Tandon TM848-2 Floppy drive power

------------------Original Message: Date: Tue, 23 Jan 2007 11:23:32 -0500 From: "Kelly Leavitt" <kelly at catcorner.org> Subject: Tandon TM848-2 Floppy drive power To: <cctalk at classiccmp.org> Message-ID: <07028839E9A3744F87BEF27FF2CFF8E30B1494 at MEOW.catcorner.org> Content-Type: text/plain; charset="UTF-8" The drive in my Tandy Model 6000 has +5, +12 and +24 connected to it (pins 5, 4, and 1). The schematic in the service manual I have shows 4 as NC and a 7812 providing the 12v from the 24v line. The specs for the drive in the service manual do not mention +12 on pin 4 at all. The scematic at bitsavers isn't a lot of help. I don't have the drive here in front of me. Does anyone have one where they can verify the connections from the AMP power connector to see if pin 4 actually goes anywhere on theirs? -----------------Reply: The drive in front of me corresponds to the service manual, i.e.: AMP PCB P7 1 1 - +24V 2 2 - GND 3 3 - GND 6 4 - GND 5 5 - +5V 4 NC However, the schematic & PCB have a jumper position (LV) which bypasses the 12 V regulator, so presumably there was an option to omit the LM340T-12, C6 & R1 and connect +12 directly from pin 4 of the AMP connector to where R1 would be. Looks like there was also an option (on the schematic, not the drive) to use pin 4 (and/or pin 3) of the AMP connector to sense when a disk was inserted and turn power to the drive on/off. BTW, on the drive the fuse F1 is in the main +24V line, whereas the schematic shows it only in the branch going to the 12V regulator. Hope that's clearer than mud & helps. mike