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Yamaha C2X on the bench

goldswimmerb

goldswimmerb

Failed out of engineering, but look at me now!
Subscriber
Hey all, looking for some advice regarding this model as it's the first I've seen.

Upon testing it does work, however the phono stage sounds like a rain storm, in both channels. I've already cleaned up the switches and selector, as well as the rear switch just in case.

I have the phono shorting plugs in so in theory it should be almost dead quiet.

My guess, since it's both channels is that the power supply section is the culprit, however, without a schematic I am unable to search all that much.

Anyone have any advice for this model of preamp? Looks to be exceptionally well built.
 
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You have arguably one of the finest of the Yamaha pre-amps. It is different from the predecessors C2 & C2a. I always purchase a physical service manual for all my special vintage equipment. The C2X is so worth this since it’s rare and valuable. HiFi Engine may have copies of the manuals for free, but the physical manual is the ticket. Avionics and others here can help technically. I will be watching to pick up pointers. But for myself (very limited electronics know how) being able to bring the service manual to my tech is critical. I have learned to find simple issues just reading the thing.
YMMV, and FWIW. Good luck restoring this wonderful preamp. I’m a bit jealous, but will have to be satisfied with my vintage C2 this afternoon.
Cheers Chris
 
ChristopherP said:
You have arguably one of the finest of the Yamaha pre-amps. It is different from the predecessors C2 & C2a. I always purchase a physical service manual for all my special vintage equipment. The C2X is so worth this since it’s rare and valuable. HiFi Engine may have copies of the manuals for free, but the physical manual is the ticket. Avionics and others here can help technically. I will be watching to pick up pointers. But for myself (very limited electronics know how) being able to bring the service manual to my tech is critical. I have learned to find simple issues just reading the thing.
YMMV, and FWIW. Good luck restoring this wonderful preamp. I’m a bit jealous, but will have to be satisfied with my vintage C2 this afternoon.
Cheers Chris
Click to expand...

I wish it was my preamplifier, I take on work for a small shop and this was one that came in for restoration, trying to figure out all what to do. Managed to get a schematic, and I think I've already solved the hiss, every single cap in the small regulated power supply was 50%+ out and several were testing as "not caps". Gotta figure out what to use for the big filters
 
I get it. Sounds like an interesting project. Search for previous threads on these pre-amps. Glad you found the schematic. As I said, Avionic is a resource for questions. But you should be able to search and find several builds which may solve issues. Caps aren’t a surprise. There are some comments on threads which suggest specific brands and levels. Good luck.
 
avionic said:
Did you remove / disassemble and properly clean the switching contacts ?
Click to expand...

I was able to solve the hiss/noise by recapping the regulated supply, it was oscillating and not filtering. Every single cap was 50+% out, a few no longer tested as caps. Switches seem to be working just fine, no strange noises.
 
avionic said:
Great...Press on...
Click to expand...

What is generally recommended when doing a restore on these? I've done a few C-60 and C-80s and for the most part all they really need are electrolytic caps. Judging by the build of this one I assume the same holds true here.
 
goldswimmerb said:
I was able to solve the hiss/noise by recapping the regulated supply, it was oscillating and not filtering. Every single cap was 50+% out, a few no longer tested as caps. Switches seem to be working just fine, no strange noises.
Click to expand...

Was the MM or MC or both that were noisy?
 
goldswimmerb said:
Both sounded like a waterfall, was just a lot of noise on the regulated supply prior to new caps.
Click to expand...

I’m about to go into my C-2x but I only have some background noise on my MC circuit. The MM is quite clean so I may have a different problem?
 
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