Yamaha CA-1000 problem

Badger

Active Member
I bought this CA-1000 about 7 years ago knowing it had some issues. Now that I'm retired I'd like to see if I can get it working properly. What I've found so far is a great sounding amp in class A. But when I turn it off and switch to class AB I have severe distortion in both channels. I've read that this amp has a problem with the mode switch and that you can sometimes hear arching in the amplifier itself. Mine is dead quiet. Does anyone believe it is still the class mode switch or is there some place else I should be looking to solve the problem? Any help would be appreciated.
 
You should consider moving this post to the Yamaha boards. Much more Yamaha specific info there and usually visited regularly by some very knowledgeable people.

Avionic and Merrylander are Yamaha experts, either of them would be worth a PM.

I have heard of trouble with the mode switch burning its contacts if it is switched with the unit powered up. Cleaning does not usually help as the contacts are burned, not dirty. You may be able to disassemble the switch and resurface the contacts or one of the gentlemen named above may be able to suggest a suitable replacement.
 
There are two micro switches on each side of the physical mechanical switch. The contacts will burn out over time. Mouser p# V-15G-1C25-K is the replacement, order two and replace them.

http://www.tapeheads.net/showpost.php?p=248057&postcount=14
OP---
In the same photo the center slide switch could also have dirty/tarnished contacts. This switch is pretty easy to ohm out using testing points on the driver boards A,B,C and S. If the Omron microswitches don't do the trick. You need to disassemble the center switch and clean the contacts. Just spraying cleaner in the openings don't cut it.
 
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Thanks for your input. I'll order the switches today and go from there. Even if they are not the problem now it sounds like they need to be replaced. I will let you know what happens.
 
The switches came yesterday and I put them in today. Very simple process and the amp sounds great! I checked the old micro switches and one practically crumbled in my hand. Contacts were badly burned. Thanks so much for the advice it saved me a ton of time.:thmbsp:
 
Did you set the bias or at least check it in A and AB? Good to hear you got it working!


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Will do that today. I barely got to turn it on yesterday after I installed the switches because I had to go cook bison dogs on the grill for the 4th. I have the original service manual and will DeOxit all the switches and check the bias before I put it back together. Thanks again for the help.
 
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