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NickS · Last edited by NickS on Fri Sep 24, 2010 11:49 am; edited 1 time in total

So it started intermittently dropping volume and I thought I'd better take a look.

1: Phase inverter ECC83 socket is misshapen.
2: So is the final preamp ECC83 socket, though not so bad.

This means I need to get some ceramic B9A sockets and improve the cooling. Bum.

NickS · Posted: Thu Sep 23, 2010 10:32 pm Post subject:

Ceramic sockets arrived today so I put them in tonight, yell if you want pics.

Bacchus · Posted: Thu Sep 23, 2010 10:45 pm Post subject:

Pics of work being done on an amp are always a good thing.
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Mike · Posted: Fri Sep 24, 2010 8:48 am Post subject:

+1

Good luck with the PCB!

NickS · Posted: Fri Sep 24, 2010 11:48 am Post subject:

I imagine the valve orientation, with a grille to let heated air into the chassis, and proximity to the dropper resistors will also shorten the life of the smoothing caps:

Inside shots: a few wires need to be unsoldered before you can free up the main board.

Board freed:

Here's the damage to the valve bases:

As you can see, the pins on the new ceramic bases were wider than the old plastic ones so I had to cut them down to size:

<edit: moved images from Photobucket>
First one in:

The ceramic bases are also taller than the plastic ones, but that's not a problem in this case because the EL34 sockets are so tall that the ECC83 sockets are well below the surface of the chassis.

Doog · Posted: Fri Sep 24, 2010 12:11 pm Post subject:

Scary stuff, is it aliiiive yet?
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andrew floss musics

NickS · Posted: Fri Sep 24, 2010 12:21 pm Post subject:

Mike · Posted: Fri Sep 24, 2010 12:42 pm Post subject:

Nice work!

NickS · Posted: Fri Sep 24, 2010 8:58 pm Post subject:

Thanks. It hasn't fixed the general up-and-down-ness of the volume, and all the solder joints looked fine on the main board, so I guess I'll get some new valves. The guy didn't play much but these look like the original set from 1997. Shocked

Sloan · Sexy Predator Joined: 20 Apr 2006 Posts: 11797

I've already worked on two JTM60's this year, those two blue filter caps, i'm surprised those are still ok. These amps are an ass pain to dick with because the way they are put together. The fucking components get hot from the tubes, such bullshit.

NickS · Posted: Thu Sep 30, 2010 9:10 pm Post subject:

Hmm, looks like the cause of the intermittent volume drop could be the serial effects loop jack sockets (this has been mentioned elsewhere as a possible cause). Played rehearsal (2.5 hrs) last night with the loop jumpered, no problem. Without the jumper, it started playing up again after a few minutes tonight. Jumpered again - fine.

Also - must fit the fan mod. (But they are a bit awkward to work on.)

Sloan · Sexy Predator Joined: 20 Apr 2006 Posts: 11797

NickD · Posted: Tue Oct 05, 2010 9:16 pm Post subject:

Interesting to see, I know there are a lot of issues with JTM60s, but mine has been fine - I bought it NOS in '06, and it doesn't see heavy use.

NickS · Posted: Mon Sep 12, 2016 1:20 pm Post subject:

So I've been using it for six years with a jumper on the effects loop and I see someone has got a fix for this problem on eBay:

Hidden:

Doog · Posted: Mon Sep 12, 2016 1:27 pm Post subject: