13 Nov
2007
13 Nov
'07
7:04 p.m.
I've seen bad 1771s out of the box (WD was not
allways a qualaity house)
but I've never seeen one fail in service excluding overvoltage or reverse
polairty.
I have, or at least I think I have. A friend had an RML380Z machine with
disk problems, and after a bit of troubleshooting, we traced it to the
1771 chip. I had _one_ spare at the time which I gave him, AFAIK the
machine is still running 10 years on.
Now obvioulsly I can't be sure there wasn't a spike on one of the PSU
rails that killed the old chip, but that was the only chip in the machine
to fail, and the 380Z PSU is a pretty simple thing full of 3-terminal
regulators, not known for playing up.
I've certainly had 1793s fail in my TRS-80 Model 3. One time it
intermittantly didn't prrduce DRQs, so the data register was not loaded
with the next byte by the software. The result was bytes being repeated
in a secotr. Ouch!.A text file might contain 'Hellllllllllllllo World'
for example.
One little nasty. The 1771 has a basic ability to do
data seperation.
I havent' looked at a tarbel board in a very long time but I do hope
that they didn't do the TRS80 save a buck trick and try to use that
internal seperator, it does NOT work. It has zero jitter tolerence.
Strange. I used an unmodified TRS-80 Model 1 EI for years and never had
any problems with the disk side of things. And that used the internal
data separateor of the 1771 IIRC.
-tony