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Yamaha C-60 Intermittent no Output to M-50 Amp

rickknight

rickknight

Active Member
I have a Yamaha C-60 Pre/Control amp connected to a Yamaha M-50 amp. The combo sounds great, when it's working. Sometimes when I turn everything on and select Phone or CD, or any other input, I get no sound to the M-50 or to the headphones. If I turn everything off and come back to it a few days later everything works perfectly. In fact it works perfectly about 70% of the time. Because I have no audio to the headphone jack I assume the problem is with C-60 and not the M-50. Has anyone else come across a similar problem with Yamaha C-60 or other Yamaha Pre amps? Any idea where to look to fix this?

Thanks,
Rick
 
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If you've done a thorough Deoxit job, then you may have some solder that needs to be reflowed. It's a common problem with Yamaha preamps from that time period, although it usually results in channel dropouts rather than both channels at once. I've read about another problem that is supposed to be common, but I'd try the above first.
 
Thanks Stereofanboy,

I have not hit it with deoxit yet. I picked the unit up a few years ago from a local used book/eclectica store for a song. It looked clean and had been gone over by a tech friend of the store owner. I don't at this point know how well it was cleaned, so I'll try and open it up this weekend. This unit is only a pre amp, but does it have a protection circuit like a main amp?

Thanks,
Rick
 
Do the red LED's light up ? Look over the soldered connections. Especially the two transistors that are mounted to large heatsinks. I usually reflow these solder connections reguardless. There is also a handful of copper buss strips that sometimes need to be reflowed as well.
 
Spot on Avionic! I took time last night to open the pre amp. At first I missed the transistors you were talking about, but when I did find them I discovered that all three solder joints on both transistors were cold. Re-soldered and then tested it while it was apart. Worked like a champ. Now while had the pre amp apart I did a very thorough deoxit job, took the front panel off, removed the selector switch board and the volume control board and hit everything. Put it all back together and now this pre amp really sounds great.

Thanks Avionic and Stereofanboy
 
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