Jim Cathey wrote:
Received a care package from Casey yesterday: his dead low-oil board.
Though the board got a little smashed in shipping (in a semi-padded
envelope), I expect a resoldering to cure it, if it hasn't been
destroyed in its travels. The capacitor that sets the oscillator
frequency to 256 Hz was very poorly soldered and was even loose in its
holes. Without the capacitor I think the oscillator will run much
faster than it should, negating the time-delay function of the board.
(Its only function, in fact.) The rest of the soldering on the board
looked quite good.
On the bench the oscillator ran at 271 Hz (nominal 256 Hz), but when I
wiggled the capacitor the frequency jumped up to nearly 600 kHz,
approximately 2000 times normal, but well within silicon logic's
ability to operate. This would reduce the light's time delay from 60
seconds to 27 milliseconds, effectively removing the delay altogether.
I rigged a light to the board on the bench, and with the oscillator
running fast the board worked as one would expect with nearly a zero
delay. Wiggling the capacitor until it made contact again restored
proper operation of the board: it took about two seconds of grounding
the input to make the light go off, and about sixty seconds of the
input open to make the light go on again. Success!
These things look repairable to me. I think I may add it to the
shingle.
First class!
Marshall
--
Marshall Booth (who doesn't respond to unsigned questions)
"der Dieseling Doktor" [EMAIL PROTECTED]
'87 300TD 182Kmi, '85 190D 2.0 161Kmi, '87 190D 2.5 turbo 237kmi, '84
190D 2.2 229Kmi (retired)
