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C-70 powers up but no sound

mr_RBG

mr_RBG

Well-Known Member
I bought c-70, m-70 from ebay and the seller told that everything was in working order. I do believe him because it was packed good and he offered me a total refund! However, neither of them does not work. :( Let me start from C-70.

It lights up, magnetic selectors sometimes do not switch(never liked them), but after couple of iterations you con chose a right sours. BUT! there is no sound from it from any sources. More correct, if I increase volume to the max I can hear weak, tiny sound from my speakers. I've cleaned everything, mute button is off(however if I press it, it does not affect the sound at all).
I was found on the forum couple of posts with sort of similar problems but for C-80 http://www.audiokarma.org/forums/showthread.php?t=325543 , http://www.audiokarma.org/forums/showthread.php?t=309923&highlight=yamaha but I just can not draw a parallel with C-80 and C-70 schematics. Another thing which can help: When was cleaning the volume pot(after I plugged it first) a plastic container(you should know what i am talking about) sort of felt apart after I unscrewed two screws on its back, but it looked that it is just a case and the pot by itself is ok.

I would really appreciate any help, please. I was thinking to recap it, but Avionic(thank him a lot!) told me that it is betted ti locate and fix this problem which is(i agree now) true. Thank you guys!
 
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Having you tried switching your interconnect to the invert set of outputs? Have you tried pushing the high off/10khz switch on and off? How about the stereo/mono switch?

What are the symptoms from the M-70?

Do you have a receiver with main in/ pre outs that you can use to help decide which piece is at fault?
 
I tried all the switches and selectors, inverse as well. I did not try headphones cause I do not have any :). No no no, I am connecting the C-70 to my old perfectly working M-50, so now it is the pre diagnostics for me.
 
Make sure the disc direct is OFF. Mute off, Tone off, etc. No selector button lights lit except the desired source.

If it's a world model, make sure the voltage is set right.

Completely lost me on the "plastic container."
 
yep checked all, 120V. Soldered almost all soldering connections...
brutal, sorry about my stream of consciousness :)
I was talking about C-70 volume pot in a plastic casing. There two screws on the back of it which hold this pot or casing(do not know) together.
 
First..Need to verify that the power supply is working correctly.Then verify that the power on mute circuitry is functioning correctly.Then verify that the power supply voltages are getting to there correct destinations.
 
Thanks, Avionic, sorry for asking, but what is the best way to check the power supply? Sorry, I do not have much experience in diagnostics.
 
A multimeter and a servicemanual ie. schematic..Or a find a good tech willing and able to do the job.
 
Can anybody briefly explain me how this mute switch works? As I understand its operation is different from input source selector.

BTW, is C-70 schematics much worse than C-80, or its only for a newbie?
 
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