🚀 go-pugleaf

in article <8907250426.AA12717@jade.berkeley.edu>, WSCART01@ULKYVX.BITNET says:
> I bought a mega2 about 4 months ago. (Yes, out of warrenty.) I've had some
> disk compatablitiy problems. Nothing big, but it seems that my RPM is a bit
> on the high end of the scale. I've adjusted drive speeds before, but I
> couldn't on the Mega2. I couldn't find a control pot for the motor. There
> was a small variable pot but it seemed to be hooked to the stepper moter.
> (I tried it anyway, but it didn't make any difference.) There was a bunch
> of resisters on the board, i'd hate to think that the speed is hard wired.
> Tell me is isn't so! (If it is, which one controls the speed?)

	Most of the better 3.5" drives use a phase lock loop to control
the drive RPM.  They are supposed to be calibrated at the factory (the
drive company's, not Atari's) and that is it.  Most of them do not have
any way to adjust the drive speed after they leave the factory.  These
are the best drives since they have very stable speeds.  It takes a lot
of extra drag (eg. pushing very hard on the disk media while spinning)
to make them change RPM.  But if they aren't correctly calibrated they
stink.

	Atari has started using some less expensive drives, belt driven
instead of direct drive, most of them do have adjustments for the drive
speed.

	You might try contacting the company that built the drive and
asking if (and how) the drive RPM can be adjusted.  Depending on which
company you may or may not get any cooperation.
	
>  There was a little magnet along with, i guess, a magnetic sensor. What is
> this for? (Is the drive speed, chip controled?)

	That is probably the drive speed sensor for the PLL.  If so then
there is probably nothing you can do to adjust the drive RPM.



				Dan Moore
				AT&T Bell Labs
				Denver
				dlm@druwy.ATT.COM