On Fri, 09 Feb 2007 09:49:43 GMT, "Arfa Daily"
wrote:
"James Sweet" wrote in message
news:CHRyh.3413$yI1.3217@trndny01...
Joachim Wunder wrote:
Hi there,
I have a garage door opener named "Liftboy SMD 3200" which was
installed into my garage back in 1990 (in Germany). I couldnīt get any
information about this garage door opener on the net. The motor
control PCB of it just failed this week. I suspect either any capacity
or the voltage regulator to be the culprit. Does anyone know the
manufacturer of the PCB shown under
http://img255.imageshack.us/img255/9023/cimg0094aq6.jpg ?
Unfortunately, the 40-pin PICīs type isnīt readable under the sticker
at all īcause its surface seems to have been scratched off under the
sticker by the manufacturer of the PCB. Yagh. Which PIC is it supposed
to be? There is a Quartz which reads "4.000 SUNNY 7624".
Moreover, the same applies to the 16-pin IC: Itīs surface seems to
have been treated by the manufacturer of the PCB, i.e. the exact type
has been completely scratched off on purpose as well. 
Is there any
way to find out which IC it might be?
Please advise.
TIA,
Joachim
The IC will have custom firmware on it so you won't be able to replace it.
Chances are unless the regulator has failed in a short circuit and caused
the voltage to rise, the chips are probably fine. Check to see if the
filter capacitor is shorted, I recently repaired an old Volkswagen ECU
that had a shorted electrolytic capacitor filtering the 5V output,
resulting in a dead car.
It seems to me that this is all getting a bit over-complicated. Why would a
simple device like this even need a micro-controller ? Some years back, it
was fairly common practice to put chips like this onto boards, that actually
did nothing. Literally just there for show to make the item look worth the
money that was being charged for it. Anyway, it seems that there is an
obvious transformer, reccies, and a smoothing cap. Is that where you are
measuring the 12v that you mentioned ? The very hot looking TO220 device
next to the smoothing cap is 99% certain a standard 3 pin monolithic
Yes, itīs a "L7805C-V". Well, I didnīt yet supply any 220V AC voltage
to the board in an offline test yet. I.e. after the garage door opener
failed, I didnīt dare yet to put on 220V~ again. Hmmm, is there any
valid means to test this "L7805C-V" offline with a 12V DC power
source?
regulator IC, and I would guess that it's almost certainly a 5v one, so do
It definitely is a 5v one!
you measure something like 12v, 0v, 5v on its pins ? If you do, do you have
a 'scope ? Can you measure any clock activity at that crystal ? Beyond that,
Unfortunately, I donīt have a scope, only a meter.
without a detailed knowledge of the functionality, and schematics, it's
pretty much impossible to come up with a valid test strategy, that's likely
to result in a repaired board.
Yes, I know. By the way, might he 16-pin IC a I2C maybe? If so, which
ones were commonly used to control an Intel 8748/8749 ?
Arfa
Thanks, Joachim