[Pudu]

Quick question.


The right channel on my 980 has for a while been getting more staticy and quieter. Eventually it dropped out altogether. But the headphone out sounds as good as ever. Today I pulled it apart and applied deoxit to the balance and volume pots. Since I had it open I checked and adjusted the DC offset, which was quite off on that channel.

Now she sounds great once again. But the question I have is what caused the channel drop out? Can bad offset do that? Was a combination of both things that lead to static and then drop out?




Alright, that was three questions.

 

[PhoenixG]

Quick question.


The right channel on my 980 has for a while been getting more staticy and quieter. Eventually it dropped out altogether. But the headphone out sounds as good as ever. Today I pulled it apart and applied deoxit to the balance and volume pots. Since I had it open I checked and adjusted the DC offset, which was quite off on that channel.

Now she sounds great once again. But the question I have is what caused the channel drop out? Can bad offset do that? Was a combination of both things that lead to static and then drop out?




Alright, that was three questions.

I'm not sure about the static - that was probably mostly the dirt, but a way off DC offset could cause the protection circuit to trip once it gets hot.

 

[hojomojo96]

There's no a cracking on the cap that I can see - as for leakage, I don't see anything but I'm not sure if I'm looking for the right things. I did check, and the cap doesn't get hot while playing.
Just out of curiosity, how hot should these receivers be running on average? I don't think I'm even close to a dangerously hot temperature, some parts are warm to the touch, but they don't burn. Still figured I should check, though.

 

[af0h]

There's no a cracking on the cap that I can see - as for leakage, I don't see anything but I'm not sure if I'm looking for the right things. I did check, and the cap doesn't get hot while playing.
Just out of curiosity, how hot should these receivers be running on average? I don't think I'm even close to a dangerously hot temperature, some parts are warm to the touch, but they don't burn. Still figured I should check, though.

If there was any leakage, it would show up on the board below the cap - or at least running down the legs of the cap.  Most of the film caps I've seen that did bust either cracked also or bulged out on one side or the other, but I never did see one blow up like a balloon.
 
Temperature wise - these older receivers do run warm, hense the large heatsinks on the output transformers.  As long as it doesn't get too hot (so hot you can't hold your finger on it for more than a couple of seconds) then it sounds like everything's running fine.  If you want to get creative and perform a little diy, a small Brushless DC cooling fan can be installed for a bit of extra cooling, but it sounds like you're running 100% normal to me.  Of course you'd have to tap into a low-voltage power source to power the fan - either from inside the receiver itself or you could go with an external power supply if absolutely necessary.   I did this with an old Sansui years ago and tapped a 12-volt line feeding a 7805 regulator to power the fan.  The fan running at such a low speed made no noise at all, but was still effective at moving some air across the heatsinks.

 

[hojomojo96]

 
If there was any leakage, it would show up on the board below the cap - or at least running down the legs of the cap.  Most of the film caps I've seen that did bust either cracked also or bulged out on one side or the other, but I never did see one blow up like a balloon.
 
Temperature wise - these older receivers do run warm, hense the large heatsinks on the output transformers.  As long as it doesn't get too hot (so hot you can't hold your finger on it for more than a couple of seconds) then it sounds like everything's running fine.  If you want to get creative and perform a little diy, a small Brushless DC cooling fan can be installed for a bit of extra cooling, but it sounds like you're running 100% normal to me.  Of course you'd have to tap into a low-voltage power source to power the fan - either from inside the receiver itself or you could go with an external power supply if absolutely necessary.   I did this with an old Sansui years ago and tapped a 12-volt line feeding a 7805 regulator to power the fan.  The fan running at such a low speed made no noise at all, but was still effective at moving some air across the heatsinks.

Mmkay, thats what I was looking for - I don't see any. I will at some point attempt to recap this myself, though, just to be safe and to have it running at its peak. I'm a high school kid though, and I basically learn by doing, but I'd rather not break this. Is there anywhere I can find a really simple guide on recapping in general? Obviously not model specific. 
 
And good to know. I'm fine with the temperature that its running at, so I guess I'll be building it a vented wooden case soon. I can't justify buying one online when I could build the same. I don't think I'll be experimenting with fans quite yet, though.

 

[af0h]

  Is there anywhere I can find a really simple guide on recapping in general? Obviously not model specific. 

http://audiokarma.org/forums/showthread.php?s=59fcc8ffe96e700f49abf7c29ca2b107&t=122359#post1298370
 
The above link is an old AK thread (with links at the bottom) that will describe the process and list the materials you'll need.
It's not much, but it is something to go by on short notice.

 

[newfer]

I have an Onkyo A-45 that I bought new in the early 1980's. It's still with me to this day. I use it in my home project studio to power my Tannoy NFM 8 monitors. This thing is a work horse. Aside from a couple back lights not working on the input selector switches it's been rock solid reliable. I recently gave the volume control a cleaning with some basic electronics spray cleaner because it was getting a bit scratchy; clean as a whistle now. You can't find audio equipment made like this anymore, at least not for the price I paid for it. No China built on this, Japan all the way! I'm hoping to get many more years out of it. A classic piece!

 

[Oregonian]

  I have an Onkyo A-45 that I bought new in the early 1980's. It's still with me to this day. I use it in my home project studio to power my Tannoy NFM 8 monitors. This thing is a work horse. Aside from a couple back lights not working on the input selector switches it's been rock solid reliable. I recently gave the volume control a cleaning with some basic electronics spray cleaner because it was getting a bit scratchy; clean as a whistle now. You can't find audio equipment made like this anymore, at least not for the price I paid for it. No China built on this, Japan all the way! I'm hoping to get many more years out of it. A classic piece!

Welcome to the best thread on Head Fi!  When you get enough posts built up, please post a pic of the Onkyo.

 

[Pudu]

I'm not sure about the static - that was probably mostly the dirt, but a way off DC offset could cause the protection circuit to trip once it gets hot.

If the protection circuit cuts in doesn't that shut off everything - to both channels?

 

[PhoenixG]

If the protection circuit cuts in doesn't that shut off everything - to both channels?

I guess they usually do. Good point. Maybe just start with deoxit and see what else you find in there.

 

[jnorris]

Quick question.


The right channel on my 980 has for a while been getting more staticy and quieter. Eventually it dropped out altogether. But the headphone out sounds as good as ever. Today I pulled it apart and applied deoxit to the balance and volume pots. Since I had it open I checked and adjusted the DC offset, which was quite off on that channel.

Now she sounds great once again. But the question I have is what caused the channel drop out? Can bad offset do that? Was a combination of both things that lead to static and then drop out?




Alright, that was three questions.

The headphone output on most older amps was just the speaker output padded down with resistors. If your headphone out is ok but the speaker is cutting out I would look at poor connection/oxidation at the speaker terminal itself. If the volume and balance pots were malfunctioning you'd hear it both on headphones and speakers.

 

[Pudu]

Thanks for the replies PhoenixG and jnorris, much appreciated.

That was how I understood the HO to work on this too. Strange. As I said the only thing I did was clean the pots (and that volume pot is a beeotch to get at) and do the offset. And now it sounds as good as new. I did test it before the maintenance, and the right channel of both A and B outputs was affected.

 

[Skylab]

Quite true...and also if your amp has speaker selector switches (which most vintage amps do), those should be thoroughly cleaned/deoxit treated.

 

[SpeakerBox]

Quite true...and also if your amp has speaker selector switches (which most vintage amps do), those should be thoroughly cleaned/deoxit treated.

 
+1.  The speaker selector switch is where I would look.

 

[Pudu]

Thanks guys. Will look there directly if the issue arises again.

I'm still amazed at how this old thing can still make me stop and be seriously impressed at how good it sounds. I'm quite sure I'd get rid of my other, new amps before saying goodbye to this one.