ELKA 88 Piano restore- questions and documentation of

[jwin615]

Not sure which subforum this belong in. Nice if needed.
So, I picked up an ELKA 88 (electric) piano locally for 5 packs of Marlboros and a 40oz.

Pretty cool piece. I don't have schematics, unfortunately. Each key makes electrical contact via a spring across the top board. I haven't dug into the ICs, and hope not to.

So, it has issues. Was told it didn't power on and power cable was cut. I'm proceeding with caution as cutting a power cable in some industries is a manner of (lazily)decommissioning dangerous equipment.

Starting with the power section, There is a step down transformer followed by dual rail power sections.
Rectifier, diode, and a pair of caps and resistors with an adjustment pot. At first I thought the caps were bad but the worst one(1mF/1000uF) is about 17% high at 1171uF. So I'm content attempting to power it up like that but ultimately will recap.
Each of these two DC conversion sections had a .5A fuse underneath that was blown. The mains fuse was not.

Now into the funny stuff/questions.
1)this unit only has 2 wire power. With the rectifier cards removed, measuring across the hot and neutral input, togling the power switch appears to short hot to neutral?
There's no diode in path.
I'm guessing that due to the step down transformer but let me know if I'm missing something important.
2) what the advisable way to ground something made of wood with no chasis?
I was thinking maybe just going straight to the sleeve of the output.

Have to find my fuses or buy some so no power hitting it tonight.

 

[Bricksnbeatles]

Very cool! I've always been really into those early electronic keyboard instruments. Missed out on a fantastic deal for an RMI Electra Piano (like Ron Mael used in Sparks in the 70s) for $100 on craiglist last summer by just a half hour, and saw it relisted by the guy that beat me to it for $1,200 the next day lol

As far as both schematics and advise on the grounding goes, I'd look for some electric piano restoration forums– I know there are plenty of facebook groups for just that. While this isn't an electromechanical keyboard instrument in the sense that a Rhodes, Wurlitzer, Pianet, Clavinet, or CP-80 is, most of the people into restoring those will also have experience restoring these types of instruments too. Many of them were made and white-labeled under many, many different brands depending on the market they were in, so there's a good chance that someone will have a schematic for this exact circuit, just not labeled as being the ELKA brand. Good luck, and be sure to share more of the journey! Can't wait to see how it turns out in the end!

 

[SillyOctpuss]

That's super cool. I've had a quick look and was able to find this schematic. Not sure if it's the right one or not.

Edit: no I'm an idiot, that's completely wrong.

 

[Coda]

All pianos are supposed to come with a jar for bread…