exxos's Atari, Amiga & retro forum

Hi everybody. I'm experiencing some trouble with my Atari 1040 STE / 1MB / PSU SR98 / CA4003290 motherboard

At startup, the floppy drive makes noises then the desktop is displayed without drives A nor B (video 1: https://youtu.be/DYs9ybEFtOI).
If I add an ultrasatan, the floppy drive still makes noise, the ultrasatan works fine (all programs too), but no access to the floppy drive (Message is : "the selected drive does not exist") (Video 2 : https://youtu.be/-Gx67mWr7qY)

Using the diagnostic cartridge
- Memory 1 MB -> OK
- ROM -> OK
- Keyboard -> OK
- Audio -> OK
- floppy drive test -> noise then message "F0--Drive not selected" KO

Here are all the tests and actions I did (but did not change anything)

What has been tested (on another machine) so I'm sure they work:
- WD1772 -> OK
- DMA C398739-001A -> OK
- PSG YM4921F -> OK
- Floppy drive -> OK
- Floppy disk -> OK
- CPU -> OK
- C301712-001 -> OK
- U305 (SN74LS06) -> OK

What has been done but still do not change anything:
- 4700uF Exxos capacitor -> no change
- Mandatory #1 - PSU SR98 Recapped -> no change
- Mandatory #2 - Not necessary, 4 strips of 256KB 8 chips without parity -> no change
- Mandatory #3 - DMA Pull Up -> no change
- Mandatory #4 - 1772 Pull Up -> no change
- Mandatory #5 - CPU changed to HC Type -> no change

What I also did but (again) did not change anything:
- Changed the cable to the floppy drive -> no change (Power to the FD is good +5v +12v)
- Changed U304 (74LS74) -> no change
- Changed U306 (74LS74) -> no change
- Changed U307 (74LS244) -> no change
- Changed U308 (74LS245) -> no change
- Changed C204, C205 -> no change

So I don't know what to do anymore. I also tried looking for a cut trace on the motherboard but couldn't find any.
Would you have an idea (or two) to explore ?

Thanks.

Verify the continuity on W300 and W301 bridges. Look for cuts.

... had the same problem with an Atari Mega ST and on the sound chip was missing two data signals. So see the schematics and check this ...

You have the right STE DMA Chip so the DMA and FDC Pullup are not needed.

I'd agree with @frank.lukas , it's definitely worth a look at the sound chip. Pins 19, 20 & 21 are involved in FDD selection.

... D10 and D11 were missing on the PSG coming from the DMA. There are errors with the test cart on joystick and PSG ...

frank.lukas wrote: 03 Feb 2023 21:19 You have the right STE DMA Chip so the DMA and FDC Pullup are not needed.

Please inform me of the research material which lead to that conclusion.

I had no Icons on the Desktop

1. Replace PSG with not change the fault
2. Connect the test cart with the testboard and couldn't do anything with the error message
3. Read the service Manual, see picture ...
4. check all 40 connections on the PSG and found D10 and D11 had no connection to the PSG
5. Fix D10 and D11 reboot the machine and all was fine with the floppy and the icons on the Desktop ...

tzok wrote: 03 Feb 2023 19:24 Verify the continuity on W300 and W301 bridges. Look for cuts.

What is the good wiring for W300 and W301 bridges ?

doc wrote: 04 Feb 2023 17:08 At startup, the floppy drive makes noises
...
What is the good wiring for W300 and W301 bridges ?

Exactly what happens with the drive when TOS attempts to read a floppy ? Does the motor turn on? Does it move the head? Does the drive led turn on?

If these are true, then your problem doesn't seem to be related to those bridges or the PSG signals.

frank.lukas wrote: 04 Feb 2023 15:55 I had no Icons on the Desktop
5. Fix D10 and D11 reboot the machine and all was fine with the floppy and the icons on the Desktop ...

But your floppy drive showed any activity at all at startup and with the floppy test? Probably not. So I'm not sure it's the same scenario than the OP one.

Hooray it's fixed!

The problem came from a trace probably cut (impossible to see with the naked eye) between the WD1772 and the 7406 (U305) on inverter D. Everything is back to normal.
Thank you all for your help which re-energized me and gave me some clues on how to detect this error.