LaserJet III - Service 50 Error - Can't Solve

[dh]

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

 

[RWatson767]

David

LaserJet III - Service 50 Error - Can't Solve

All this and still no-go. Any ideas? Maybe the AC supply is still bad?

The pins on the left end of the fuser can be inserted off by one pin. Otherwise
it is good to have a second working printer to test components by elimination.
And of course reseating/insuring the connection of any connectors is a must.
Bob AZ

 

[Jay Bollyn]

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

David,

I suggest post here:

http://forums1.itrc.hp.com/service/forums/categoryhome.do?categoryId=413

Just say: Please Dewaine, Jay said you might be able to help me...

-- Jay

 

[jbuch]

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.

You can get caught in a loop where:
1) you put in a new AC power unit
2) a bad fuser zaps an AC power supply

and you can kind of repeat it especially if you swap fusers around.

So I finally learned not to put in a new AC power unit until somehow I
had proven that the fuser was OK.

Most of the time, I actually remember to do this.

Jim
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[Bill Crocker]

Sounds like a defective, burned out fuser unit. Check eBay for deals.

Bill Crocker

 

[dh]

A new unit (not referbished) was installed, but of course it could be bad.
The thermistor resistance is correct and the thermal switch is closed as it
should be.

 

[CCSI Inc]

Be sure you have the pins on the AC Power supply lined up.
"Fuser does come on briefly during power-up", more often than not, this is caused
by a bad AC Power Supply.

 

[dh]

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.

 

[magpie]

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

Have you checked the upper cooling fan? The one sitting on top of the
AC Power Supply? A lot of times that is the culprit. If it's frozen
up or burned out, you will get the 50 service error message.

Frank

 

[dh]

The original fan was frozen up, but was replaced with a new one.

 

[dh]

My LJIII printer was sick during this troubleshooting of my friend's printer
so between the two of us we've learned a lot and can take a LJIII apart
while blindfolded. I bought a service manual in pdf format on-line. Wish I
had the manual before all this started. For my printer I replaced the AC
supply and fuser before finding it was the DC controller. Spent more than
the printer is worth, but once I started I just HAD to fix it.