How does the STE detect floppy drive?

[ube]

I have this motherboard where the floppy interface is not working. I’ve replaced the WD1772 with no luck. Removing it all together gives me two bombs. The main symptom is no icons on desktop. However, I plugged a Gotek in upside down and lo and behold, icons! Which leads me to belivie that I grounded something that detected the floppy.

Looking at the schematics I’d guess I’ve grounded D0SEL and then done something with BO0SEL (U307).

Any insights? Or tips what to replace?

[czietz]

This is from memory, thus, anyone, please correct me if I'm wrong!

Afaik, TOS instructs the FDC to seek to track 0 and tests whether the track 0 bit in the FDC is being set. There's a separate signal on the floppy connector for the track 0 sensor. As for your problem: You should check the Yamaha PSG chip and the 74xx buffers that are involved in selecting the floppy drive. If the drive is not selected, it never reports track 0 reached.

[rubber_jonnie]

I'm in a similar scenario, the board no longer recognises the floppy. I've swapped out the 74XX buffers for known good, the sound chip for known good, the WD1772 for good, replaced the cable and still nothing. Oh yeah, and I also swapped the GLUE out for known good.

As it happens, all chips I removed work fine in my H4.

At the moment it is looking like a donor for my next H4.

It may well be worth buzzing out the pins to see if they are all connected as expected in the schematic. Also, my 520ST was not detecting any FDDs, and the GLUE was faulty, so worthwhile at least cleaning the connections to that, and if you have a spare, try swapping it out.

[Tomswork]

I do remember the the ym2149 or sound chip controls the drive select thru 3 bits not sure on the path with the 1772 or buffers

Tom

[ube]

@rubber_jonnie, if you were to turn the connector upside down, do you get the icons?

[exxos]

@rubber_jonnie, if you were to turn the connector upside down, do you get the icons?

IIRC it just goes right to desktop without icons.

[JezC]

At the risk of stating the obvious/asking a stupid question, you have to connect the 34 way cable into a Gotek the other way up than a normal Atari FDD (or at least I have had to in my Ataris and my external Cumana drive) ...so when you say that you connected the Gotek upside down, does that now mean you connected it the same as an Atari floppy?
:hide: :shrug:

[ube]

@rubber_jonnie, if you were to turn the connector upside down, do you get the icons?

IIRC it just goes right to desktop without icons.

This is the thing. I do get icons that way.

[ube]

At the risk of stating the obvious/asking a stupid question, you have to connect the 34 way cable into a Gotek the other way up than a normal Atari FDD (or at least I have had to in my Ataris and my external Cumana drive) ...so when you say that you connected the Gotek upside down, does that now mean you connected it the same as an Atari floppy?
:hide: :shrug:

Yep. Upside down is the right orientation for a Gotek. When I forgot it I got the icons but no access.

[rubber_jonnie]

@rubber_jonnie, if you were to turn the connector upside down, do you get the icons?

I'd have to go and check, I really can't remember.