KA 9100 repair options

All-ears

New Member
Hey Gang,

I am brand new here so be gentle.

I had a KA 7100 for many years and love the amp. My speakers (Cambridge Soundworks towers) seem to be power hungry. When the 7100 stopped working I bought a KA 9100 on ebay to use while the 7100 was going to be repaired. Fired up the 9100 and it is missing a channel.
I live in Nashua NH, and am looking for a good place to get these repaired. The last thing I soldered was a supply line for the bathroom sink so probably am not up for the repair and diagnostics of these amps myself. And there seems to be some finer points on what capacitors or transistors to use.
Does anyone know a good shop with a tech that understands these amp's in the area? Anything specific to ask them for other than "fix it"?
Thanks
 
If one channel works, the other is probably fine and the signal is likely getting lost in a dirty switch or pot. Usual suspects on the 9100 are the NORMAL/SEPARATE switch on the rear panel and the filter pushbuttons on the front, although pretty much any switch can cause it. Sometimes just exercising them can get back a lost channel, although a thorough cleaning would be the best bet. Could also be any of the pots.
 
Hey Gang,

I am brand new here so be gentle.

I had a KA 7100 for many years and love the amp. My speakers (Cambridge Soundworks towers) seem to be power hungry. When the 7100 stopped working I bought a KA 9100 on ebay to use while the 7100 was going to be repaired. Fired up the 9100 and it is missing a channel.
I live in Nashua NH, and am looking for a good place to get these repaired. The last thing I soldered was a supply line for the bathroom sink so probably am not up for the repair and diagnostics of these amps myself. And there seems to be some finer points on what capacitors or transistors to use.
Does anyone know a good shop with a tech that understands these amp's in the area? Anything specific to ask them for other than "fix it"?
Thanks

Welcome! This is Dan (from eBay). It’s unfortunate that you received the 9100 not working. Definitely worth the effort, nice speakers you have there as well. As gort69 suggested, I’d clean all of your controls with a contact cleaner/lube such as deoxit or similar. Give each potentiometer/switch a good soaking and move them their full range of movement 50 times or so and then another good spritz. Also make sure that the preout/ main in are hooked up correctly.

Soldering plumbing with mapp gas or propane is much different than electronics lol. Do you have a multimeter so you can measure voltage at the amp outputs? Any way of tracing a signal?

Dan
 
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I'm a rookie too.

I've revived a dead channel on a couple of amps with a good Deoxit switch cleaning. (Carver Receiver and a Onkyo Integra cobwebby thing in a recycle pile).

Good luck, beautiful piece of kit. I think I need one...
 
Don't forget to Deoxit the switch on the rear panel labelled Normal-Separated.
 
+1 on cleaning. I have a KA-701 that had a dead right channel. I sprayed all the pots, still no sound. A week later, I sprayed again, worked it in good. Sound cutting in and out (progress!). Another week passes and I saw a solder wart loose on the front panel, so I applied a bit of solder to tighten it up, still cutting out. Another spray and working it in, and now it works perfectly. The point is it can take a few sessions with the Deoxit to clear things up.
 
Welcome! This is Dan (from eBay). It’s unfortunate that you received the 9100 not working. Definitely worth the effort, nice speakers you have there as well. As gort69 suggested, I’d clean all of your controls with a contact cleaner/lube such as deoxit or similar. Give each potentiometer/switch a good soaking and move them their full range of movement 50 times or so and then another good spritz. Also make sure that the preout/ main in are hooked up correctly.

Soldering plumbing with mapp gas or propane is much different than electronics lol. Do you have a multimeter so you can measure voltage at the amp outputs? Any way of tracing a signal?

Dan

Hi Dan,

I do have a multimeter. I'm going to try the spray/cycle/spray trail first. If that doesn't work, is the amp output the just speaker terminals or something on the board?
 
Yes, the speaker outputs on the back of the amp. Turn the amplifier on and leave it on for about 15 minutes. With nothing plugged into the amp and the volume attenuators at minimum hook up your meter probes to the outputs one at a time. So red probe to be positive output and black to the negative, doing the left channel and then the right. When measuring you want your meter to be set to measure mV (millivolts) DC current. You want it to be low, preferably as close to zero as possible.

Dan
 
The DC offset adjustment has nothing what so ever to do with the unit dropping a channel.
 
The DC offset adjustment has nothing what so ever to do with the unit dropping a channel.

Correct it doesn’t, but since he is new at this it’s a good thing for him to check and could give him an idea of what condition the other channel is in.

Dan
 
My crappy opinion is that it really isn't a good idea to go twiddling trim pots without truly understanding what they do, and it could be a little confusing when trying to troubleshoot why sound is dropping out on one channel.
The time will come for checking other aspects of the function of the amp. First, let's just see if we can get sound out of both channels.
 
My crappy opinion is that it really isn't a good idea to go twiddling trim pots without truly understanding what they do, and it could be a little confusing when trying to troubleshoot why sound is dropping out on one channel.
The time will come for checking other aspects of the function of the amp. First, let's just see if we can get sound out of both channels.

Oh goodness, if I was at all implying that the op should crack it open and mess with the dc offset trimmer then yes don’t do that. I said simply measure.

If he has a somewhat equal offset in both channels and only has output from one channel it could tell him the amplifier channel is good and he is losing signal in the preamp section.

Dan
 
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