Rick Thornquist Posted March 7, 2015 Share Posted March 7, 2015 I just bought an SF314 Floppy Drive for my 1040STf. I plugged it in, booted the machine up, and was ready to revel in the glory of two floppy drives. Unfortunately, there was no reveling. When I tried to read from the drive, the LED just blinked for a split second and then I got the message "Drive B: is not responding...". D'oh! I'm far from an electronics wizard, but I can use a multimeter (barely). I checked the voltages coming in from the power supply to the back of the drive case: 13.18V and 5.02V (I realize that I may be getting spurious readings by checking the power supply without a load). I then checked the power connector going into the drive mechanisms itself: 8.80V and 4.51V. I figured that the drive motor needs 12V and 8.80V probably isn't cutting it. To confirm, I ran a floppy power cable from a PC and left everything else connected to the 1040STf. It worked! I again checked the power connector going into the drive mechanism: this time it was 12.1V and 5.05V. Here's my question: Can anyone guess why I'm only getting 8.80V when I use the Atari power supply? There is some circuitry on the logic board that the power goes through, some transformers and capacitors, before it gets to the drive - could that be the cause? Here's a picture of the logic board, and a the relevant page from the SF354 service manual (which, from what I understand, is pretty similar). https://dl.dropboxusercontent.com/u/18477511/Atari%20SF314%20Logic%20Board.jpg https://dl.dropboxusercontent.com/u/18477511/Atari%20SF354%20Power%20Supply%20Diagram.jpg Any help on this would be appreciated! Thanks! - Rick Thornquist Quote Link to comment Share on other sites More sharing options...
exxosuk Posted April 3, 2015 Share Posted April 3, 2015 If the PSU isn't working unload then there is a problem with it. Going by how the caps are all 30+ years old there is no great suprise. Sounds like you have really bad regulation on the PSU under load. I have not looked at the floppy drive PSU as I don't think I even have one here. Though I have documented a lot of internal PSU's on my site. http://www.exxoshost.co.uk/atari/last/psu/index.htm Quote Link to comment Share on other sites More sharing options...
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