Yamaha YC-20 effects pedal required?

[waubain]

Hi Group,

I acquired a "non functioning" 1970Yamaha-20 (no pedal, no legs...who would have guessed). I was told the LED comes on when plugged in but not sound. I am not a technician, but am comfortable and respectful of electronics. I got a service manual and am trying to follow the schematics. It appears there are 24 volts out of the output jack to run a lamp/photocell pot in the effects/volume pedal.

I have not plugged it in yet, just getting acquainted with the electronics.

My question is if the effect/volume pedal is required to function? It seems like 24 volts is a lot for a line level out. although there appears to be a voltage divider that may drop the voltage to the jack to line level.

If there is not a pedal, can I just plug into the jack directly to an amplifier?

Thanks

[Drawbar Dave]

They have a light dependant resistor and bulb in the pedal hence the 24 v. You see the Yamaha pedal on eBay sometimes. I had the same setup on my Solina and isolated the voltage and then used a normal pedal with a pot until I found a Yamaha pedal. It should work without a pedal connected.

[waubain]

Dave, Thanks for the information. I finally got the time to open it up. The previous owner as some point made some modifications. A 3 prong power cord was added (a good thing), but the pedal output is now sent to a 5 pin connector using the old pedal chord. The original jack connector tip wire (red) is cut at the terminal end, and the connection to the new tip connector is from the 5 pin DIN. Attached some pics.

Anyway, have more investigating to do. Thanks again.




..... I jumper the red and white on the 5 pin DIM and she came to life. All keys and stops work, but some contacts need cleaning. A good day!

[Drawbar Dave]

Glad you got some sounds! The original Yamaha combo pedals I’ve used had a lead attached with a stereo 1/4 jack plug, so you’d want to have a stereo female 1/4 panel mount in place of the 5 pin. Some organs like my Farfisa Compact Duo used 5 pin din “midi style” connections for the swell pedal. These also had a bulb in them. Maybe a previous owner wanted to hack in a non Yamaha pedal.