Thanks Mark!

I shall get a copy!

Nice...........IS that book still in print ? And, who sells it ? Thank you............

Thanks! I really appreciate those comments.

@skmann22, which other channels do you find interesting? I watch Uncle Doug, D-Lab, and just happily found Stuart here.

@@stevelark9840 Yes Uncle Doug of course, he got me started with the idea of videoing my repairs. The Guitarologist is also pretty good. Also Psinoc Audio are great and very knowledgeable. There's also a woman (cab;t recall her name) who is a bit of a beginner but is doing good work out there her channel is Fazio Electric. I also enjoy Fran Blanche of 'FranLab'.

Thanks very much!

That's the wonderfui thing about KZfaq - so many people willing to share their knowledge. I was locked out of my Prius last week (totally flat battery). A KZfaq vid showed me how to get in.

Thanks Zack!

Thanks that's exactly what I am trying to achieve. So easy to edit it to make you look like a miracle worker!

Ha ha! Yes I watch all sorts of stuff on KZfaq too. It's amazing what people get up to!

Thanks! I'm pleased you are enjoying it.

Many thanks.

I've forgotten already! :)

You need to get out more! Seriously though, thanks for the thumbs up.

Thanks Ken!

Yes we are a breed!

Glad you liked it!

Cheers Monty!

Cheers Daz much appreciated!

Glad you enjoyed it thanks for subscribing.

Thanks Frank. NAsty problem you had there!

Yes I like to keep the struggle in the video if possible. All too easy to make yourself look like a brilliant fault finder. What you say about confirmation bias is SO true.I have stories....

Hi I'm pleased you are enjoying them! Yes I'm quite careful. 400V DC is no fun - but was talking to a friend yestrday who regulaarly worked on 33Kv (!) equipment. Yowza!

Glad you enjoyed it Mike.

Thanks for the feedback Ed.

Thanks Michael!

Many thanks glad you enjoyed it!

@@stuartukguitarampguy5830 No problem, it’s building up my understanding of how tube amps work 🤙

Cheers Pat

Hi. Great news on your getting into the amp repair business. Watch as many KZfaq videos as you can as you can learn a lot that way. On you amp that's a tricky one. If you're going to start repairing amps you'll need to get yourself soe way of measuring the actual power the amp is giving. I do that with a dummy 8ohm load and I hook the scope across that. You can then work out the power (if you don't know how ti do that jut ask me). You're going toi need to start getting some test equipment together so a scope and a signal generatot are essential I'm afraid.

Good tip thanks.

Let's hope so!

Was it the C11 after all? Fairly certain I have the same problem and C11 getting no reading.

Hi Happy to help of course but it's not easy doing these things at a distance. If you go the very end of any of my videos you'll see a splash screen with a contact email on it. Contact me via that.

Agreed. There's also a quick mod you can do to ake sure it's on the 240V tap not the 230V. This brng down all the voltages by about 5%.

Aww, shucks!

Hi David I'm dying to know what was actually wrong with it!

@@stuartukguitarampguy5830 just found your channel a week or two ago.. love your content and your detail.. First Rate! wish I knew what really had been the problem with that JCM900.. though a bit to much gain for my taste. traded it and some $$/££ for a fender deluxe reissue.. which thankfully I adore played clean along with well worn AC30...

Hi James I can;t reall help I'm afraid. It's beeen 3 years since I did this! I hope you manage to get it sorted.

Hi it was C11 which is 2200pF at 1KV or greater. Good luck

Hi Rick Sorry but the network you mentioned doesn;t ring any bells. I've not had any issues with EL84 screens, but other may have?

I've heard it called the conjuntive filter. It is in the RCA tube manual, but the actual name escapes me at the moment. If I come across it, I will let you know. Cheers

@@kengevers8738 Right, its called a Zobel network.

Thanks Rick. 😊

Yes they are always best but it's all down to money of course. PCBs are used to save a LOT of cost and hence make the amp cheaper to buy.

good-un Yes probably to eliminate parasitic high freq, oscillation. Stuart, I love Your channel, and You give excellent advice, and analysis in these videos. When i test amps, I always attach the output to a speaker with a 'scope across the speaker, and use a Variac to bring the supply voltage up step by step, starting at about half voltage. Most tube amps work fine under these conditions with about 1/4 output, so there is a much lower risk of burning things, further. On viewing the video of this amp, I suspected something in the output section or phase inverter. So then it is easy to look at the waveforms at both places and see where the clipping occurs. You don't have to make theories, or hypotheses, with a little more testing, and observation, that tells You exactly where the problem is. Divide and conquer is the name of the game. You can always insert a signal at the phase inverter, and see if the thing works perfectly before that point or after! You tend to always mention HT 1st which is great... serious problems from the power supply should be eliminated 1st,... for Your American viewers, HT means what we call B+ or the initial High Voltage Supply. (High Tension) If I had seen this schematic, I would have immediately removed C 10 and C 11 as they are unnecessary, and elements of poor design. As Tom Colangelo chief designer at Mark Levenson Amps explained to me long ago, an amplifier with two 90 degree phase shifts in a negative feedback loop, always run the risk of creating oscillation, at the given frequency where 180 degrees total of phase shift occur, (as 180 degrees is already produced by the amp). This is in fact exactly what a phase shift sine oscillator is! Actually stray capacitance can easily introduce another 90 with the parasitic capacitance in parallel with the signal. These caps are intended to suppress hi frequency oscillation, but instead can easily CAUSE it. Good design, seen in for instance, the Fender AB 763 circuits, or the 5f6 bassman, do not use such caps. It is always better to remove the parasitic capacitance in preamp or tone circuits or introduced by bad grounding schemes in the output, than adding more BS, to a clean circuit hoping to eliminate High Freq Osc. If You are monitoring the output with a 'scope You can immediately see when hi freq oscillation occurs, and then go about snubbing it out with one cap, and a resistor in series to ground in a part of the circuit without a feedback loop! Any amp can be safely returned to a common sense design that more closely resembles an AB 763, which is pretty close to all the designs out there anyway! I am guessing that C 11 shorted because it is a small cheap ceramic cap and was probably seeing parasitic oscillation, which ran to almost full output.

Budget. Customer didn;t want to replace. Not gig critical.

High tension and is a term used for the high voltage.