Most of the time when we have communication problems (lost or weak conecction), it is most likely due to a very poor quality of the copper tracks and the solder pads in the SIO connectors (any or booth). The solder pads suffer from cold solder (solder crack) or the pads themselves offens to break and isolate from the circuit, interrupting communication with the computer.
Both connectors are twins, they have the same connections pin to pin (paralell).
To fix this, I solder some pieces of wire from pin 7 to pin 7 and resistor R2, pin 5 to pin 5 and resistor R1, finally both pin 3 are connected to Jumper J2. Remember the pins order, on the PCB pin 1 is marked, and in the same row 1-3-5-7-9-11-13, and in the another row (bottom row) 2-4-6-8-10-12 . Both resistors are marked on pcb they are very close to right sio (looking from bottom of the pcb)
Do not feel satisfied with just reflow the solder, those little piece of wires are the final and definitive solution.

Hopefully this will fix the problem and your floppy drive will work for many years.
sorry for my English, I speak Spanish. :D

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