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KA-5700 Left Channel Losing Output

nicklynn1

nicklynn1

AK Member
My KA-5700 left channel output is slowly declining. This is based on the watt meter outputs reading lower in the left channel than the right and also the sound from the left speaker is less than the right, primarily the bass. I have done the following easy things with no luck isolating the issue:

1-switched speakers to opposite channels,
2-deoxed all switches and controls,
3-set the tuner to mono,
4-set the amp input to tuner directly vs. going through the GE-1100 equalizer,
5-validated that the same phenomenon occurs with the CD player,
6-visually looked for any damaged components.

The sound difference is more pronounced when the bass is turned up. Getting ready to start checking components...any advice where to start? Output transistors? I was just going to jump into a recap, but would really like to nail the issue vs. taking the shotgun approach. I did notice a capacitor with what looks like a lot of glue and/or leakage under it. I'll have to remove the cover again to ID which one it is.

Thank You,
Nick
 
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Output trannies are the least likely culprit. And, I assume that you actually hear that there's a problem rather than rely on the meter to tell you that there's a problem.

My first thoughts would be the speaker select switch and/or the speaker protection relay. And since the tone controls are embedded in the feedback loop and cannot be bypassed, dirty tone control pots can cause problems as well.
 
Thank you for the feedback. :thumbsup:

Yes, I used the balance control to listen to each channel independently and there is a significant difference between left and right that is easy to hear. The right channel has a lot more bass and just sounds louder, yet slightly muddy compared to the left one. I will deox the switches again and pay particular attention to them. The tone control pots and volume control are relatively easy to get at, so I am pretty comfortable that they were cleaned well. I also moved the input cables on the back of the amp from left to right channel just to see if the issue was amp or device related, and the problem didn't move so it looks like an amp issue.

I'll have a chance tomorrow to get back at it and will let you know how it worked out.

Thanks again...
 
Today I cleaned all the switches and pots again with Deoxit5. No improvement. I then disconnected my 4ohm speakers and hooked up my 8ohm speakers to see if that made a difference and it didn't. Same difference in sound. It is more noticeable when I turn the bass up and when the volume is turned up. I also noticed that if I turn my tuner to a frequency with no station, just static, the meters read the same and the sound is balanced between the speakers. Also, the right channel, which has more bass, will hum with feedback if I turn up the bass enough and the left channel does not.

Do any of these clues point in a different direction?

Thanks,
Nick
 
Are you suggesting that, with a tuner input, all is OK? What input are you using when you hear a problem?
 
All inputs have the same issue. I was trying to rule out the left and right inputs by setting the tuner to mono vs. stereo and then just for kicks tuned it to static to see if they were different and they weren't. There isn't much bass in static so maybe that is why it wasn't noticeable. Also is present with phono input, tape A input, tuner input. At this point I am trying to isolate where the problem is most likely at. Thanks again for the feedback and your help.
 
Hey Nick, I resolved the issue I was having with my 5700 where the left channel audio sounded tinny and much louder than the normal sounding right ch. It's basically the opposite of what you're experiencing. Mine was present with all inputs, but I noticed it cleared up when I moved the speaker switch. I cleaned the switch and thought it was good, then it came back. I fiddled with the switch and it cleared again, then I made it fail. I opened the cover and began tapping and touching components near the speaker switch. At first, I was messing with anything near that switch on the board, but began focusing on the electrolytics since I had recently (about 1 month) replaced all of them. Sure enough, I had a cold solder joint on one of the new caps. I thought I had paid close attention to that during the recap, but sometimes haste is easy to fall prey to when you think the task is rudimentary. Re-flowed the solder and all is well. Do you have a copy of the service manual? I would start making voltage measurements and comparing the two channels. I can send you a pdf if you need it. Good luck and post what you find.
 
Thanks for the reply and I will be back home in a few days and will check that area. I do have a service manual and I'll post the results.
 
It's been a while but...I did a few things and it went away. Not sure what did it though.
1-Checked speaker wires and one was 3 in longer than the other so I made them equal. The wires are 12' long and are being used with 4 ohm speakers.
2-Moved the amp the same distance from each speaker. It was much closer to the right one and that is the one that was sounding like it had more bass...feedback maybe? They are now 6' away from the amp.

Doesn't make any sense to me but it worked. Something else may have 'healed' itself and I'm just not aware of it.

Thanks for the feedback and have a Happy New Year.
 
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