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Author Topic: sound problems with Peavey Classic 50  (Read 8389 times)

awdman

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sound problems with Peavey Classic 50
« on: November 15, 2009, 03:25:52 PM »
Hi all,

I am working on a Peavey Classic 50 and it has some issues that I need help with. It plays loud and plays good but when it is idleing it makes noise that I wish it would not. I have changed all of the tubes. The orginal problem was on of the power tubes burnt out causing a trace to burn up, I replaced it and got the power back. I am having a problem with random sounds (see clips) they vary in strength the first clip and second clips were recorded 5 minutes apart. If I turn the volume up it gets louder and lis louder if I switch to the lead channel. The Classic 50 has a effects bypass which bypass the controls, If I do that it goes away.  Does this sound like a bad connection, ground, or something elese.  ***turn volume down on clip one***

Thanks,
Anthony

Brymus

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Re: sound problems with Peavey Classic 50
« Reply #1 on: November 15, 2009, 07:06:42 PM »
That is strange I have a tube amp that makes that exact same noise when you unplug the cord from the input.
It only lasts for a few seconds and only when you unplug from the input jack.
I have checked several times and cant find anything wrong no bad connections or voltages outa whack.
I hope someone else might know what your problem is,so as to help with my similiar issue.

phatt

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Re: sound problems with Peavey Classic 50
« Reply #2 on: November 16, 2009, 04:00:22 AM »
You say it gets louder if you turn the volume up,,, then my guess,, The problem is *Before* the volume control.
Possible fixes,
dirty/ loose/ worn valve sockets. gently nudge the preamp valves see if it goes away.
Dirty terminals on switching mechanisiums on input sockets and EFX in out sockets.
Dirty or worn tracks on one or more pots.
Bad solder joins.
an interstage cap going futt.

What really Does concern me is you've made mention that the power tubes destroyed themselves :o. just replacing the burnt track won't fix that.
Sounds like the whole amp needs to be looked at.
Phil.

awdman

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Re: sound problems with Peavey Classic 50
« Reply #3 on: November 16, 2009, 06:54:35 PM »
What really Does concern me is you've made mention that the power tubes destroyed themselves :o. just replacing the burnt track won't fix that.
Sounds like the whole amp needs to be looked at.
Phil.
It had a bad power tube that when you would tap it, it would arch I didn't see any other problems and voltages were good and that is why I fixed the trace and changed the tubes.

phatt

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Re: sound problems with Peavey Classic 50
« Reply #4 on: November 16, 2009, 10:58:00 PM »
Yes but you should be wondering why it was arching in the first place!
I'm not familiar with your amp but I've worked on enough tube gear to say that most are now cutting to many corners. :'(
Read your HT voltage I'll take a stab and say it will be well over 300VDC.
These modern amps really do push the limit and some EL84 amps have voltages closer
to 400VDC,,, Yes it can be done but don't expect long tube life.

now back to the other issue;
The interconnecting harnesses that go between the boards are a common failure point.
Amps like this have so many points of potential failure due to multi switching relays and use of cheap connectors. All the big names are cutting costs, giving many options but with reduced quality. The old stuff had issues but so much easier to fix.

This map might help unravel the needless complexity of your amp.
http://www.blueguitar.org/new/schem/peavey/modnotes/c50twdbm_sch.pdf
I would loose C16 (as shown) for a start, a cap here is kinda strange,, the right
value *in front* of the input will pull some magic tricks but not after the input
where it does little.
Phil.

awdman

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Re: sound problems with Peavey Classic 50
« Reply #5 on: November 17, 2009, 09:38:47 AM »
that's fantastic and I hope one day I will be able to make amps better not just fix them.
« Last Edit: November 17, 2009, 10:35:07 AM by awdman »

phatt

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Re: sound problems with Peavey Classic 50
« Reply #6 on: November 17, 2009, 09:54:12 AM »
Good to hear. :tu:
Phil.

awdman

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Re: sound problems with Peavey Classic 50
« Reply #7 on: November 18, 2009, 10:53:14 PM »
I found the problem to be a bad connection on the effects return board. I agree that cheap connectors are used.

Brymus

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Re: sound problems with Peavey Classic 50
« Reply #8 on: November 18, 2009, 11:09:32 PM »
Interesting as the amp I have that makes that noise is still using the original PCB and connectors VS an eyelet board like I normaly use.
I will check the connectors on mine as well.
Glad you got it fixed.
Did you bypass the connector or use DeOxit or something similar to solve the issue?

awdman

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Re: sound problems with Peavey Classic 50
« Reply #9 on: November 18, 2009, 11:17:47 PM »
I sprayed it with contact cleaner, and then pulled the connector off to make sure all of the wires were seated and plugged it back in and it sounds good.

Anthony

phatt

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Re: sound problems with Peavey Classic 50
« Reply #10 on: November 19, 2009, 06:55:01 AM »
Interesting as the amp I have that makes that noise is still using the original PCB and connectors VS an eyelet board like I normaly use.
I will check the connectors on mine as well.
Glad you got it fixed.
Did you bypass the connector or use DeOxit or something similar to solve the issue?

Consider the *Climate* you live in. Humid climates wreak havoc on cheap connections,
spare a thought for poor sods like me. I live in SE Queensland, Australia,,, 5 khm from world famous beaches. Sounds nice for tourists but had work for us musicians.
It's Hot, Humid,, now add salt air.  :o

Life span of components is definitly reduced where I live. I'm constantly replacing "green gunk coated" output sockets on guitars due to the added humidity.
Phil.

awdman

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Re: sound problems with Peavey Classic 50
« Reply #11 on: November 19, 2009, 07:29:44 AM »
I do notice it more on humid days. Phil you are full of knowledge.   :tu:

 

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