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HELP WITH YAMAHA C-80 PRE AMP no sound!!

S

swansong04

Member
WELL , was so excited got my new to me Yamaha c-80 pre amp in the mail off of eBay .. powers up perfect looks brand new !!! hooked my m-80 up to it my turntable , my cd player and my computer and i have no sound on any of these inputs .. i am pulling my hair out with this problem !! not even any sound on the headphone jack !!! nothing !!! is there something i am missing ????
any info would be great..


Gary
 
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swansong04 said:
WELL , was so excited got my new to me Yamaha c-80 pre amp in the mail off of eBay .. powers up perfect looks brand new !!! hooked my m-80 up to it my turntable , my cd player and my computer and i have no sound on any of these inputs .. i am pulling my hair out with this problem !! not even any sound on the headphone jack !!! nothing !!! is there something i am missing ????
any info would be great..


Gary
Click to expand...

Mute button depressed ?
http://sportsbil.com/yamaha/c-80-om.pdf
 
If hookup is not the issue .Then I would suspect a power supply/power on mute circuit issue.
 
Are the M-80 input attenuation knobs fully clockwise?
 
avionic said:
If hookup is not the issue .Then I would suspect a power supply/power on mute circuit issue.
Click to expand...



damn!!! not what i wanted to hear !!!!!

is that a big deal to fix/ diagnosis ??
still a bit of a newbie with vintage audio but far from a newbie with a/v equipment ...
thanks again

Gary
 
if i crank the volume i can her just a vague signal through my headphones but just the slightest sound !!!!! argh !!
Click to expand...

power supply/power on mute circuit issue.
Click to expand...
Did you try the inverted output as well ?
 
swansong04 said:
damn!!! not what i wanted to hear !!!!!

is that a big deal to fix/ diagnosis ??
still a bit of a newbie with vintage audio but far from a newbie with a/v equipment ...
thanks again

Gary
Click to expand...

Can you read a schematic and use a multimeter?
 
avionic said:
Did you try the inverted output as well ?
Click to expand...

yup just tried that ... no go !!!! damn damn :thumbsdn:


ok , hooked my m-80 up to the rec output of my c-80 and put the cd player on aux inputs and the rec out switch on aux and now my m-80 works .. but no volume control on the c-80 have to adjust the volume with the gains on the m-80
 
cubby01 said:
Not a helpful question but did the previous owner say it was working fine?
Click to expand...
the ad reads that it works perfect except for a scratchy balance .. came in the original box and original owners manual .. he has good feedback and sell lots of vintage audio gear... i am try to get a hold of him now


Gary
 
Visually check solder connections in that circuit for cracked solder joints as well. Especially the two heatsink mounted regulators.They run real hot and thermally stress the solder connections.
 
swansong04 said:
the ad reads that it works perfect except for a scratchy balance .. came in the original box and original owners manual .. he has good feedback and sell lots of vintage audio gear... i am try to get a hold of him now


Gary
Click to expand...
hmmm ... My thought was if it was working fine with the previous owner then it's likely something your missing in setup or something that was affected in transit. But with Yamaha stuff you've certainly in good hands with Avionics's advice. (although I'll be happy when Halloween is over and he changes his avatar, ha! :D )
 
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avionic said:
http://www.hifiengine.com/manuals/yamaha/c-80.shtml

Look at R500 4.7 ohm fusible resistor in the power supply/mute circuit. Should have around 15.6 volts on both sides of this resistor.
Click to expand...


ok because i am an electrician and not a electronics guy when finding 15.6 volts on both sides of resistor r500 where do i put the common side of the meter ?? i assume is dc so i am looking for a negative ??

i found the r500 on the prints you linked me too now i will have to dive into it ..

thanks again for all your help
 
cubby01 said:
hmmm ... My thought was if it was working fine with the previous owner then it's likely something your missing in setup or something that was affected in transit. But with Yamaha stuff you've certainly in good hands with Avionics's advice. (although I'll be happy when Halloween is over and he changes his avatar, ha! :D )
Click to expand...

This is a typical failure in these models . Usually solder connections.Could have happened in shipping.Or have been and intermittant problem until now.
 
Black common (-) lead to a good chassis ground and probe voltages with the red (+) lead..Probe with red lead and meter in DC volts.Be very careful you don't inadvertantly short anything with a slip of the probe.If you don't have mini-grabbers,I would suggest some electrical tape wrapped around the probe tip leaving just the very end exposed.Or heatshrink tubing.
 
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