WSCART01@ULKYVX.BITNET (07/25/89)
Help! That sums up the mood i'm in. 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?) SIDENOTES: There was a little magnet along with, i guess, a magnetic sensor. What is this for? (Is the drive speed, chip controled?) I noticed spaces for 1 meg memory chips. (2 megs worth) Other than the holes being soder filled, and missing the corresponding compacitors; is the computer upgradeable to 4 megs just by putting in the 1 meg chips and the compasitors? (What type of compasitor should be used? Also what speed of meg chip is preferable, 120ns or 100ns?) The 68000 is soldered to the board. 4 empty sockets wait for tos 1.4 Nice open bus waits to be used. (Anyone know of anything that makes use of it? Kisses to Atari for haveing it an open bus.) Stuart Carter University of Louisville Physics Dept.
dlm@druwy.ATT.COM (Dan Moore) (07/27/89)
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