Build Your Own Clone Message Board

Alright, so my brother's Classic 50 212 has been out of commission for a long, long time now and over the coming months, I intend to resurrect it.

All I know is that there are "serious issues" but no one can remember what they are specifically. A couple of pots seem FUBAR, but that's a relatively minor issue. The tubes were pulled at some point (and are now long gone), so I'm going to have to troubleshoot this from square one.

I've found a service schematic, I know I need to build a cap dissipation tool and a current limiter.

So, anyone have any suggestions of what to do and where to start? Thoughts on a good set of replacement tubes? Modifications or improvements I should make as long as I'm balls deep in this thing anyway? Tips or tricks?

Gonna take my time with this one so no worries that I'll go diving in there with both hands looking for a B+.

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Bikers have more fun that people do.

Free "open source" EagleCAD files: 99ZuluFX

No advice/suggestions, just wishing you luck! Those Classics are some of the best amps out there when they’re working. I’m sure Morgan, Scooter and others have repaired their fair share of them so you should be able to get some good input from the forum.

I have a Classic 50 4x10. I think I got it at a pawn shop for couple hundred bucks and TBH, it's one of my favorite amps. And I haven't even done anything to it...not even upgrade the speakers. Still has the original tubes.

Anyhow, I'd start by taking some voltage readings without the tubes in. The schematic doesn't say what screen, B+ and B++ should be, but I'm guessing it's somewhere around 400V, 350V, and 325V since their respective power filter caps are rated 500V, 450V, and 450V.

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*patience is a virtue*

Please do not PM me. email is prefered. keith@buildyourownclone.com

My approach to amps like this is get a set of known working tubes together for it. Put the amp on the limiter with no tubes installed and see if there any shorts. If no shorts, plug in the preamp tubes and do the same thing. If still no shorts, then plug in the power tubes and do it again. If you are working on a light bulb current limiter, the light bulb will glow brightly as the caps charge when you've got the power tubes installed, then back off a bit, but will stay lit. If you have a short at that point, the bulb will glow very brightly. If you have a normal current load, it will glow dimly. You can tell the difference. If the amp seems to be drawing a normal current load, you can take it off the limiter and bias up the power tubes (you can't bias them correctly on the limiter because the B+ voltage will be much lower). If the sound is all jacked up at that point, you can then start troubleshooting the signal path.

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MasterDelayer/Reverbrador/Ampaholic/TopJacker

Keeping a close eye on this thread!! While I have successfully built a number of amps, I've never (yet) had to repair a non-functional one. So these tips & techniques are of great interest to me, because I'm quite sure that SOMEDAY I'll need to use them.

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“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2

Dlab on youtube has done repairs on those amps. He's also usually very generous with schematics and advice. He may be able to help with a schematic and voltages.

Here's one of his videos, fixing a dead Classic 30:

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“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2

This is excellent stuff, y'all. Thanks!

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Bikers have more fun that people do.

Free "open source" EagleCAD files: 99ZuluFX

Pain in the ass working on those PCB's. Careful with the traces. Check for burns. I'm working on an AC15C1 now that got left on all night. Daughter board with 2 x 9pin sockets for EL84's got all burnt at the solder connections to the pins. Arc'ing occurred. BTW, I bought a used Classic 50 2 x 12 for 300.00 and gigged with it for 5 years. GREAT sounding production amp. At least the cleans are. Good luck.

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Everyone likes sausage. Nobody wants to see how it's made.

I had a 1x15 Delta Blues for a while that was a great sounding clean amp, as well. Thunderous lows with that 15" speaker. Was too loud for me at the time, though. Kinda wish I still had it now....

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“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2