My first Kenwood

scottstevens

Well-Known Member
A KA-9100.

Seems to work great and all, except at low volume. Then the right side doesn't work, kind of fades in and out. When you crank the volume up for a while then it's ok. Seems to be a common thing in old amps? My Sony TA-4A does the same thing. You have to warm it up for a while, then it balances out.

I guess it needs a good deoxit? I tried using another kind of contact cleaner which has helped a bit. I found deoxit gold, so I bought that but I don't have the D5 yet. Another store has that. I believe I use the D5 first, then give it the gold?

Some pics.

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Thanks for that!

Do you think it worthwhile to just replace the big 4 caps? I could do that, but not recapping the entire unit.
 
Look underneath the filter caps to see if they are leaking. If they are leaking you should replace right away due to corrosion and power supply issues. If they are not leaking you may have some time with them. Larger caps will tend to hold their electrolyte longer simply because they are starting with more of it. If you replace them yourself, take a lot of picture before and make absolutely sure you have the polarity right afterwards. If you get it wrong, it will be catestrophic when you power up.

Your low volume issue is most likely a dirt/corrosion issue in the switches and the volume and balance pot. Cleaning this unit will probably do wonders. You have a fine piece of equipment that you would be hard pressed to find something like today in a new version. Keep it and spend the money to have it rehabbed and recapped when you can. You won't be sorry.
 
Sometimes the caps look good from the top but the boards on the bottom may conceal bulging or a small leak. The boards are easy to remove with a good soldering iron and solder sucker or large solder wick. Example of the left channel board removed. (good caps) FYI: the protection circuit for this unit is on this board.
John M

http://audiokarma.org/forums/showpost.php?p=7276205&postcount=70
 
That is one sweet, FIRST Kenwood! Amp looks to be separate right down to the power transformers. Nice. Don't know if the preamp uses a single power supply or separates?! Not the recap expert so can't answer the question, but others here will probably give you their real world experience.
As far as the volume pot, a lot of commercial gear has extremely high gain and commercial pots of that era aren't matched so good, channel to channel. You will notice that most when the volume is low. If it isn't an actual potentiometer problem then lowering the input source level allows you to run the volume pot a little higher where the mismatch is less noticeable. I do that on a separate amplifier with input levels so that I don't notice the channel to channel mismatch of the preamp volume pot when listening at a low level, but that isn't so easy on an integrated amp. Nice acquisition.
 
Thanks for the info guys. My wife is out and will grab a can of deoxit for me, hopefully later I can clean up some of the controls. When I'm feeling brave, I'll have a look at the bottom of the caps.
 
ScottS-- if it makes you feel better, of all the 9100's I've worked, only a few of them had bad caps. If they show no sign of fault then you could get away with keeping them in but for an older unit replacement should be on the list. Caps get old and dry out.
Alot of probs with these are in the controls and pots. Deoxit the switches and pots and then use the lube or gold to do the pots over. This prevents the carbon in the pots from cracking because the deoxit dries them out. Good luck with it. The 9100 is an excellent amp/preamp.

John M
 
Does it take a volume spike to get the channel to come back? If so, it could be a bad relay, dirty keeping the low signal from getting through. Replacement is indicated.
 
oh boy, been a while!

when I first got my 9150 I had the same issue... I also purchased a SM which had an addendum that directed me to the filter section? and, low and behold, after cycling them a dozen times or so (w/o contact cleaner) I was good to go on both channels.

can't hurt!

good luck!
 
Does it take a volume spike to get the channel to come back? If so, it could be a bad relay, dirty keeping the low signal from getting through. Replacement is indicated.

Thanks, I'll have to take it to a shop then. Yes, i have to crank it up, then the sound comes though both sides.
 
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