asked Dec 14, 2001 at 3:43pm
Hp HP LaserJet 4

HP III 50 Service

Hello, I have the 50 Service message appearing during warm up. I feel it may be the AC power module or DC controller as the fuser element comes on for approx 5 seconds when first printer first powered up then goes off. I have determined this by placing a clip on ammeter on the power cord phase. The biggest problem I have currently is getting access to the guts of the printer. The printer is drawing 4 amps while the element is on. The sensor is about 1M ohm when cold, and the fuser element is 10 ohms. Any help here would be appreciated. How do I get the thing open?
Both those readings are kind of high. I'd suspect your meter isn't any good. There is a picture on the troubleshooting page under SX fuser which gives the readings you're supposed to get. While you're at it you might want to tweak the fuser connector on the dc controller. Other than that, you're going to need a part to fix it.
by moe on Dec 14, 2001 at 4:12pm Add comment
Hello again, my printer is 230 volt model which may explain the different element measurements. I managed to gain access to the AC power module and was able to see the light coming from the fuser. Checked all connectors etc. There appears to be a relay in the power module that clicks the moment the fuser goes off. Is this an indication of a faulty Power module? or is there another reason the relay clicks? Is it some kind of interlock. I am keen to know befor I go and order a new power module. Thanks.
by unknown on Dec 14, 2001 at 7:16pm Add comment
Check the thermistor and its controller board on the fuser, if the thermistor does not show any change in temperature during the first few seconds, the printer will assume there is a problem and cut power to the fuser down.
by Ally on Dec 15, 2001 at 8:01am Add comment
It's a bad ac power module. We don't stock the 230V versions.
by moe on Dec 15, 2001 at 10:59am Add comment
OK, Thanks anyway. I will check with local HP repairer.
by unknown on Dec 15, 2001 at 2:56pm Add comment
Its always the fuser or the AC power supply.

I have a 50 service error with my LaserJet IID that I use as duplex printer in the same room as the HP LaserJet 4 since the HP 4 is not a duplex model, its good to have a second laserjet in case of the main one breaking down.

Its never the case of the DC Power Pack, its the AC Power Pack or the fuser element blown.

The DC controller does not power the fuser element but it does power the sensors inside the fuser.
by Stuart on Apr 6, 2002 at 4:58am Add comment
I just discovered the same error on my series II (50 service) Can I assume its the Power supply, or the Fuser? Can this be fixed by me? (pretty mechanically inclined) , or is it best fixed by a HP authorized location? Is there a location where I can get the part(s) online? Info appriciated.....
by Mike on Apr 6, 2002 at 2:35pm Add comment
In my case with service error 50 problem was on the fuser controller board there is a transistor that is connected with a sensor on the fuser unit
(yellow an with wires) this transistor was malfunktion in my case i replaced it and the printer is warming up agian

hope this helps you solve your problem
by remi on May 20, 2002 at 5:24am Add comment