12 Jun
2007
12 Jun
'07
2:36 p.m.
Anyway, from what I remeber, the controller card is
based round a 6802
processor [1]. The actual disk contorller chip, anohter 40 pin device, is
made by Fujitsu, and has the same pinout as the 1793 _apart from being
+5V supply only_.
[1] If you've got chips marked with the HP house codes (1820-xxxx
numbers, maybe soem 1818-xxxx ones), let me know what they are and I can
see if I can find the standard equivalents.
Many chips on my controller have only HP house codes.
In particular, there are three 40 pin chips, with codes: 1820-2099, MB8866
(this has an "F" as logo, may be it's Fujitsu or Fairchild, I don't
know),
and an Intel D8291A.
Then there are four smaller chips (24 pins? I didn't count them...) marked:
1818-1834 and 1818-1835 (these are on sockets: may be they are roms?), and
two 1818-0701.
Then, the smallest chips (14-18 pins) with hp house codes are:
1820-2075
1826-0210
1820-1197
1820-1216
1820-1202
1820-1112
1820-1422
1820-2058
1820-0325.
Others are standard ttl chips, with both hp house code and standard ttl
code.
The controller board code is 82901-66503 REV. B
That mioght be enough to get you started. Grab a 1793
data sheet and
check the clocks at the pins of the disk controller. There is probably a
proper procedure for adjusting the free-running requency of the data
separate VCO, but at this point, what you want to do is see (a) is there
a read clock and (b) is it possibly a sane frequency.
I'll do it.
I can't remember much abotu the PSU in this unit.
IIRC there is a
seaprate PSU PCB (and presumably you can check the outputs of that quite
easily). It's quite possible the VCO circuit needs a -ve supply line.
This might come from the main PSU, but on at least one HP controller, it
was producaed by a charge pump circuit clocked from a divided-down
version of a master clock. That might be worth looking for and checking.
I've checked almost all points in the circuit, and I didn't find any -Ve
supply. Also, PSU only gives +5 and +12 volt.
Thank you very much.
Roberto