13 Feb
2011
13 Feb
'11
11:47 p.m.
Found those capacitors. Yes, they were indeed the trio that were clustered
together. All the -ve sides clustered together, and the +ve wired to a
motor output connection just as you said.
I spent tonight extracting the IC and the capactors. It went surprisingly
smoothly considering this is probably the smallest circuit board I've worked
on in terms of closeness of tracks.
Now to just wait until the ICs arrive from Hong Kong. I hope it's not by
slow boat. I've ordered and paid for the ICs but have yet to hear any kind
of acknowledgement apart from the standard paypal reciept.
I've also bought an X/Profile emulator. Luckily I've managed to sell one
of my Osborne 1s for $340 NZ (about $255US) to help part-pay for it!
So, here's hoping BOTH Lisas will be up and running 100% soon!. An ominous
sign in the Lisa 2 though. Yesterday it would just suddenly switch off I
was testing this drive. A little jiggling and waiting a while, then a
switch on and it would suddenly go again. Could be something loose, or
could be the PSU starting to give up the ghost. I have a spare working (I
think) PSU, so I might have to call that into service....or attempt a repair
if that's indeed the problem.
Maintence/repair is an ongoing process with this old iron isn't it.
Terry
Take a look at one of those HP drive schermatics I
mentioned. If you are
working from one of 'my' schematics, oyu want ot look at the sheet
entitled 'Sony Floppy Drive Spindle Motor Sheet (3)'. You'll see the
TA7259 chip. Connected to the inputs are the 3 hall devices H1-H3.
Connected ot the outpus are the 3 motor windings -- notice how the other
end of these windings are all linked together, but go nowhere else --
that's the 'star' (or 'wye') configuration I was talking about. And
just
to the left of the widnigns are 3 capacitors C11, C12, C13 wired in
another star circuit.
I have no idea what the capacitors will be labelled on your PCB. They are
likely to be a simular value. See if you can find 3 cpaacitors, arounf
10uF each, with the +ve side wired to a motor output connection on the
chip and the 3 -ve sides all linked together. It might be the 3
capacitors cludered just to the right of the chip in the photo, it might
not. You cna use the resistance range of your multimeter to check what is
connected to what, of course.
Alas without the PCB in front of me (and thus being able to trace
connections) I don;t think I cna be more definite.
-tony
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