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Kenwood KA9100 Lost Channel

jocko_nc

jocko_nc

Super Member
I broke out the sweet KA9100 last weekend to hook up the the daughter's bedroom system. I was shocked to have no sound out of one channel. That amp had been fine a year or two ago, I figured I had a bad connection in the 30 year-old speaker terminals. Nope, I have a dead channel. &^$%#$#$!

It ain't the speakers or the cables. The preamp section seems to work. I never put headphones on it, but both output needles move. I assume they really measure preamp current and signal is there.

I know the outputs are 100% unobtainium. Before I look, is there a fuse or something stupid to look for? Poor solder connection? If an output was blown, would the amp switch out of protection?

I'm really reaching in desperation here...
 
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If both output meters move, and the speaker connections are good, it almost certainly points to the speaker switches. Try cleaning them.

Unfortunately the service manual doesn't show very much, and that part of the amplifier isn't in it.
 
I've got one that needs a good de-oxit bath. The balance knob or cycling either sub/high filter switch usually smartens it up.

Also, there is a split amp/pre switch on these. Try cycling that a few times with the power off?
 
There is an amp-pre switch. It still has the plastic cover on it. I bet it has never moved.

So you think there is hope since the meters move? Please explain. That would be such good news.

Aside: I was surprised how clean the "usual suspect" pots were: Stereo / Mono. Balance. Loudness. I have neve come across speaker switch contacts dirty enough to cause a channel to drop out.
 
If both meters are working I believe their references are from the preamp side. I'd still pop that plastic doohickey off the seperate switch and give it some movement. Funny things happen to items that just sit around.
 
You can also pull a line signal from another pre and feed to the power amp section to verify its working as well.

Good luck.
 
From what I can glean from the service manual, the meters are on the output of the amplifiers. That's why I said the problem is probably in the speaker switching circuit.
 
More KA9100 woes

cabinover said:
I've got one that needs a good de-oxit bath. The balance knob or cycling either sub/high filter switch usually smartens it up.

Also, there is a split amp/pre switch on these. Try cycling that a few times with the power off?
Click to expand...

Well, I picked up one of these this weekend. Plan to give it to my nephew for his HS grad present. Tested it at the guy house and everything worked. Got it home and no sound at all. Lights work, meters moved, but complete silence.

I would really like to know the final outcome of this thread....
 
kwingylee said:
Well, I picked up one of these this weekend. Plan to give it to my nephew for his HS grad present. Tested it at the guy house and everything worked. Got it home and no sound at all. Lights work, meters moved, but complete silence.

I would really like to know the final outcome of this thread....
Click to expand...

Check to make sure that the PRE-Out/Main-In switch on the back is in the connected position and then try if it works.
 
Not the pre/power amp switch

I tried the switch today as suggested. I still do not have any sound.
I hooked up the headphones and they sound great! I get head phone sound regardless of the speaker select switch position: OFF, A, B, A+B.

I looked at the speaker selector switch and it turns real nice, I can see the ball on the switch making contact. I don't think its the switch.

Both power meters work great. The move nicely.

The relay sounds ok, I hear the clicks.

All fuses checked out.

According to the schematic, there are only two items: the speaker switch and the relay. I don't think I can replace the switch. But I am willing to bet on the relay. Do you guys know what the equivalent relay is today?
 
Well, from looking at the block and level diagram, the relay is after the amp, after the amp is the meters and after the meters is the speakers.

So, if the meters are moving and everything then I really don't know what could be wrong. Theirs no way you could replace the speakers selector since those are long out of production and the only way to get one is by getting a parts unit. But possibly its the relay, maybe? But if its theirs a problem with the relay then the meters would not be working.
 
IHA...

I agree with you. I found a KA9100 schematic from a previous thread. I am either not making any connections to the speakers from the terminal out or the speaker selector switch is not working!

The phone jack sound cannot be turn off. Which means if your phones are plugged in, you will always hear something. Regardless of the switch setting.:scratch2:

I am going to try to bypass the switch next.....

The relay seems ok..unless is stuck close. I can hear it clicking turning power up though...:scratch2:
 
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