OK. It sounds
like your drive is basically working. What I'd
do at this point is look at the prints to see what should
drive the ready lamp. And then check back from the output
stage until you can find out why it's not being turned on. I
can dig out my prints and take a look too.
That's exactly what I intend to do :-) but I will first have
a look on the behaviour of the other two drives, while I'm at it.
OK, I've dug out my prints...
Firstly there's a useful flowchart of the drive operation at the start.
Watch out. it was wirtten for the RK06, and it sometimes talks about the
M7707 module which was replaced by the M7907 in the RK07.
In particular, the last couple of blocks in the spi-up sequence are :
Reset FWD FF and RTZ FF
Disable FWD servo
Enable Position Mode - Detent on next servo crossing
[B
After 3ms
Set Ready FF
Ready indicator lights
Set DSC FF and generate ATTN
Nwo, from the M79078 schemtic, the FWD LED and the RTZ LED are driven
directly from the flip-flops of those names. So the fact that they both
go off in your drive seems to indicate that the FWD and RTZ FFs are being
reset.
Now the operator control panel includes the drivers for the ready lamp.
Just to avoid looking for a fault in the wrong place, I'd monitor pin 6
(or 7) of E3 on that board. It should go high to turn on the ready lamp.
If it does, the problem is on the operator control panel board (possibly
E3, the bulb, associated tracks, etc)
It would appaera from a quick glance at the prints, that what actually
sets the ready FF is the signal SCR MOVE L at the output of E22e on the
M7907. This goes high when the heads are not seeking (intially when the
servo locks to cylinder 9). This should trigger E47a (74123) on the
M7705 board, which according to the prints is the 3ms delay. The output
of that clocks a 1 into E43a (7474) on the same board, whcih is the ready
flip-flop.
Now, what other signals could prevent this from happening?
Firstly, DC1 UNLD NEDS (1) L, but since the unload LED isn't coming on,
we can probably ignore this.
Then there are a couple of OFFSET control signals from sheet SC2 that og
into E49a on the M7705. The output of this gate should be high, I think
(check this).
And there's SA3 BET LIM (1) H, which could hld E47a reset. I am not sure
about that signal name, from what I can see it originates on sheet SC4,
and seems to detect when the head has got to the outer limit. You may
want to check this circuit too.
Anyway, some things to look at. When we find why the ready FF is not
being set, we can go back through the circuit some more.
-tony
