Yamaha C-4 Phono Preamp Schematic

[gridleak99]

Would anyone be able to share the schematic for a
Yamaha C-4 phono preamp section?
HiFi Engine is no longer allowing new members to register.
Any help, greatly appreciated.....

 

[avionic]

Don't get any better than this..

Yamaha C-4 Service Manual, Analog Alley Manuals

 

[avionic]

 

[avionic]

 

[gridleak99]

Many thanks, avionic, for sharing.
Using an ancient Nakamichi T-100 signal generator
as a source cranked down to 5mv, the right channel MM inputs
are not working. If anyone has experienced
the same problem and has some pearls of wisdom, I'm all ears.

-gl99

 

[avionic]

Many thanks, avionic, for sharing.
Using an ancient Nakamichi T-100 signal generator
as a source cranked down to 5mv, the right channel MM inputs
are not working. If anyone has experienced
the same problem and has some pearls of wisdom, I'm all ears.

-gl99

View attachment 3215338

Most likely a dirty switch in the audio path. Either PHONO select switch , Input select switch or Cartridge load switch. Would be my first suspect's.

 

[avionic]

Using an ancient Nakamichi T-100 signal generator
as a source cranked down to 5mv, the right channel MM inputs

Ideally you want a reverse RIAA circuit between the Nak and the C-4.

Reverse RIAA

ESP Project Pages - Reverse RIAA Equaliser

sound-au.com

 

[gridleak99]

Many thanks to Avionic and Mikehd for your help with my C-4 problems.

As it turns out, the phono preamp dead channel was due to extreme oxidation on the
Phono selector switch wafers and the impedance matching slide switches.
It was necessary to unsolder and remove all 3 components to manually remove
the oxide deposits from the switch contacts. Once cleaned, I coated the contacts
with Caig Labs product before assembly.