Distorted right channel in vintage Yamaha CA-610

redbeardo

New Member
Hi all. I've had this Yamaha CA-610 for a while now and it hasn't got much attention. I'm on holidays for the next few weeks and I'd like to get it running in good order if I can.

The issue is the right channel is distorted. I've swapped the speakers through A and B, and swapped them over left and right, it's not the speakers. I've tried every input, phono, aux, tuner, tape, it's the same in every one, right channel distorted. I've opened it up and sprayed a ton of deoxit and turned all the knobs. It works fine through headphones though, no problems there so hopefully that narrows it down a bit.

I've taken a video so you can hear it and understand what I'm talking about. In the video I turn the balance from left to centered to right so you can hear the left and then the right on it's own. You can also see the meters in the video (which I will need to fix the globes at some stage).

Now I'm not the most knowledgeable on the insides of vintage audio, but I'm a keen learner and good at following instructions. I have the manuals and schematics from http://akdatabase.com/AKview/thumbnails.php?album=3&page=4 so if anyone has ideas where to look I can find the places using these.

Hopefully someone can point me in the right direction.

Thanks in advance!

 
It's not a sure bet, but my take is that the symptoms suggest failed output transistors - TR418 and 420, if the schematic is accurate about which amp sections are for the left and right channels.

You can find notes about how to check transistors with an ohmmeter in a sticky thread near the top of the "DIY" forum. That's probably a pretty good starting point.

By the way, people who know more than me about the CA-x10 series are regulars in the "Yamaha" forum (in the manufacturers section of AK). If the going gets tough, that might be a better place to get help.

Hope this helps,

chazix
 
It's not a sure bet, but my take is that the symptoms suggest failed output transistors - TR418 and 420, if the schematic is accurate about which amp sections are for the left and right channels.

You can find notes about how to check transistors with an ohmmeter in a sticky thread near the top of the "DIY" forum. That's probably a pretty good starting point.

By the way, people who know more than me about the CA-x10 series are regulars in the "Yamaha" forum (in the manufacturers section of AK). If the going gets tough, that might be a better place to get help.

Hope this helps,

chazix


Awesome thanks chazix. Time to learn about transistors!
 
Hold your horses on the transistors.

What does the right channel sound like with the stereo/mono switch in the mono position ?
 
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Does jiggling the speaker select switch make the issue better or worse?
 
Does tapping on the protect relay have any effect on the issue ?
 
It works fine through headphones though, no problems there so hopefully that narrows it down a bit.

How does the right channel sound through the headphones ? Plenty of volume ? Clean ?
 
Thanks for the replies avionic, this is my first attempt at replying to multiple quotes in one reply, hope this works...

Hold your horses on the transistors.

What does the right channel sound like with the stereo/mono switch in the mono position ?
When I flip it to mono there is the ever so slightest decrease in volume, almost unnoticeable, tried with both speakers and headphones, same result.

Does jiggling the speaker select switch make the issue better or worse?
Jiggling seems to have no effect

How does the right channel sound through the headphones ? Plenty of volume ? Clean ?
When the speaker select switch is selected off so the sound is just through the headphones it is great, clear and loud! But when I flick it on to A or B or A+B and the sound is coming out the speakers as well as headphones, then the right headphone channel is also distorted

Does tapping on the protect relay have any effect on the issue ?
What is a protect relay? I had a look in the parts list in the manual to try and navigate it and couldn't see it, what does it look like?

Thanks again for replying, I hope this helps!
 
When you first flip the power switch. There should be a short delay then a "click" .... then sound. The "click is the protect relay. In the CA-610 the relay is a plastic box maybe approx. 1"X 1/2 " X 1" either clear plastic or black plastic.Located on the main circuit board.
 
Should look similar to these. FRL-264's
index.php
 
When the speaker select switch is selected off so the sound is just through the headphones it is great, clear and loud! But when I flick it on to A or B or A+B and the sound is coming out the speakers as well as headphones, then the right headphone channel is also distorted

Doesn't this mean that the speaker selector switch needs some work (really good clean, ok, you've done this).
Does turning the speaker selector very slightly anti or clockwise have any effect, ie, slightest wiggle

The speakers will have a lower impedance than your headphones, causing the amp to work harder, bringing on the
distortion and explain your observation.
 
Doesn't this mean that the speaker selector switch needs some work (really good clean, ok, you've done this).
Does turning the speaker selector very slightly anti or clockwise have any effect, ie, slightest wiggle

I just gave the speaker select switch another big spray of contact cleaner from above, below and through the front. No effect with any turning or wiggling to any degree in either direction
 
It works fine through headphones though, no problems there so hopefully that narrows it down a bit.

For what it's worth, this observation in the original post was key in my theorizing output transistor failure. I thought (and still do) that the transistors are likelier suspects than the relay or speaker switching, because the latter would be very likely to be temporarily "cured" when the volume is cranked up into a speaker load, but that doesn't happen.

Still, avionic in particular is one of the people who knows more than I do about this series, so I'm prepared to be proven wrong!

Cheers,

chazix
 
For what it's worth, this observation in the original post was key in my theorizing output transistor failure. I thought (and still do) that the transistors are likelier suspects than the relay or speaker switching, because the latter would be very likely to be temporarily "cured" when the volume is cranked up into a speaker load, but that doesn't happen.

Would have to agree.

Speaker selector ruled out.
 
Guess its time to test those outputs and emitter resistors.
 
What about using a PC based CRO, eg,

https://www.zeitnitz.eu/scope_en

I use it as a signal generator while saving up for the real thing. Also my cro died before Christmas so I'll probably
use it. Can't see it being much good, but should be ok for audio frequencies. Uses a 3.5mm stereo jack, ie, need to
make up your own probes. Also there has been talk that it's tough on the sound card, so if you have an old pc...

The amp appears to test ok when doing nothing/little work (ok through headphones) but starts to fail when pushing
"8 ohms". You might get lucky with static testing of TR's etc but...

The above scope is a free download.
 
Right I'm reading up on how to test, I've bought a multimeter and will get to it over the weekend. Stay tuned folks!
 
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