3D Controller problems with PAL Model 1 Saturn

[Eidolon]

Hi,

after de-mothballing my PAL Saturn after about 15 years, I notice that some controllers do not really work well with it anymore.

Hardware info:
- Model MK-80200-50
- Mainboard: Seems to be a VA1? (PCB info: Made in Japan, 171-7069B Main, 837-11892-01:PAL)

The symptoms are (tested with controller port 1 and port 2 - same behaviour to be observed)
- one 3D controller (set to digital mode) does not work when it is already plugged in during power-up. When I re-plug it in after power-up, it starts to work (and then works fine)
- a second 3D controller (set to digital mode) does not work at all, neither when plugged in during power-up, nor when re-plugged in after power-up
- regular, non-3D controllers seem to work fine, both when plugged in during power-up

What I already did is
- clean the Saturn controller ports with Isopropyl alcohol and bend the controller port pins up a bit again so they have a firmer grip towards the controller plugs
- clean the 3D controller plugs with toothbrush and Isopropyl alcohol
- clean the 3D controller "plug-in plugs" with toothbrush and Isopropyl alcohol
- clean the flat cable between mainboard and controller port PCB with Isopropyl alcohol

My questions:
- Do I have a problem with one or both of my 3D controllers, my Saturn, or both?
- What can I test to evaluate further and pin-point the problem?
My lab-at-home is equipped with soldering station, multimeter, logic tester, so I can use all of these to hunt down the error in either device (3D controller or Saturn)

Thanks in advance - any help appreciated!

[Eidolon]

In case anyone wonders - the culprit was F1 on the controller PCB. Replacing this with a 0,5A Picofuse did the trick.