VOGONS

TC430HX onboard Floppy connector read only

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First post, by octopus

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Hi,

I have a TC430HX socket 7 motherboard, which is my main retro machine.
It has an onboard connector for floppy drives, however that seems to malfunction.
The drive gets detected and I can read floppy's, boot from them etc. I can not write floppy's.
After analysing and testing, my conclusion is that the issue resides on the mainboard side.

What I've tested:
- change disk drive: same result
- change band cable: same result
- check BIOS settings: there is an option to make the drive read-only. I've set that and afterwards put it back to read & write, so the setting is written again. Results are the same
- add ISA controller card and connect the drive there: the drive works fine, both read and write options

My question is: can there be a way to fix the motherboard connector? Can you help me figure this out and what would you need to help me on that?
If there is no way to fix that, I'll stick to read only and keep my eyes open for an extra ISA floppy controller card (I have only one and that is in use in another machine).

Looking forward to your thoughts!

Reply 1 of 7, by Tiido

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Pin22 on floppy connector contains the data to write and pin 24 is the signal that enables writing, I would be investigating these pins, maybe you have a bad trace on pin 24.

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Reply 3 of 7, by Guld

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when you say you can't write floppies. Do you mean it acts like it writes (with no errors) but actually doesn't, or do you get an error of some form?

From what you've tested it does sound like something on the motherboard. I'd investigate the pins mentioned above.

Reply 4 of 7, by octopus

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Thanks for the quick replies!

Masaw wrote on 2025-11-02, 13:55:

by "write" you mean formatting a floppy / writing floppy image into a floppy or just typical copying files from hdd to a floppy?

Copying, trying to format or write anything to a diskette gives the message 'write protected'. Oh and yes, I've checked if the hole is closed.

Guld wrote on 2025-11-02, 13:59:

when you say you can't write floppies. Do you mean it acts like it writes (with no errors) but actually doesn't, or do you get an error of some form?

From what you've tested it does sound like something on the motherboard. I'd investigate the pins mentioned above.

Tiido wrote on 2025-11-02, 13:47:

Pin22 on floppy connector contains the data to write and pin 24 is the signal that enables writing, I would be investigating these pins, maybe you have a bad trace on pin 24.

This is the connector. There seems to be 1 pin missing, but if I'm counting correctly that is not pin 24.

The attachment tc430hx_floppy.jpg is no longer available

Reply 5 of 7, by Guld

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pin 5 is unused, so the missing pin is not a problem.

Pin 28 is the write protect pin that tells the computer that your disk is write protected. It is connected to the write protect sensor on your floppy drive. And since the drive works with a different FDC card, it sounds like your motherboard has an issue with that pin. It is erroneously telling you the disk is write protected when it is not.

This signal should be low (ground) when the disk is write protected, and high (+5 V) when it is not.

Check the motherboard for any damage to that line, maybe trace it to where it goes on the board and check for continuity (powered off of course).

Did you use the same FDC cable when you tested it and it worked with the second FDC controller? If it was different cables or locations on the cable, it could also be a cable issue with pin 28.

Reply 6 of 7, by maxtherabbit

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Sounds like a broken/missing pull up resistor situation

Reply 7 of 7, by nuno14272

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are not the disks write protect ? is the hole on the diskette open or closed ? just checking.

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