8 Apr
2004
8 Apr
'04
10:37 a.m.
In message <m1BBLYF-000JAXC@p850ug1>
ard(a)p850ug1.demon.co.uk (Tony Duell) wrote:
Reminds me of the time a system manager at a place I
was working ordered
a failed servoid off the site. He wanted to replace every PCB in some
expensive piece of equipment because they all failed diagnositcs. I'd
just turned up, slapped a meter on the 5V line and found it was sitting
at 4.2V....
I've seen that happen. I (once) tried to repair a DIY speech
synthesiser; it
was suffering from the standard "it worked one minute and now it's dead"
problem. Vcc was at 2.1V (it was supposed to be 5V +/- 5%). I pulled the
SPO256 and powered up without it and the Vcc came up to 5V. Replaced the '256
and the Vcc plummeted again. Turns out there was a solder whisker on the
board, between a Vcc track and a GND track. Pushing the chip in flexed a
track slightly and moved the whisker into place over the tracks - removing
the chip allowed the whisker to move back and short the power bus. That
whisker took me a good half hour to track down - it was thinner than a strand
of wire-wrap wire. Of course, after I fixed the synth, I leaned over to plug
the interface connector in... and shorted out the PSU's output connector.
That did plenty of damage to the PSU, which still needs rebuilding. *sigh*
OTOH, I've still got a few SPO256es - all working. I just need some 3.12MHz
crystals for them. No, the SPO256es are not for sale :)
On saturday and Sunday They do no work at all
So It was on a Monday morning that the DEC man came to call
Very good - thanks.
Later.
--
Phil. | Acorn Risc PC600 Mk3, SA202, 64MB, 6GB,
philpem(a)dsl.pipex.com | ViewFinder, 10BaseT Ethernet, 2-slice,
http://www.philpem.dsl.pipex.com/ | 48xCD, ARCINv6c IDE, SCSI
... I am not young enough to know everything.