exxos's Atari, Amiga & retro forum

Hi,
I purchased an external floppy for Atari ST a few months ago, it’s a no name containing a simple power circuit and a TEAC FD-235.
I tried it yesterdays it’s not working, Floppy LED turns on briefly at startup but after that the drive is not recognized.

I troubleshooted a bit this morning, the 7805 chip was dead giving 4.4V when powered with 5V and 5.5V when powered with 6V. I replaces it with a new one and now I get a steady 5V but still not working.

I wanted to replace the TEAC drive with one of my spare to try but no luck ☹️ I tried with two different EPSON 380 and an Amiga 600 drive but still nothing.

I tested the cable and I have continuity on all wires and it seems to be properly wired.

I was wondering, as all my spare drives are originally internal ones, do I need to change DS0 to DS1?

6V input sounds a bit low still. IIRC they need 2volts high minimum, but you would have to check the datasheet. 9V would probably be better.

I use 9-12v with my external FDD, it has what sounds to be a similar 7805 circuit to mine.

And yes, it needs to be DS0.

Thanks guys, you were spot on, I was too shy with my 6V.
After using proper 9V the FDD works fine.
A new 7805 and proper voltage and I now have my first external floppy.

olivier.jan wrote: 17 Oct 2021 19:53 Thanks guys, you were spot on, I was too shy with my 6V.
After using proper 9V the FDD works fine.
A new 7805 and proper voltage and I now have my first external floppy.

Good stuff :)