23 May
2012
23 May
'12
11:44 a.m.
Tony, I was expecting that kind of reply : ) I've
been lurking on the
list for long enough to know..
Unfortunately I don't have much spare time at the moment, I'm in the
middle of renovating my house, so these machines will have to wait a
while if I'm doing board level repairs (or any repairs for that
matter). Another issue is that I'm rather short of bench space, which
will be much better when the house is finished (and my collection of old
motor scooters is out of the way).
While you obviosuly did the right thing to rescue these machines, and
that could not have waited, I doubt that your life or livelihood depends
on having them working _now_.
These are great machines, and deserve to be treated properly, so what I
would do is do the simple PSU checks, etc and just see if they work, and
then put them aside, assembled, until you have fixed up the house and
have bench space. Then you can attack them properly.
It is a spare memory box for a 9820. It does not have
a complete set
of cards though, only has one each of blue, green, yellow, and orange.
RAM, memory data, memory address, memory timing in that order :-)
The HP9820 can take 2 RAM cards, and unlike the 9810, both RAM cards are
the same (red and blue handles). So if one of your 9820s has the same
memory box and only one RAM card, you can upgrade it. If not, it's a good
source of 1103 DRAMs (the RAM card contains 16 of them and not much else).
Note I said 'if ... same memory box;. The point being that there was a
field upgrade to the later type of RAM. This used 2102 SRAMs, 2K words to
a PCB. The memory boc was totally redeisnge,d the cotnrol logic was
simplified (no need to do refresh cycles, etc) and fitted onto 2 PCBs,
leavign sapce for 3 RAM PCBs. If you did this upgrade, you got a new
memory box, cotnrol cards and RAM cards, but moved the ROM boards
(red/brown and red/red) from the old box to the new one. I think you
replaced the 5V PSU board too, I would ahve to check.
I have never actually worked on this version of the machine, so I won't
be much help on the memeory system. But whtever you do, make sure you
dont swap boards between the 2 versions (I don't think they'd fit
anyway), since you will do a lot of damage.
-tony