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DarrinPA
Silver Member
USA
221 Posts |
 Posted - 05/05/2008 : 21:25:02
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My friend has a tube amp head [Peavey] that sounds good but after 15-30 minutes it stops working. I've never repaired a tube amp head so I wouldn't know where to begin. Does anybody have any ideas of what could be the problem?
I'm sorry if this is very vague but I don't know much about it. Maybe tell me what I should look for when it shuts itself off? |
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pedals 4 pv
Platinum Member
Canada
1351 Posts |
Posted - 05/05/2008 : 21:36:56
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Peavey schematics and many others available free, here:
http://blueguitar.org/schems.htm#Peavey
Good luck with the repair project |
Edited by - pedals 4 pv on 05/05/2008 21:39:51 |
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bossFan
Bronze Member
Portugal
97 Posts |
Posted - 05/05/2008 : 21:38:08
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Check the speakers and they connections.
Watch closely to the tubes heaters. They must be on (The tubes must have some yelow light inside).If they have that kind of light, you must check for the tube plate voltages(BE VERY CAREFULL - It�s high voltage around 300V and up)
Good luck |
Edited by - bossFan on 05/05/2008 21:44:52 |
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jack
Platinum Member
USA
1418 Posts |
Posted - 05/06/2008 : 01:25:05
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quote:
Originally posted by DarrinPA
My friend has a tube amp head [Peavey] that sounds good but after 15-30 minutes it stops working. I've never repaired a tube amp head so I wouldn't know where to begin. Does anybody have any ideas of what could be the problem?
I'm sorry if this is very vague but I don't know much about it. Maybe tell me what I should look for when it shuts itself off?
When was the last time the amp, or has the amp ever, had the tubes changed? Just wondering, as I would try messing around with the tubes before getting ass-deep in capacitors, resistors, transformers, etc.... |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 05/06/2008 : 02:21:21
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quote:
Originally posted by DarrinPA
after 15-30 minutes it stops working
I'm thinking this HAS to be related to temperature. 30 minutes is about the right time for everything to heat all the way up and stabilise.
Is the signal completely gone when it goes, or is it just diminished?
Tube amps are essentially simple beasts. Input tubes, power tubes and output transformer. I wonder if this particular model has a thermal cut-out on the mains transformer? Hmmm... if you leave it plugged in, does it come back on later?
Can you find out the exact model and maybe take some pics of the inside of the amp?
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Edited by - Laurie on 05/06/2008 02:22:28 |
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DarrinPA
Silver Member
USA
221 Posts |
Posted - 05/06/2008 : 03:22:00
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Wow, already alot of good info and questions.
P4P, thanks for the link.
BossFan, the head has been tested on a few different cabs with different speaker cables, but I thank you for thinking of the simple things first. I don't how to test the tube plate's voltage, I'm hoping I can try MORE simple things first.
Jack, I'm guessing the tubes haven't been changed in 10 years and I like your way of thinking.
Laurie, The signal is sometimes gone completly and sometimes stays just barely there. Would that be a power-tube problem or pre-amp tube problem? I don't have the amp head at my house but I'll ask about the time it takes to start working again and for pics. |
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pedals 4 pv
Platinum Member
Canada
1351 Posts |
Posted - 05/06/2008 : 04:28:36
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| You may be able to find someone with a tube tester, in your area. That would be the easiest way to find a bad tube. |
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jack
Platinum Member
USA
1418 Posts |
Posted - 05/06/2008 : 06:54:27
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quote:
Originally posted by DarrinPA
Jack, I'm guessing the tubes haven't been changed in 10 years and I like your way of thinking.
Yeah, I say start looking at simple stuff first. If I have a headache, I'd take some headache medicine, and if that doesn't work, then I'd go to doctor. Its a tube amp, try new tubes and see if that has any effect, or as Laurie suggested, test the tubes to see if they are the culprit. Sometimes when troubleshooting, its sometimes easier to eliminate what works in order to figure out what isn't. Also, if you haven't messed around with amps too much, please be careful as there can be some high voltages stored up in capacitors and other things even after the amp has been unplugged for awhile... |
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Goran
Double Platinum Member
Sweden
2203 Posts |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 05/06/2008 : 16:48:10
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Hi DarrinPA & Guys
Don't forget the simple things, like looking for dry joints & bad connections.
Especially around the resistors & other big fat things that get HOT.
Could also me old power supply caps, that have gone leaky & high in ESR.
Be VERY CAREFUL a lot of these caps can hold a lethal charge for a long time.
But I would do a close inspection, in good light or daylight, after it has been off for a quite while.
Unless you know how to safely discharge the power supply caps.
If you're not sure of an area, component, or solder joint, take some pics & post them here to the forum, to see if we can help.
Regards Dr. Bob |
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Topic |
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Tube Amp Repair
