Does anyone have a schematic or know where to find one online for either of these two DISK II alternate brand vintage floppy drives? Looking for schematic for MITAC Model AD-1 and/or SHUGART Model 390 vintage versions of the Apple Disk II 5 1/4" floppy disk drives.
In particular, I need the MITAC AD-1 schematic as I own two of them. I did one in by placing a new slightly longer cable on the wrong way the other day, blowing up the 74LS125. I mean it was literally in pieces. All the ICs in this beast are soldered in. That makes repairing even more tedious. And it has TEN (10) IC chips, all soldered in, instead of the only FOUR (4) ICs in the Apple Disk II drives, which for mine those ICs are all on sockets. Which makes repair of the Apple Disk II drives easy, relatively.
I desoldered the 74LS125 chip today and put in a 14 pin socket and plugged in a new 125 chip. But it still don't work. So more damage was done.
Without a schematic my only recourse is comparing voltages and signals on the remaining good MITAC Model AD-1 to the bad one. That and circuit tracing by vision and hand. A schematic would make the troubleshooting and fix so much easier. Plus having a good schematic for equipment you own and maintain in one's library is always a good idea. Especially as more and more years go by re these vintage drives.
I've all ready ordered a complete set of replacement ICs (those that I could still find as available) of the 10 IC chips in the MITAC.
Here is a listing on eBay of someone who is selling one of the clone drives.
Based on this fellow selling this he must believe the MITAC AD-1 and the SHUGART 390 are virtually the same thing. So I'm of the mind that the circuitry may be much more similar in these two 3rd party suppliers of Apple floppy drives, than they are to the DISK II drives which have only 4 chips. Maybe one company made both and sold it private label under the other brand name.
But I don't want to buy another MITAC aka SHUGART, or vice-versa. I want to fix mine. And I will. But a schematic would make it so much easier.
I googled tonight and could not find a schematic for any of those model numbers or brands. So, if anyone has one, let me know and we can arrange to get a copy. Or if you have a link to one, post it in a reply.
Thanks in advance if any of you can help with this repair and troubleshooting documentation item.