Yes, it's me again. Bear with me for a moment: I think I found
the problem.

The EKB is Yamaha PSR-12, about 20 years old. I can leave it powered
for a long time, no problem. Play it for 30-90 seconds and it
freezes up, keys don't work.

It has 4 boards:

1.) "1684 PN1" - large board with markings for voicings
2.) "1684 PN2" - large board with markings for effects, etc
3.) Power Supply - from batteries or converter
4.) Switch - main power switch and master volume

1.) connects to 3.) via a pair of very long wires. The connector
(or concentrator or ?) that mounts on 1.) looked funny, so
I calibrated my multimeter for ohms and tested for continuity
between solder points on the 2 boards. One wire measured about
5k ohms resistance, the other about 4k ohms. I *think* I
measured 5v between these 2 some days ago (at 3.)).

I powered the unit and played it until it froze, then jiggled
the connection at 1.). It unfroze momentarily. I jiggled some
more, again it unfroze momentarily.

I'm pretty sure I've found the problem. Hopefully now to assess
how it might be repaired.

The connector (or concentrator or ?) on 1.) is just a little white
3-D rectangle. The 2 wires stick thru the board and are soldered
on the opposite side (like beau coup other connections on the unit):

http://www.flickr.com/photos/pudding_man/

(Disregard all the dawgs) :-)

Does this sound/look like a broken solder joint where the wire
sticks thru the board? Other possibilities?

What might be involved in a repair? Possibly just re-solder??

Any/all help much appreciated.

Cheers,
Puddin'

"Well, there's two trains runnin'.
Ain't neither one goin' my way.
One run at midnight,
the other run just before day."
- from "Still A Fool", Muddy Waters, maybe 1949