Need help with vintage Onkyo power amp.

dave123456@mail · 30th December 2008, 07:41 AM

Hi,

I have a vintage onkyo power amp that is decent sounding, but has a problem with one channel fading in and out. The lower the volume, the worse the problem but seems to go away when I turn the volume up reeeeally loud, and then turn it back down but only works for a few minutes...and them bam back to the problem with the sound cutting out from one channel ( usually the right channel doesnt work but sometimes its the left).

What do you think is going on here guys? I'm looking for some possible solutions that will allow me fix the amp myself and not have to buy another one.

Bigred · 31st December 2008, 09:36 PM

You say its a POWER AMP so assuming your running a pre-amp, it sounds like dirty controls. I'd clean all the controls and switches (caig deoxit and faderlube work wonders). Unless you meant an integrated amp or receiver etc. The same would apply, I'd start by cleaning all controls and switches. If indeed it IS a power amp, you can always isolate that the amp is at fault by using a known good source direct to you amp providing either the source or amp has a means to attenuate the signal. More details about your setup and what amp etc. would be nice.

XEAGLEKEEPER · 1st January 2009, 12:42 AM

My also want to take a look at the speaker protect relay . The relay contacts my be fouled ie dirty, tarnished or whatnot.
You can pry the plastic cover off and burnish the contacts with a emery board.
It takes more current to transfer the signal through the dirty relay contacts -- would explain the necessity to increase the volume for a more stable sustained output.

dave123456@mail · 1st January 2009, 09:03 AM

Hey red,

Thank you for the reply. The power amp is a Onkyo m-5150 and the pre amp is a Onkyo p-3150v Both are from the 80's and were bought at a swapmeet.

I know for sure its the power amp because I hooked the preamp to another amp and it sounded fine. I also noticed when I wiggle the speake wire this help a liiiitle ( and i mean barelly) maybe its the speaker wire connections?

rocco gibralter · 1st January 2009, 08:30 PM

It'll be some flakey connection. I had hiss that was driving me nuts, finally found, One leg on a 10uf cap had gone dry causing all the trouble, While you've got in in bits it might be worth giving the whole thing a careful once over!!

good luck!

dave123456@mail · 2nd January 2009, 03:33 AM

Wow, thanks for all the helpful replies guys! I tried to ask the same question on another forum ( not going to name names) and the only thing they told me was to throw it away. This is a great site. I will take apart the Onkyo when I have more time and try some of the methods suggested.

30th December 2008, 07:41 AM	#1
dave123456@mail diyAudio Member Join Date: Dec 2008	Need help with vintage Onkyo power amp. Hi, I have a vintage onkyo power amp that is decent sounding, but has a problem with one channel fading in and out. The lower the volume, the worse the problem but seems to go away when I turn the volume up reeeeally loud, and then turn it back down but only works for a few minutes...and them bam back to the problem with the sound cutting out from one channel ( usually the right channel doesnt work but sometimes its the left). What do you think is going on here guys? I'm looking for some possible solutions that will allow me fix the amp myself and not have to buy another one.

1st January 2009, 12:42 AM	#3
XEAGLEKEEPER diyAudio Member Join Date: Jan 2006 Location: central Iowa	My also want to take a look at the speaker protect relay . The relay contacts my be fouled ie dirty, tarnished or whatnot. You can pry the plastic cover off and burnish the contacts with a emery board. It takes more current to transfer the signal through the dirty relay contacts -- would explain the necessity to increase the volume for a more stable sustained output. __________________ Ret. USAF... AKA- Avionic * Solder slinger for hire...*

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31st December 2008, 09:36 PM	#2
Bigred diyAudio Member Join Date: Jul 2007	You say its a POWER AMP so assuming your running a pre-amp, it sounds like dirty controls. I'd clean all the controls and switches (caig deoxit and faderlube work wonders). Unless you meant an integrated amp or receiver etc. The same would apply, I'd start by cleaning all controls and switches. If indeed it IS a power amp, you can always isolate that the amp is at fault by using a known good source direct to you amp providing either the source or amp has a means to attenuate the signal. More details about your setup and what amp etc. would be nice.

1st January 2009, 09:03 AM	#4
dave123456@mail diyAudio Member Join Date: Dec 2008	Hey red, Thank you for the reply. The power amp is a Onkyo m-5150 and the pre amp is a Onkyo p-3150v Both are from the 80's and were bought at a swapmeet. I know for sure its the power amp because I hooked the preamp to another amp and it sounded fine. I also noticed when I wiggle the speake wire this help a liiiitle ( and i mean barelly) maybe its the speaker wire connections?

1st January 2009, 08:30 PM	#5
rocco gibralter Account disabled at member's request Join Date: Aug 2008	It'll be some flakey connection. I had hiss that was driving me nuts, finally found, One leg on a 10uf cap had gone dry causing all the trouble, While you've got in in bits it might be worth giving the whole thing a careful once over!! good luck!

2nd January 2009, 03:33 AM	#6
dave123456@mail diyAudio Member Join Date: Dec 2008	Wow, thanks for all the helpful replies guys! I tried to ask the same question on another forum ( not going to name names) and the only thing they told me was to throw it away. This is a great site. I will take apart the Onkyo when I have more time and try some of the methods suggested.

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