But I woul
still check it. See if tyhe motor speed feedback signal looks
sensible too while you're in there..
I believe that's fine. By my reading, the drive would not come ready if
there were a servo lock problem.
You are problably right. On the other hand you should rememebr uyou've
not actually checked it just in case you end up not being able to find
anything wrong. At which point you check all that it 'bovisouly correct' :-)
And also, of course ,look at the read data
signal. Does it look senesible?
I've poked around a bit with a scope. The base clock signals mentioned in
the troubleshooting section of the manual are present, shaped correctly,
but the periodicity is exactly 2x what's printed there. This is a tough
Since yours is an earlier drive, it might well have a lower data density
which could imply slower data clocks.
call, though. The manual is for a different (and I
believe later) drive
model, so that difference might be as expected. It's also possible that
it's a typo. If the period was too small, I'd suspect a bad latch in the
clock divider. But, _slower_? It's hard to see what type of failure mode
would cause that, but perhaps I'm missing the obvious.
For the moment I'd not worry about it. But again, rememebr the oddity.
The index and sector pulses appear to be right on the money.
OK, so the problem is not there.
If I look at the output of the analog section, I can see what looks to be
reasonable read data. Unfortunately, from this point on there are
significant differences between the bitsavers doc and this drive. The
board layout is very different on mine and it has fewer gate array chips.
The manual suggests that the clock separator PLL is in the gate array,
while mine has a DIP MC4044 PLL serving that function. I admit to being a
bit fuzzy on how this stage operates (not an EE by background).
What do you get at the output of this stage? Do you get
reasonable-looking data and clock signals?
If you have fewer gate arrays and more standard chips, it actually makes
life easier because you can probably get data sheets on them. The MC4044
is a well-known device that somebody must have the data sheets for.
Oh, and for the record I'm not an EE either :-)
I really do wonder if the problem is in the controller. Do you have any
documetation on that? Scheamtics?
-tony