Yamaha C-50 Challenges

[toodletunes]

Picked up a Yamaha C-50 from the auction site. Upon putting it in the system, two gremlins reared their heads.

-There is both distortion (rather present) and a channel imbalance on both phono inputs. Verified impedance setting to be correct. Using a freestanding phono pre through a tape input the audio is clean and balanced.

-The input selectors are, for lack of a better word, finicky.

I typically test all functions before the de rigour thorough DeOxit treatment on newly acquired electronics. Do these flies in the ointment sound like some repeated applications might be effective?

BTW, I'm considered a menace with a digital multi meter ("Put the test leads down and step away from the DMM."). Let alone a soldering iron. Ouch.

 

[avionic]

Do these flies in the ointment sound like some repeated applications might be effective?

The input selectors are, for lack of a better word, finicky.

Likely needs disassembly and cleaning. Those 5 little orange relays are potentially in play. I usually replace all of them.

 

[avionic]

There is both distortion (rather present) and a channel imbalance on both phono inputs.

Phono select switch needs to be disassembled and cleaned ...

 

[avionic]

BTW there is a Yamaha forum..

 

[toodletunes]

Thank you, avionic. Will attempt the disassemble/clean and see where it gets things. Thinking if that doesn't resolve matters, it hits the tech's bench for relay transplants. Appreciate the heads up on the Yamaha forum. Will post there, also.

 

[avionic]

Appreciate the heads up on the Yamaha forum. Will post there, also.

Already taken care of that..

 

[toodletunes]

Not sure, avionic, if this or a PM would be best. Really need to address the volume pot issue on this C-50. Snagged the service manual, and precious little about it, directly. If I may, a few questions:

-Need the front panel come off to remove the volume pot? The top is off, currently.
-Does the potentiometer come off the board with a lift? Crowbar?
-Same for the pot's knob. Have given it a gentle pull. Get a bit more neanderthal?

All the above is prerequisite to the actual disassembly and cleaning. Have to do a successful potentiometerectomy first. Then, ideally, onward.

Much Obliged

 

[avionic]

-Same for the pot's knob. Have given it a gentle pull. Get a bit more neanderthal?

Usually 1.5 or 2 mm set screws.

 

[avionic]

Need the front panel come off to remove the volume pot?

Yes.. You will see the 2 setscrews for the knob and the main shaft hex nut that fastens volume control to the metal chassis.

 

[avionic]

-Does the potentiometer come off the board with a lift?

Needs to be de-soldered from the main board. 12 solder points..Main board will need to be loosened a bit to disengage solder pins from the PCB.

 

[toodletunes]

Thanks so much, avionic, for your detailed and generous response and direction. The set screws and hex nut are in my comfort zone. However, twelve solder points on a board such as this is, to put it mildly, a risky notion when factoring in my somewhat unrefined soldering skills. might be headed to someone's bench.

 

[avionic]

Pick up a piece of junk BPC to practice soldering and unsoldering.

 

[toodletunes]

Junk BP? There IS such a thing (no added charge for the smarty pants smirk)?

 

[avionic]

Junk BP?

BPC - black plastic crap --- cheap piece of junk with a circuit board to practice on..