I bought my C4 brand new when I was an undergrad. At first I mated it with a Carver Cube, which I still have. Later is was mated with an Adcom 555II. It has been sitting unused for 20+ years and I am considering a repair/refresh. I think it could be a rewarding project, but I'd need to buy some tools, watch some videos, et cetera. Alternatively, I could try to have it professionally done. I would only use it with the Adcom and my Technics TT which has also been sitting. If I get it working well, I might even buy a new TT and get back into vinyl. Is a repair/refurb project too much for a beginner? I have some electronics/EE in my background but I have not worked on PCBs, et cetera. Thoughts?
Yamaha C4 Pre-Amp: Worth Refreshing/Repairing?
- Thread starter mahler9th
- Start date
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No, not really.
One of the easiest Yamaha pre-amps to work on. Not at all densely packed. Nor hard to work on.
OP mahler9th - Welcome aboard mahler.
Do and AK search. There are probably dozens of rebuild threads on the C-4. With hundreds of my own posts.
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Just in case. I have had dozens of C-4's across my bench. Presently finishing up one on the bench now.
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Thanks very much for the input. I recall connecting with Avionic previously about this unit, which holds a very, very special place in my heart. Thanks so much for the encouragement, knowledge, experience and expertise. I have popped the top cover and the cover over the power transformer. Very dusty! Plugged it in for the first time in... 10-20 years. No lights illuminate.
Check and see if it works regardless of lamps. The C-4 I have on the bench now had 3 burnt out lamps.
In a quiet room. Place your ear close to the large rear circuit board next to the transformer. Listen for a very faint " tink " sound from the reed relay switches a second or 2 after powering on.
In a quiet room. Place your ear close to the large rear circuit board next to the transformer. Listen for a very faint " tink " sound from the reed relay switches a second or 2 after powering on.
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I plugged it in and hit the power button. I cannot hear a relay click, but there is an audible noise.. a kind of buzzing sound. Then a few seconds latter another buzzing sound starts-- it has a higher frequency. I popped off the bottom cover and the PCB topsides actually look pretty dang good. Flipped her over. At least some of the buzzing sound on power up is coming from the transformer.
I ran audio from Iphone into both aux and tuner inputs, and used some sr60 headphones. All I got was buzz/hum. No change in sound level with headphone or volume pots. Cleaned the bottoms of the boards with chip brush and acetone, and I am cleaning the contacts. I don't have a service manual. Most of my experience with schematics in the last 25 years has been related to my racing hobby. I think that can help. I have the original brochure and user manual which has a schematic.
The first thing we need to do is to verify DC power supply voltages.
Highly recommend. Don't get any better.
Highly recommend. Don't get any better.
Ok. Some cleaning and disassembly completed. I touched one of the 470 caps on the power board and it was loose. legs just broke off. The glue is deteriorated underneath all of them so I think I need to remove all three, do some cleaning and then replace them. I will be getting an iron and desoldering tool in the next few days. I wonder if it makes sense to buy a recap kit? Any opinions? I think I want to clean and then get it working first, but I reckon a recap will be in order.
I make my own kits. I don't have much faith with the available ebay selections. You wanted my opinion. There it is.
2 each.
Probably need one of these as well.
This will cover the 3 biggins.
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Concur
Practice on a piece of junk before the C-4. If your solder techniques are a little rusty.
I am profoundly grateful! When I was in HS I somehow got into all of this-- perhaps my gymnastics team coach sophomore year. He was an ex-marine and loved Yamaha receivers, which I could not afford. He thought highly of Onkyo too. I first bought an all in one system. Then an Onkyo receiver and a Pioneer fully manual TT and a Sankyo cassette deck. Cannot remember the speakers. There were only 2-3 high end audio stores in my town... I eventually got a part time job in one. I climbed the ladder a bit-- bought a 717 and an Onyko tuner and an SLQ2. Then somewhere in there I bought an M400 (early adopter) and the C4. I could barely afford any of this, but I was eager and determined. Ran Audio Analyst speakers. Right after HS I got a summer engineering job at the HQ of GE Healthcare and was assigned to systems engineering. Learned Ohm's law! Right before college I saw Animal House and got a call from D.C.from one of my roommates to be. His HS classmates included Teddy Kennedy and Jeb Magruder's son. His HS was about $4-5k per year in the late 70's. But he did not have a stereo and wanted to know if I had one. Of all the pieces I coveted and eventually got my hands on, the C4 is still somehow special. I am hopeful I can accomplish its resurrection. If I do, the first record I will listen to is Mahler 9th/Von Karajan. Thanks for the help and support!
I don't have any soldering skills, but I aim to get there. I will find something to work on. Maybe my 1978 GE alarm clock/radio.... but it's still working. Perhaps a trip to Goodwill!
I don't have any soldering skills, but I aim to get there. I will find something to work on. Maybe my 1978 GE alarm clock/radio.... but it's still working. Perhaps a trip to Goodwill!
