b with 2 V30s

Thank you for sharing your time and knowledge with us.

My brain just exploded. I understand everything you're talking about. I have to do similar troubleshooting at work but we don't have to chase it down like this thank god.

Yes, love the adorable talking and happy sounds... Great snooping.. Great vid.

Great job bro. Dang you know ur stuff. I liked how thorough you were. I liked the fact that you took your time and went into great detail of what you were doing. im wondering if I have any probs. in the future with my amp if I could send it to you. Thanks Mitch

I have always played around with radio and amps. Not so much nowadays. I have been a Bass player since 1965. I enjoy your videos, thank you. Also your guitar playing and also have a Tele .By the By I gave up TV in 1991 .Keep on truck'in

Please make a video on making a signal tracing jig like the one you use. Great job on the channel and awesome videos! I love your sense of humor.

@dkblanke

5 жыл бұрын

I would like to see this too.

Watching this makes me glad that the JCM 800 I recently picked up is a much simpler design without all that switching crap, and no reverb (1983 4010 vertical input 50:watt 1x12 combo). It is also loaded with a G12M-65, rather than the 70 in the amp in this video. Mine also has 6550’s rather than EL-34’s. I did spend a bit on a full service to fix some issues (replaced tube sockets, new tubes, and replaced any drifted components). Good as new now.

I didn't see you put the negative feedback wire back on, but evidently you did. What a journey

that amp sounds amazing dude!.... great playing too man!

Great video, as always. Thanks

I used to have the vertical input 2x12 50w combo. man that thing was a beast and heavy.

Great video, explaining, and playing.

You are a living legend! You rock on electronics and on the guitar!

You made it well done, cheers for the video

I had a 82' jcm800 I clipped the clipping diodes out of circuit , made it into a vintage sounding Marshall. Amp builder Doug Bray told me how to do this and it was awesome . good luck

Awesome channel watched a lot of your videos in the last few months

Cool little amp! Hello from across the river a bit, in Corydon, IN.

@TheGuitologist

7 жыл бұрын

Hi neighbor!

Man, I hope I can bring you my Rivera R-100 for a tune up one of these days. These are great videos; I commend you for vindicating the "experience" of taking Physics II. Cheers from Cincinnati!

Glad I found this channel. This looks like fun! 👍

WOW..I did'nt know these type video's were out there...GREAT ... I always wanted to do this for a living...but I can just watch you & the way you explain everything almost makes me think I know what its all about... LOL😎 ..YOU'RE the whip dude... i have a marshal combo...2morro I'll get all #'s & such for you..its not working now..i want you to fix it..how much etc. AND I know that question cant be answered right off😌

Nice video. That guitar and amp sound great. Nice playing at the end.

I love learning about amps... I have Valvestate 80 by Marshall. I love it.

Sweet git at the end. Awesome sounding jr.

5:49 I was just thinking to myself when i saw the amp flipped "Now that's the penny pinching way of doing it." I just hate to see that too. In a well built amp there's just no need for it and it makes working around the pots a pain in the backside. Just discovered your videos! They are wonderful.

You'd be surprised how many people watch these videos all the way through just to see possible scenarios for fixing and troubleshooting amps.....there are a lot of amp builders out here.....I really like watching your channel because I have my own amp build.....my problem is it's a 1959 Marshall circuit and I can't make up my mind if I want 1959 or 2203 or a mod of some kind.....the 1959 is too loud so I tried a ppimv but couldn't get it to sound right when turned up a quarter of the way without it being piercing in the higher register....don't know if it was the tube effect loop of the treble wiper feeding the phase inverter or what...it did have send and return levels....I don't like slamming my phase inverter tube....I just couldn't get rid of the piercing highs....so I got rid of both....going to add a gain stage and a both Jose and 2203 master and be done with it I guess.....I read all your comment....I bet you didn't read mine.....lol

Great job!! its hard to find a good amp tech out here!!

We LOVE your videos! Just great.

Great video. Amp sounds cool.

Love the videos here keep ‘em coming

Awesome demo of the amp! it sounds killer

I like your videos, very educational!

The DI is "direct interface" for connection to a mixing console or power amp for larger venues. The 4210 is a great little amp, loud and versatile, killer crunch tone by turning the master all the way up, dial in gain as desired, but will wake up the neighbors.

@TheFRiNgEguitars

7 жыл бұрын

actually have not watched the vid yet.. the can caps on these Marshalls are extremely high quality and seldom need replacement.

Wow man! I am able to completely follow along here now. Incredible! I think it’s almost time for that AO project. I am going to try to add reverb from the ampeg reverberocket ! It’s a 12au7 one tube reverb. Just need to understand how to bias that tube and where to put the reverb circuit in the layout after the preamp

After all the investigating and the feeling of accomplishment .. i always love the 'pay-off jam' at the end ...

Back in the 70's when in electronics class first thing we would do is test all the tubes..nice vid..

Gotta love the guitar face at the end of the video. Keep on rockin.

Such an amazing amp!!

nice amp,reminds me of my jcm800 head and 1960a 4x12",used to carry that thing everywere,wish i was still that strong

I do love these videos Sir!

@TheGuitologist

7 жыл бұрын

Thanks for watching and taking time to comment.

Not sure where you live, but if you live in the UK, just book an appointment with the Marshall factory and they will sort it out. They also only charge costs, in fact last time I was there, they didn't charge me. I would never risk any of my amps with anyone but the Marshall Factory...man I love them.

Very cool! I love this channel!

@TheGuitologist

6 жыл бұрын

Thanks man. Glad to have ya.

Awesome vid. You should grab a few solid state preamp tubes. Great for checking amps to negate bad pre's because they are practically indestructible.

Great amp and cute little helper!

I have a 4210 on the bench which I had to replace the power switch (melted), replace PT, do a rectifier diode work around because the board was burnt up and all traces gone. Someone did work their which caused the rest of the damage. Amp up working but if you turn the reverb pot it blasts into oscillation. The work continues. Mark

always start with the tap and wiggle tests! lol. these are very amusing for me coming from electrical diagnosis failure