akimmet wrote on 2024-10-04, 01:58:

You can use a high density PS/2 floppy drive on a model 30. The drive will still operate as a double density drive. The system's controller just won't be able to read high density floppies, even though the drive is capable.

8086 Model 30’s can be made to read and write 1.44mb disks, you just need the correct drive and a little fidgeting

Video in here explains how
https://forum.vcfed.org/index.php?threads/ibm … sk-drive.63619/

rmay635703 wrote on 2024-10-04, 22:38:

8086 Model 30’s can be made to read and write 1.44mb disks, you just need the correct drive and a little fidgeting […]
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akimmet wrote on 2024-10-04, 01:58:

You can use a high density PS/2 floppy drive on a model 30. The drive will still operate as a double density drive. The system's controller just won't be able to read high density floppies, even though the drive is capable.

8086 Model 30’s can be made to read and write 1.44mb disks, you just need the correct drive and a little fidgeting

Video in here explains how
https://forum.vcfed.org/index.php?threads/ibm … sk-drive.63619/

Oh nice! Thanks, I'll take a look!

And WRT the power supply, I looked at it again. I incorrectly said the -12 and +5 were shorted to ground.

Really, the +12 and +5 are very low resistance to ground. Not fully shorted, but resistance is in the 10-20 ohm range.

I don't know enough about power supplies to know if that is troubling, or just due to how they work. Is that normal?

I still need to open it up and look for anything suspicious as well.

Alright, back trying to see if this system will work again.

None of the tantalums are currently shorted.
I've got the system completely disassembled.

I'm seeing a short on the motherboard between the P8 power connector (should be +5 V) and ground (P8 pins 5,6, etc.)
However ,the +5 lines on the P9 connector (P9 pins 4,5,6) are NOT shorted to ground.
This occurs with the riser card removed and memory removed (CPU, and ROM chips are still in place).

And suggestions for what this particular +5 volt line is connected to? Or can anyone point me to a wiring diagram that I can use to try to track down the source of the problem?
My board is the P-Planar board.

Guld wrote on 2024-11-17, 21:20:

And suggestions for what this particular +5 volt line is connected to? Or can anyone point me to a wiring diagram that I can use to try to track down the source of the problem?

Look here: https://archive.org/details/ibm-ps-2-model-30 … matics/mode/2up - The P7 connector is on page 1, and as you see, the PS/2 model 30 (8086) is just not XT/AT compatible. That pin is supposed to be grounded.

mkarcher wrote on 2024-11-17, 21:38:

Guld wrote on 2024-11-17, 21:20:

And suggestions for what this particular +5 volt line is connected to? Or can anyone point me to a wiring diagram that I can use to try to track down the source of the problem?

Look here: https://archive.org/details/ibm-ps-2-model-30 … matics/mode/2up - The P7 connector is on page 1, and as you see, the PS/2 model 30 (8086) is just not XT/AT compatible. That pin is supposed to be grounded.

Ah thank you! I wondered if it was the same pinout or not but thought it was. That explains it! Thanks for the link!