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Carver C-1

363watt

363watt

New Member
Hello Audiokarma members. I just picked up a Carver C-1 preamplifier with a malfunction and looking for some assistance.
When using Main 2 left and right RCA connenctions output sound is normal, when using Main 1 left and right RCA connenctions the amplifier is pushed to almost full output with the loud tone sound.
Volume control is all the way down.
When using one of each Main RCA connections regardless of left or right it operates normal. It's only when using both.
I disassembled the cover and only spotted one jumper that had the little discoloration, other than that I found no other obvious visual clues.
Please let me know if you have any suggestions.
 

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So it works using the Main 2 output jacks and it does not work using the Main 1 set?

When using one of each Main RCA connections regardless of left or right it operates normal. It's only when using both.

I do not understand what you are doing here. Are you saying if you use only one channel at a time all 4 work?

I would deoxit the switches and check the connections for the rca jacks it sounds like a grounding issue
 
Thanks for the quick reply. What I am trying to say is if I use both rca connections for main 2 I will probably melt down the speakers and amp. I fear trying this too many times.
Please let me know if you have any other suggestions.
 
If I was working on this I would be using my scope and a signal generator no amp involved.
Verify the connections on the rca jacks using an ohm meter
 
I sent the signal out from the trouble main out to my graphic equalizer with spectrum analyzer and see a 60 Hz almost full db reading. This is with either wire connected or both.
If I take one of rca cables and connect to the good main outs the 60Hz is gone.
I ran a jumper wire on the ground outer shell of the RCA and touched another RCA ground and the 60hz hum is gone.
I'm guessing the ground is open on this circuit.
 
Also the Main 2 output has a higher gain than main one if you look at the service manual you will see this.
It also talks about how to change main one gain by changing some resistors you could add the same resistors to main 2 if you wanted to
 
I found the root cause. The trace for this main output ground is missing on the circuit board. J12. See picture.
 

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Wow, I think you're lucky to have found that.

I've had my C-1 for almost 30 years and it hasn't seen near as much use as it should have. At this point, I really, really regret letting go of the Carver amp that I had with it.
 
I'm actually kinda maybe sorta just thinking about getting a C-1 or C-4000 to go with my twin c-500's. The only thing really stopping me is laziness…no remote.
 
Thanks for the compliment waynec. I'm an auto repair tech by trade, but like tinkering with electricity.
I think this C-1 may have previously fried the m400t it was connected too with that kinda 60hz output. The m400 just blows the fuse instantly now.
The advice I got so far is of major damage to the m400, but I peaked inside and don't see nor smell burns in the circuitry.
Any advice would be greatly appreciated.
 

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