Kenwood KA-9100 left channel issue in stereo?

JesseS

New Member
Hi folks! I haven't seen this issue in other threads and hope someone might have a helpful idea here. Sorry if I am duplicating - please link me to the other post(s).

My Kenwood KA-9100 amp recently developed an issue that it cuts sound to the left speaker in stereo. The sound is either super low volume or distorted / with static just on the left speaker. If I flip to mono the sound is equal and great on both sides. If I flip to reverse stereo, the issue is reversed, so I know it is not just the speaker. I run only one set of speakers on the A circuit, a vintage pair of Polk 5jr monitors. For a while, I thought the issue was dirt in the bass adjustment knob and/or in the subsonic filter button because wiggling or pushing there changed the signal loss audibly. But again, since it only happens on stereo settings, I wonder if it is really as simple as a cleaning? If so, please advise - I have some Deoxit but haven't been sure where exactly to spray, from outside or by removing the top cover. I seem to remember that these pots are not easily accessible even with the cover off, and I don't want to do any serious disassembly at home. (In case it matters, I am using the amp on phono and aux mostly, to either listen to records or stream audio via an Apple airport express wi-fi using the aux input. Same problem with both sources. I do have a tuner hooked up, the matching KT-7500, just haven't had much luck with antenna reception here yet...)

If all else fails, maybe someone can recommend a trustworthy and friendly repair tech around Scottsdale / Phoenix?

Thank you!!!!!
 
Those switches (sub-sonic and hi-filter) are notoriously problematic. In fact Kenwood issued a service bulletin on them back in the day.

To clean them, you only need to remove the bottom cover. Set the unit on its left side for the best angle for cleaning. Good light and good reading glasses if you're old like me. Not too bad at all.

Although the switches are pushbutton, the mechanisms move from side to side. Push the buttons IN and you will see two brass colored rails - that is where you want to spray your cleaner so that it runs through. Cycle each switch 20-30 times, then give each another dose and cycle them again. Don't be bashful - it might take a few cleanings.

 
I just rebuilt one of these (with lots of help) and have experienced the same problem 2 times in the last 3 months since finishing the rebuild. After fiddling with all the switches the first time it happened, I found the "stereo/mono/reverse" switch was the culprit. Each time, another round of "Deoxiting" clears it up. Only problem of course, is the innards of that switch are really buried, and disassembly to really access it requires a full teardown of the front end. My compromise was to rest the amp face up, bury the nozzle as far into the front of the switch as possible, and spray the sh*t out of it. I then let it rest for a half hour or so face up, (periodically working the switch of course) figuring gravity would help the cleaner work it's way down there.
It has worked so far, hopefully it won't keep coming back, I REALLY don't want to take this whole thing back apart so soon.
 
Kenwood had a recall on those 2 pushbutton switches (defective) quite a while ago and called for their replacement.
Some of them may not be able to be cleaned permanently. I'm sure alot of these have not been done., "if" I can't get them to work for any length of time in this case I just jumper out those switches on the back of the PC board as a last resort rather than take that assembly apart which is a PITA to do. Besides, do you really use them?

Good luck.
my .02
John
 
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