LaserJet III - Service 50 Error - Can't Solve

Archived from groups: comp.sys.hp.hardware (More info?)

replace the heater safety board in the ac power supply with a NEW one.
(or repair the little board)
also check for stalled upper fan.

regards,
Koen.


"dh" <djharrid@bellsouth.net> schreef in bericht
newsgEbc.5497$tT3.4773@bignews6.bellsouth.net...
> I'm doing long distance trouble shooting for a friend who has the infamous
> "50 Service" error.
>
> Thus far he has (in order):
> 1) Replaced fuser with new (Thermal switch was bad).
> 2) Replaced AC supply with referbished
> 3) Checked DC voltages (+24, +5, -5). All good.
> 4) Replaced DC Controller with referbished.
> 5) Continuity checked cables between the DC controller and fuser and AC
> supply. Good.
>
> I installed his old DC controller into my LJIII and it works.
> Fuser does come on briefly during power-up.
>
> All this and still no-go. Any ideas? Maybe the AC supply is still bad?
>
> David
>
>
>

Archived from groups: comp.sys.hp.hardware (More info?)

My friend checked the resistance of the thermistor
on the "new" fuser. Reads shorted. Go figure.

I think too many measurements were made over the past
two weeks and this one was missed. His old fuser has a
bad thermal switch, but the thermistor reads good. Perhaps
it can be swapped.