23 Aug
2011
23 Aug
'11
12:16 p.m.
In the -A, I
beleive, the 2 processors are on one PCB, there's a separate
PCB with the arbitration logic on it.
This does appear to be the case, at least from a simple visual
inspection. There is one PCB containing two large heatsinked units,
which I assume are the CPUs. The tape drive
mechansims are the same as those in the 9815 and 9825, and
suffer the smae problem of a decayed captsn. There are various web pages
giving repairs using things like heat-shrink sleeving or Citroen sleeve
seals.
Yeah, that's about what I figured. Am I correct in guessing that tapes
for these are pretty hard to find, or is there an easy to find equivalent? From what I remammeber the tape are not pre-formatted.
They;re the same
tapes as are used in the 9825, 9815, 85, etc. Not common but not
hard to
find eitehr. You cna use TU58 tapes, but this destroyes the clock trakcs
on said tapes makingthem useless for the original applciation in the DEC
drive. TU58s are not that common either.
Somewhere I read of a failry simple hardware mod (change a resistor o
nthe tape drive PCB I think to iuclrease the write current to use a
higher coercivity tape in the same type of cartridge. I've never tried it.
I am not sure the service manual is a lot of use
now. Certainly for the
-B it's a boardswapper guidewith little real inforamtion in it.
Well, at least since I have three of these machines to play with,
boardswapping is at least an option (though I know it's not your
favorite :)). I've done some basic testing of the power supplies and
they all appear to be working nominally, so at least those're good -- any preventative maintenance you'd recommend for
the supplies in these?
Alas I think you're right. The -B at least is a large and hevy machine,
and I asusem the -A is similar. Maybe one will turn up over here
(although a -C would be more interesting to me, I'd love tolook at that
colour video boardwith the 2903s on it).
-tony
Alas the only 90845 I have is a 0945B with the high-speed LPU. And while
I've produced as shcmatic of that, I can't produce them of machines I
don't own :-)
Well, I'd be happy to send you one of mine, but I'm guessing the
shipping across the pond would be prohibitive :).