Byte Hamr Labs

The Liron card runs on a UniDisk's IWM now

/ UniDisk 3.5 controller / updated 2026-10-11 unidisk liron iwm repair m6

The Liron card works again. Its IWM died when a loose strand put -12 V on /WRREQ, and I swapped in one from a dead UniDisk controller board. The IIe sees the working UniDisk on slot 5 again.

After the swap: the working UniDisk shows up again on slot 5, drive 1, /REF800K at 1600 blocks.
After the swap: the working UniDisk shows up again on slot 5, drive 1, /REF800K at 1600 blocks.

Two IWMs desoldered, one socket added

The UniDisk’s own controller board, the IF-83, uses the same IWM as the card. Both of my test drives came with a dead IF-83, so one of them gave up its chip. It was soldered in at IC103.

The donor: a dead IF-83 drive board with the shield off and its IWM desoldered from IC103. No socket here either.
The donor: a dead IF-83 drive board with the shield off and its IWM desoldered from IC103. No socket here either.

The card is Apple’s 3.5 Floppy Disk Drive Interface Card, 820-0117-A, on a board marked IF-98. Its IWM sits at IC105, and it was soldered in too. So that was two 28-pin chips to desolder, and nobody makes them anymore. I was sweating, and it tested my desoldering skills and my patience. I put a 28-pin socket in at IC105 so the next swap is pull and push.

The Liron card (820-0117-A) with the dead IWM desoldered and a new socket at IC105.
The Liron card (820-0117-A) with the dead IWM desoldered and a new socket at IC105.

Same part on both boards

MarkingFrom
DeadVF4060-0001, 344-0041-B, 543 V 9012, MEXICO-Rthe Liron card
DonorVF4060-0001, 344-0041-B, 520 V 7539, KOREA-Aa dead IF-83 drive board
The dead IWM from the Liron (top, marked with an x) and the donor from a dead IF-83 drive board (bottom). Both are 344-0041-B.
The dead IWM from the Liron (top, marked with an x) and the donor from a dead IF-83 drive board (bottom). Both are 344-0041-B.

If your Liron card has a dead IWM, the 344-0041-B off a UniDisk 3.5 controller board (IF-83) works in its place at IC105. Both are soldered in, so plan on desoldering two chips and adding a socket.

The Liron card with the donor IWM in the new socket at IC105.
The Liron card with the donor IWM in the new socket at IC105.

Writes work too

Reading a catalog only proves the card can talk. A write needs WR and /WRREQ, the two pins next to where the -12 V came in. So I used ADTPro to send my REF800K image from the Mac onto disk 2 through the repaired card, and read it back. The card writes fine.

That disk was the one my board formatted and wrote in M5, so that copy is gone now. Once the host side is rebuilt, my board gets to format it again.

The Mexico IWM is done, and the other dead IF-83 has the only spare I’ve got left. RIP. Now I have to bring this board to fruition so it didn’t die in vain.

Still open