I was printing on my IIISi tonight and, between
jobs, it switched from
working normally to displaying "50 SERVICE" (with the "50" flashing)
and not accepting print jobs.
This is one of the most common problem in the II and III series. Usually
a broken fusor lamp or problem in the AC Module. In the II/III it is ALWAYS
the small thyristor in the AC module. You can use a TIC106 in its place.
Well ,there are at least 2 versions of that AC block, one of which uses a
triac, not an SCR/thyristor...
And that's not always the problem. A 'stock fault' here has been a fuser
problem after warm-up, with the protection relay dropping out (the relay
on the lower PCB in the AC block). This is controlled by the circuitry on
the upper PCB, and the stock fault I've had (which took a long time to
trace the first time) is one of the electrolytics there physically
leaking, the electrolyte then causes a conductive path across the PCB,
and really conmfuses the protection circuit (there's a couple of
high-impedance nodes in that circuit).