Jump to content
aberdeen-music
Sign in to follow this  
TR!ΔNGL€ T€€TH

Valve amplifier assistance

Recommended Posts

I am having problems with my Marshall JTM 60 3x10, namely that it is not producing any sound. This problem first appeared whilst I was soundchecking for a gig, so the amp was on and there wasn't any spectacular explosions or anything, just no sound when I turned the standby off.

I've checked the obvious things, the speaker cable is fine, the amp is coming on and the mains fuse is okay. There is no sound at all coming from the speakers, but I can hear the amp switching between channels. The valves are lighting up, but I suspect that they are the problem. There are four ECC83's in the preamp stage and two EL34's in the power amp stage.

I am thinking that my best bet would be to take it into R'n'B or Bruce Millers and have an expert look at it, but I thought I would post and see if anyone had any ideas? Especially any way of narrowing down what the problem is.

Share this post


Link to post
Share on other sites

Might be the power amp valves. If it was the preamps, you'd get at least a bit of microphonic feedback. If you can hear the channels changing, then that may possibly rule out the chance of it being the dreaded output transformer too. But I don't even know what I'm basing that on.

Share this post


Link to post
Share on other sites

It needs to go to the shop. Unless something is loose, no sound is a blown output tranny or something else. Not likely to be power tubes unless you're blowing fuses. Are you sure the speakers are ok? And the speak wire is fine?

Share this post


Link to post
Share on other sites

Could be internal fuses if that amp model has any. Had the same issue before with amps, some fuses can blow on the circuit board but the amp will still power up but have no sound. If it is that they are easily replaced and can maybe just signal a faulty power tube

Share this post


Link to post
Share on other sites

My HT fuse kept blowing in my dsl 100 resulting in no sound coming from the amp.

Turns out a dodgy cab at cpt toms resulted in my transistor blowing and knocking out 2 valves at the same time.

Took it to Kennys music in Dundee - sent it to Marshall free of charge and fixing it for free because its still under warranty.

Share this post


Link to post
Share on other sites

R&B don't charge anything to look at your amp.

If need be, it'd get sent back to Marshall to get checked out. If it's a combo it's 40 to put to them (25 for a head) (this is when out of warranty) and they will assess it and then get in contact before doing any work.

R&B could change the valves and see if that was what the problem was without needing to send it away. Maybe a wise idea as a first port of call if they haven't been changed in a long time and it's been used a lot.

:)

Share this post


Link to post
Share on other sites
R&B don't charge anything to look at your amp.

If need be, it'd get sent back to Marshall to get checked out. If it's a combo it's 40 to put to them (25 for a head) (this is when out of warranty) and they will assess it and then get in contact before doing any work.

R&B could change the valves and see if that was what the problem was without needing to send it away. Maybe a wise idea as a first port of call if they haven't been changed in a long time and it's been used a lot.

:)

Well I changed my valves a month ago because of this crackling noise that was happening, I don't know much about valve amps and presumed that'd be the issue due to naivety. But this crackling happens even when there's nothing going through the amp, there doesn't even have to b ea lead plugged in. The amp still sounds good and you can't really hear it when you're playing. but it's a pain in the arse on stage between songs. I think it's probably the electrics, is there anybody in town who could fix this?

Share this post


Link to post
Share on other sites
Well I changed my valves a month ago because of this crackling noise that was happening, I don't know much about valve amps and presumed that'd be the issue due to naivety. But this crackling happens even when there's nothing going through the amp, there doesn't even have to b ea lead plugged in. The amp still sounds good and you can't really hear it when you're playing. but it's a pain in the arse on stage between songs. I think it's probably the electrics, is there anybody in town who could fix this?

Do you have an effects loop in your amp? If you do can you plug a short patch cable into the send and the other end to the return, then try again and see if the problem clears?

Share this post


Link to post
Share on other sites
R&B don't charge anything to look at your amp.

If need be, it'd get sent back to Marshall to get checked out. If it's a combo it's 40 to put to them (25 for a head) (this is when out of warranty) and they will assess it and then get in contact before doing any work.

R&B could change the valves and see if that was what the problem was without needing to send it away. Maybe a wise idea as a first port of call if they haven't been changed in a long time and it's been used a lot.

:)

Cool, cheers for replying. I think that I'll be taking it down once I get a hand with transport. I assume that I'm best calling in advance, rather than just appearing with my faulty amp?

Share this post


Link to post
Share on other sites
Cool, cheers for replying. I think that I'll be taking it down once I get a hand with transport. I assume that I'm best calling in advance, rather than just appearing with my faulty amp?

Consider this thread your call in advance - I'll let the others know that you'll be down at some point :up:

Share this post


Link to post
Share on other sites
Do you have an effects loop in your amp? If you do can you plug a short patch cable into the send and the other end to the return, then try again and see if the problem clears?

BOOM and it's fixed! nice one! anyone want to buy it? haha

Share this post


Link to post
Share on other sites
BOOM and it's fixed! nice one! anyone want to buy it? haha

Seen this problem on a few amps and took me a while to figure out what was going on. Its just the effects loop jacks building up dust or dirt and giving a bad connection and this cuts out sound at times or gives noise and crackle. When you put a cable between them it solves the connection break. You are best opening the amp and gently rubbing the metal parts of the jacks with a flat head screwdriver and cloth. Don't use electrical solvent cleaner unless your confident you won't get any on the circuits. That stuff is good but can corrode circuit boards and stuff if it gets near

Share this post


Link to post
Share on other sites
best guy to see is dennis marshall in dunfermline

dennis marshall

forget brucies or r&b. quite often depending on the job he'll do it while you wait

Ah! wide words from Triggs the Fender Blaster Master. That bloody Fender he did is awesome:up:

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  

×
×
  • Create New...