Dating a DSL JCM 2000

[Backwoods Joe]

Got a JCM 2000 on the bench that has a terrible hum & is noisy. Is there a way to date it by the SER. No.?
THX, joe

[bnwitt]

What model is it?

[BnATX]

Not sure if they are all the same but mine had a sticker on back with the serial number and the date is in that.
Mine was like M-2004- xxxxxx So the year was 2004.

[Backwoods Joe]

THX BnATX, I found it. It's a 1998 model & i'm thinking it probably could use a cap job. joe

[phsyconoodler]

Doubtful it needs caps.
Those amps are prone to lots of other problems.You need to be very good at diagnosis to repair those successfully.
Hum problems can be a number of things,like power tube issues,bias,burnt screen resistors,lifted PCB traces,etc,etc.
  Caps would be the very last thing and likely not even enter my mind.

[Backwoods Joe]

phsyconoodler, Thanks for your input. I've already checked the usuall stuff. I cranked the amp up this morning to show a friend how bad the hum and roar was...... and it was gone! so i guess i'll watch it some more. One of my main concerns besides the hum was the way everything sounded slightly out of tune. strange

[phsyconoodler]

Does your 'usual stuff' include trying new power tubes,preamp tubes and checking the bias?Also remember that the bias checking pins measure for two tubes at once.

[Backwoods Joe]

Yea I tried all that, even some new output tubes. My son's playing it now, sounds fine. Same guitar, cord everything.

[Ritchie200]

Hey Joe,
Does anything change when you leave it on - for a long period of time?

Psyco is right in that this amp is possessed with many issues, the majority being thermally related.  Check out this site for details:

http://www.lynx.bc.ca/~jc/TSL122.html

I had two of these dropped off in my lap with the same issues and was scratching my .... for a long time - before finding this site and figuring out what was happening.

Good luck!
Jim

[Backwoods Joe]

Ritchie, When i first turned the amp on it had issues. We'd played for 15 minutes or so, a few times untill yesterday when it was fine. Thanks for the info, I'll check it out. Now i see why these amps sell for so little used.

[bnwitt]

So I'm still wondering whats model it is.  100 watt, 50 watt, 40 watt, 20 watt?  If it's a hundred watter you could have a C46 issue.

[BnATX]

I had the 100 watter but i never had any trouble with C46. Most people just cut it out or replace it with a 1Kv cap.
I did have a slight problem with the bias drift cause of  the heat. I thought mine being a later model was not supposed to have that issue.
Or so i read.  
I would let mine sit for 30min. or so and get good and hot and then set the bias. Seemed to then be stable. Never got around to actually doing something about that but i did change stuff in the preamp. I did not like the way it sounded. Too fizzy and whatnot for my tastes. Got it sounding pretty good, i thought.
But i got tired of dealing with all the wires and pcb's to make any changes, so i put it all back to stock and sold it.

[Backwoods Joe]

Sorry bnwitt, it's the 50.