Aligning floppy drive heads

[llopis]

On EME150A to EME156, these grouped together on a connector (only mounted on EME150A)
On other, tests point all over on the PCB

Ah, perfect! I looked and looked and didn't find TP until you said that. Now I see they're all together :-) I'll check it out tomorrow. Thanks!

[llopis]

Don't mess with that ! It's the track 0 detector 
Forget the service manual, you need an alignment disk to follow the procedure, and these does not exist any-more.

I usually use a original CPM disk (or any other commercial disk) as reference, and RPM for moving the head.
1. You have to slightly unscrew the motor head so you can turn it a bit at a time, but not too loose.
2. turn the motor in one direction (less than a degree)
3. make the head move up-down and / or down/up to make sure the head position itself properly.
4. with the scope, probe the output of the head amplifier (I just can't remember where exactly it is ...)
5. repeat step 2-4 until you reach the maximum amplitude. If the amplitude decrease, turn the motor in the other direction.

OK, I'm finally getting around to doing this, and this step breakdown was super helpful. I wanted to check that things are sane before I start moving things around.


If I understand it correctly, since neither TP1 or TP2 are ground, I need to probe both and subtract them to get the output amplitude, right?
This is what I'm seeing when I do that. The amplitude of the result seems to be about 300 mV. Is that roughly correct?

[gerald]

If I understand it correctly, since neither TP1 or TP2 are ground, I need to probe both and subtract them to get the output amplitude, right?
This is what I'm seeing when I do that. The amplitude of the result seems to be about 300 mV. Is that roughly correct?

You're only interested in getting the max AC signal so only one of the test point is enough (use AC coupling).Now for the max amplitude, I just have no precise idea. I did not adjust a drive in the last 2 or 3 years 

[Bryce]

From what I remember, you should get about 60 to 80mV between either of the TP's and gnd. Make sure your GND flylead from the scope is as short as possible. At that voltage level you'll be picking up quite a bit of noise.


Bryce.