Matti Adolfsen wrote:
Fred McKenzie wrote:
My bet is the processor is still OK and repairing the regulator(s) will
bring it back.

That's what I'm hoping. Can you advise me on how to test the
regulator(s)? (I'm not even sure which one it is.)

I don't see one leaping out at me in your photo. As I recall, the 78L05
is about the size of a small plastic transistor.

You're right, it's too dark and receded to see. I've bent the two
components back a bit and scanned it closer:

http://img53.imageshack.us/img53/766...sistorsuz9.gif

The one to the left is marked "8054 HN 3C31". The one to the right is
marked "S78L 05ACZ 326"

I don't know how to test if the 78L05 is good or not. If it is bad,
I'm guessing that an electronics or surplus store would have them
right?


Find the 80C51 data to see which are the power pins, and trace the plus
lead to see what feeds it. Similarly, trace the power connector pins to
see where they go. They should meet at the 78L05.

I've checked the datasheet for the pinout:

http://img245.imageshack.us/img245/2033/pinoutuh0.gif

If you mean the VCC, it is connected on the component side and goes all
the way around to connect to the 78L05 (on the Input pin).


Look at:
http://img378.imageshack.us/img378/4...erfrontbo8.png

The upper right corner, above the jack, left to the 2 electrolytic
capacitors, there is one transistor-like (TO-92 case) component. it's
exactly where the positive lead (as seen in the solder-side photo of the
unit) coming from the DC jack ends.

There's also another component between the two capacitors. You can see
it in the close up picture above. Is that the one you mean? The one
on the left is an "8054 HN 3C31" which an Internet search brings up
almost nothing for, except the brief in which N Cook mentioned above,
stating that it was "intriguing".


--
Alec S.