Author Topic: The diagnosis is back about my blown JTM60 combo (Read 5090 times)

Brow · « **on:** November 18, 2005, 11:15:28 PM »

Hey guys.

I spoke to the tech today who has my JTM60 combo since it stopped working, and he's told me what's up with it.

It needs 2 new EL34 Power valves and a new output transformer

From what I gather this is a pretty serious problem, but the tech has told me that a new power transformer will fix the problem and maybe even improve the sound of the amp.

Just thought I'd make a follow up post to the 1 about my amp dying in the 1st place

Craig

big steve · « **Reply #1 on:** November 18, 2005, 11:25:45 PM »

yeah, apparently most if not all makers cheap out on the output transformers.

tewboss · « **Reply #2 on:** November 19, 2005, 12:46:08 AM »

My friend's silverface bassman 50 head had blown power valves and a blown transformer. The guy who repaired mine even coverted it to blackface circuit specs all in for 100 pound, so I wouldn't have thought it would have been too bad for you.

Brow · « **Reply #3 on:** November 19, 2005, 10:35:10 AM »

Thanx for the posts :)

Depending how the amp sounds when I get it back, I may sell it and move on. I'll see how it goes though :)

Craig

Ratrod · « **Reply #4 on:** November 19, 2005, 11:54:34 AM »

I had the same problem. It was an expensive operation. The Vanderveen designed Amplimo transformers are pretty good.

PhilKing · « **Reply #5 on:** November 19, 2005, 01:41:55 PM »

Quote from: Brow

Thanx for the posts :)

Depending how the amp sounds when I get it back, I may sell it and move on. I'll see how it goes though :)

Craig

Hi Craig, sorry to hear about the amp. It should be a lot better depending on which EL34's you put in and how good an output transformer. These are the cheaper transformers though. Check on Watford valves site and talk to your tech, I heard good things about TAD 34's and I like the Groove Tube Mullards. Ben swears by 6CA7's and if you are changing the output transformer you could Zakk Wylde it and go to 6550's!

Brow · « **Reply #6 on:** November 19, 2005, 03:48:13 PM »

Thanx for the posts guys :)

Quote from: PhilKing

Hi Craig, sorry to hear about the amp. It should be a lot better depending on which EL34's you put in and how good an output transformer. These are the cheaper transformers though. Check on Watford valves site and talk to your tech, I heard good things about TAD 34's and I like the Groove Tube Mullards. Ben swears by 6CA7's and if you are changing the output transformer you could Zakk Wylde it and go to 6550's!

I've been told that the parts needed for my amp are already on order, so hopefully they've bought some quality parts!

They've gone to Marshall for the Power Transformer as fara s I know, and probably the same for the valves.

When the amp's working, I'm happy with it. So I'll keep it as EL34's. Thanx for the suggestion tho :D

HJM · « **Reply #7 on:** November 19, 2005, 05:38:58 PM »

Any suggestion why it went?

Brow · « **Reply #8 on:** November 20, 2005, 12:20:22 AM »

Quote from: HJM

Any suggestion why it went?

These amps are notorious for problems as regards heat, because the valves are mounted horizontally across the chassis and the heat just goes straight up into the circuit board.

The tech thinks it went because the amp might've been running on only 1 EL34 for a while, which may've caused the damage to the output transformer.

I'm not sure this is true though, as I remember looking in the back of the amp and seeing both power valves glowing.

I'm a bit of a dumb dumb when it comes to the inner workings of amps though, so what do I know :D

tewboss · « **Reply #9 on:** November 20, 2005, 07:07:29 PM »

JJ Tubes get pretty decent reviews in the US which are distributed through Eurotubes over there. I've got TAD (Tube Amp Doctor) valves in my Marshall which sound awesome. The thing that puts me off Groove Tubes is that reading their literature you would think they designed the tubes themselves rather than simplay source them and rebadging them. TAD actually are involved in the design stage so do actually get involved in the R&D stage rather than just purchasing them.

If you haven't already had it repaired, try a guy called Trev Ridney in Walsall who does Tipton amps http://www.tipton-amps.co.uk. He was the guy who repaired my friend's bassman. He uses TAD valves in his amps as well.

Brow · « **Reply #10 on:** November 20, 2005, 11:15:33 PM »

Quote from: tewboss

JJ Tubes get pretty decent reviews in the US which are distributed through Eurotubes over there. I've got TAD (Tube Amp Doctor) valves in my Marshall which sound awesome. The thing that puts me off Groove Tubes is that reading their literature you would think they designed the tubes themselves rather than simplay source them and rebadging them. TAD actually are involved in the design stage so do actually get involved in the R&D stage rather than just purchasing them.

If you haven't already had it repaired, try a guy called Trev Ridney in Walsall who does Tipton amps http://www.tipton-amps.co.uk. He was the guy who repaired my friend's bassman. He uses TAD valves in his amps as well.

Thanx for the post :)

JJ valves were what I would've bought myself, but the tech already went ahead and bought a Mains Transformer and Valves from Marshall, so the JJ's will have to wait a while :?

When the time comes to re-valve my Orange AD30, I'm almost certain I'm using JJ valves in that :)