On Fri, 09 Feb 2007 01:00:10 GMT, "David"
wrote:


"Joachim Wunder" wrote in message
.. .

Judging by the amount of heat that has been pouring off that regulator,
and
discolouring the board above, the first thing that I would be doing is
removing that chip that says " VOH " on it from its socket and cleaning
the
pins. What exactly is the board doing wrong ? Assuming that device is a
PIC,
in general, they are very reliable.

Arfa


Well, ok, cleaning the 16-pin IC´s pins will be easy, and I´ll do so,
of course. Well, from my first investigations the 40-pin PIC is very
likely to be an Intel 8748 or 8749. Question now is what current PIC
is still compatible to this old-fashioned one.

The whole board should control the 220V~ motor of the garage door
opener, but nothing happens no more. The board behaves like dead.
Reason might be a 25W bulb which blew off just before the board didn´t
show any reactions no more. The 25W bulb is connected in parallel to
the PCB´s power supply.

If indeed this is a PIC or some other type of microcontroller, you cannot
just replace it. It has to be programmed with the original code. Good luck
acquiring that since most manufacturers set a bit in the device to prevent
reading the program stored within.

Yes, I am aware of the fact that I would need a PIC programmer and a
new 8748 or 8749 PIC (I´m still not sure which one it really is).
Pretty good question where to still get such a component from, I
know,... is there any equivalent PIC which offers the same pin
assignment and code compatibility of a 8748/8749? I know, even I doubt
that, but I better ask in this group before giving up.


The failure of the 25 watt bulb may be a clue. A bulb can momentarily create
nearly a direct short when it fails. What voltage is this bulb? 220v or
something smaller?

220V AC, as we have in Germany.


David


Joachim