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Old 02-01-2013, 04:30 PM   #1
T00DEEPBLUE
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Question Are my valves dead?

So i was in the middle of playing my guitar, minding my own business and all of a sudden, my amp quickly fades out and hasn't made a single sound since.

I've tried multiple cables which i know all work, to no avail.
I've tried a couple of guitars that i know work, to no avail.

I've turned it off, left it a while, turned it back on, taken it off standby after letting the valves heat up for a minute and nothing happens. The only noise it's making is a quiet hum.

The amp is a modded Peavey 6505+ 112. The power valves are JJ's and i replaced them a few months ago. I haven't done a bias mod to the amp yet, the other mod i've done is the V30 speaker, but that's about it.

Does this mean that my power valves are dead? I've only replaced the valves a few months ago and it's been running fine ever since i replaced them. The valves are glowing normally.

This really sucks. I just want to enjoy playing my guitar and now i can't.

Edit: ****ing wrong thread.

Can a mod move this thread to GG&A please?
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Old 02-01-2013, 05:54 PM   #2
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Another thing i've noticed is that when i hit the amp, the spring reverb comes through the speakers as it should, but i have no guitar signal.
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Old 02-01-2013, 06:45 PM   #3
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Quote:
Originally Posted by T00DEEPBLUE
Another thing i've noticed is that when i hit the amp, the spring reverb comes through the speakers as it should, but i have no guitar signal.


So its not the power amp bit then. Could be a pre-amp valve. Swap V1 ad V2 for V3 and V4. My guess is that its V1.

Diagram:

http://www.prowessamplifiers.com/sc...cs_and_BOM.html
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Old 02-01-2013, 08:33 PM   #4
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Thank you for the input. No pun intended.

Could it just be simple like a loose connection?
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Old 02-01-2013, 09:00 PM   #5
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It's probably a preamp tube. Swap an extra 12AX7 into each position in the amp and see if one of them is blown.

If that's the case, I would just re-tube the entire preamp if I were you, unless you've already re-tubed it. I would recommend JJ ECC83S tubes in everything except the Phase Inverter, where I would put a JAN Phillips 5751 in.

Not only will it likely take care of your problem, but it will also improve the sound of your amp a good bit. If you had the head instead of the combo, I would recommend a JJ ECC803 for V1, but those have a tendency to go microphonic in combos.
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Old 02-01-2013, 09:07 PM   #6
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Sounds like a preamp possibly. Order new ones and switch them 1 at a time until you find the dead one. Through it way... keep the rest as spares.
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Old 02-03-2013, 07:55 PM   #7
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Bump.

I've pulled all the preamp valves and had a look at them.

4 of them are the standard Ruby 12AX7A's while the 5th is an Electro-Harmonix 12AX7EH. What would you guys recommend i use? Or should i just order the same brand and model?
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Old 02-03-2013, 08:07 PM   #8
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Switch the order of them and see if you have a change. Try it on all channels.

Also- plug your guitar into the fx return and see if you hear it.

JJs are always a good value. They sounded better the EH to me. Rubys are rebranded.
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Old 02-03-2013, 08:17 PM   #9
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Does the 12AX7EH have to be in the slot i removed it from and does it have to be a 12AX7EH?
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Old 02-03-2013, 08:56 PM   #10
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Originally Posted by T00DEEPBLUE
Does the 12AX7EH have to be in the slot i removed it from and does it have to be a 12AX7EH?


The EH is just the manufacturer name initials. It's not a different designation. Swap away...
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Old 02-03-2013, 09:10 PM   #11
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Have you pluged your guitar into the FXloop retun ? Do this and see if you have sound comming from the speakers if not itis the power-amp. If you get sound then the preamp is to blame.

I agree with everyone, it most likely is the pre-amp, but just check real quick
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Old 02-03-2013, 09:26 PM   #12
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Quote:
Originally Posted by R45VT
The EH is just the manufacturer name initials. It's not a different designation. Swap away...

Thanks for the help.
Quote:
Originally Posted by Robbgnarly
Have you pluged your guitar into the FXloop retun ? Do this and see if you have sound comming from the speakers if not itis the power-amp. If you get sound then the preamp is to blame.

I agree with everyone, it most likely is the pre-amp, but just check real quick

I'm pretty sure it's the preamp because when i hit the amp, the reverb springs do go off and ring out through the speakers. As the reverb unit is running through the effects loop (i think) then i think the power section is fine.
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Old 02-03-2013, 09:31 PM   #13
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Originally Posted by T00DEEPBLUE
Thanks for the help.

I'm pretty sure it's the preamp because when i hit the amp, the reverb springs do go off and ring out through the speakers. As the reverb unit is running through the effects loop (i think) then i think the power section is fine.


Try it anyway. Takes 5 seconds.

Next swap the tubes positions.
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Old 02-03-2013, 09:47 PM   #14
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Quote:
Originally Posted by R45VT
Try it anyway. Takes 5 seconds.

Next swap the tubes positions.

Yeah I read all of TS post so I didn't look like a ****** this time
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Old 02-03-2013, 09:53 PM   #15
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Quote:
Originally Posted by Robbgnarly
Yeah I read all of TS post so I didn't look like a ****** this time


buddy I knew you missed it on the last one. Too many paragraphs.
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Old 02-06-2013, 08:39 PM   #16
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Bump:

The amp's been fixed, but getting it repaired was quite a journey.

Not only had one of the tubes died, but also, 4 of them stopped lighting. It turned out that one of the bridge rectifiers overheated and burned out. I've replaced the diodes, resoldered them, put the new valves in and the amp is running fine.
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