21 Jan
2008
21 Jan
'08
11:05 p.m.
Hi,
I've been trying to create a working Sony MPF50W (as found in the HP1650B
Is this one of the half-height units using many of the same parts as an
Apple 800K drive? In other words similar to the drive used in the HP9114B? sensor.
I'm reasonably sure that the heads are okay, they show continuity
on some of the pins, but I'm not 100% certain that is what I should be
If this is one of the drives covered in 'my' diagrams, I'll have shown
the head connections there. A head winding will test as a very low
resistance (dead short) on a meter. Just about the only thing that's not
connected to anything lese is the screen (shield) The full-height Sony drives have the head switching
diodes on the
flexiprint to the heads, which might confuse your tests. The half-height
ones have sepearate head tails from each head ans the swtiching diodes on
the main PCB.
In fact the swtiching diodes in ising IC102, the read/write ASIC
expecting. I can't find any obvious sources
of information on where to
probe to see useful signals from the heads or find any procedure to align
If this is the drive I think it is, the analogue circuity is in one big
ASIC. There's an LC filter circuit hung off that. looking at 2
'equivalent' pins of that with a differential-input 'scope will show the
head signal. from the marked corner as usual), the're the ends
of R149.
The normal way to alignt the track 0 sensor involves the euse of a drive
exerchiser. What you do is move the sensor right out (to prevent it
stopping theh eads from stepping out when they get to what thr drive
things is track 0,), then, with 'standard' formatted disk in the drive,
step out until the signal is lost (that's one cylinder past track 0),
step in once, and move the sensor in until it just triggers. Then make
sure that the track0 signal is asserted on track 0 and not on track 1.
You can test the Track0 sensor output on the '00' test point. That's the
'top' (non-earthed) end of R128, or the middle pin of CN104 (bottom right
corner of sheet 2 of the drive schematics).
-tony