20 Sep
2011
20 Sep
'11
1:12 p.m.
Hi Christian,
Is the little red maintence switch in the right position? Was the
drive working earlier and just stopped? The quarterly PM usually helps
find this type of problem. Where are you located?
Paul
On Tue, Sep 20, 2011 at 2:41 PM, Christian Corti
<cc at informatik.uni-stuttgart.de> wrote:
Hi,
I'm trying to repair my RK05 drive. It seems that it doesn't find track 0
when loading the heads, thus moving the heads to the inner limit, forcing a
return-to-zero and starting all over again. I think the fault is on the
M7681 card (cylinder address and difference), the output of E16 pin 8 (CAD3
zero detect H) doesn't change, nor does the input on pin 10. And here comes
the problem: the M7681 isn't described in any DEC documentation I've found
so far (apart from the schematics), only the older M7702 card (the function
is practically the same, but they are completely different designs). The new
card contains several undocumented TTL ROMs (8223). The output of pin 6 of
E1 goes to the input pin 10 of E16, probably a difference==zero bit.
?So here comes my question: does anyone have a ROM listing of these ROMs,
especially of E1? I'd like to know what exactly that ROM is doing.
Christian