Yamaha C-50 no input on Direct Disc.

[gary7]

Picked up a C-50 preamp. Has a Direct Disc MC switch and input that suppose to bypass other controls. The switch functions as it should. But no signal input. Anyone familiar and might know what's the issue might be?

 

[avionic]

Anyone familiar and might know what's the issue might be?

Yes and possibly Yes.

 

[avionic]

Disc Direct is phono only.. RY102 or RY104 could be fouled.
Personally I would replace all 5 of those relays with new pieces.

HB2E-DC24V

Exact replacements can be acquired on ebay. About 10 -13 USD a pop.

 

[avionic]

The switch functions as it should.

Do the input selector red LEDs dim when DISC DIRECT is depressed ?

 

[gary7]

Do the input selector red LEDs dim when DISC DIRECT is depressed ?

Yes, they do. And I hear a click.

 

[gary7]

Disc Direct is phono only.. RY102 or RY104 could be fouled.
Personally I would replace all 5 of those relays with new pieces.

HB2E-DC24V

Yes for a MC cart. Phono 1 & 2 work fine as MM & MC.

 

[gary7]

Well the Direct Disc switch is working, sort of. I'm using my SOTA with Monster MC cart. Got it to play, but the load switch has to be on MC, too. Thought it bypassed this switch. And, with the DD switch on, I can push the other input switches and it stays on the DD as it should, but if I move the load switch to MM, it cuts out. Also getting an intermittent hum. I can move the preamp or cables, the hum drops in and out. It did not have hum with my HK preamp or when plugged into ether Phono 1 or 2 on the C-50 without a ground wire. Going to take it apart again tomorrow and see if I missed something when I was deoxing & cleaning.

 

[avionic]

but if I move the load switch to MM, it cuts out

Dirty ( LOAD ) slide switch most likely. Requires disassembly !

I can move the preamp or cables, the hum drops in and out.

Possible cracked RCA jack solder connection or dirty RCA jack.

 

[avionic]

but the load switch has to be on MC, too. Thought it bypassed this switch

Service manual refers to DISC Direct in the schematic as as MC direct.

 

[gary7]

Pulled it last night. Flipped it and re-flowed the DD inputs. Cleaned all switches and inputs again. Hooked back up. No hum this time.

 

[avionic]

Missing audio clear up as well ?

 

[gary7]

Missing audio clear up as well ?

What it is doing is it will play DD if I have the load switch on MC. If I turn load switch to MM, the sound drops, but the DD lamp is still lit. Now with the DD switch on & the load switch to MC, I can push the other input switches and it stays on DD. But as I read in the OM, with DD switch on, it is supposed to disable those switches, or did I read it wrong? And not that good at reading schematics.

 

[gary7]

What I'm trying to figure out if I want to hook one MC to the DD input, can I hook and use another MC to the 1 or 2 Phono input and use it when the DD is switched off.

 

[avionic]

What I'm trying to figure out if I want to hook one MC to the DD input, can I hook and use another MC to the 1 or 2 Phono input and use it when the DD is switched off.

I think so..

 

[gary7]

Running my SOTA/Monster Alpha 1 MC thru the DD input. Damn good.