13 Feb
2011
13 Feb
'11
8:58 a.m.
I am talking about the motor PCB end. 7 of the
wires are soldered to the
PCB in a row of 3 and a row of 4 IIRC. I couldn't see any sign of that
white wire on your photos of the top of the motor PCB, so I am wondering
what happens to it. Is it soldered to some point on the underside (solder
side) of the motor PCB, if so, where.
In this drive it seems to be a row of 3 and a row of 5 rather than 4. The white wire is can be seen in that set of 3 of the left
part of the board in
this photo.
http://www.classic-computers.org.nz/temp/2011-02-14-400k-sony-motor-circuit…
Firstly, I meant 'Star (Wye)' not 'start'. Perhaps I have confused you
with that typo.
The terms come from 3-phase electrical engineering (which is quite cloe
towhat this motor uses intenrally). If you have 3 wires (in this case the
3 motor outputs of the chip) and 3 deices to connect between them, the 2
ways it's normally doneare to connec the 3 devies in a triangle (so one
goes between wires 1 and 2m one between 2 and 3, one between 3 and 1) --
this is called 'Delta' connection (the capitcla Greek letter Delta is a
triangle) or to conenct the devices one from each wire to a common point
(that goes nowhere else in this case). That's called 'Star' connection in
the UK, and, I beleive 'Wye' connection (becuase it looks like a 'Y') in
the States. I don't know what it's normally claled in New Zealand.#
There are 3 capacitors connected in a start
(`Wye') to the motor winding
connections. Ifthey're defective, the back emf from the windings can
damage the chip.
Tony ..."connected in a start (`Wye') to the motor winding connections."
I'm not sure what you mean by this. What is a "wye"? Pardon my ignorance
in these matters. I realise we had no circuit diagram for this
particular drive, but would
those capacitors be obvious from their positions on the board? Can you see
them in the photo under the link?
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