Laserjet 4 error code "50 Service" help

I need some help in identifying the problem associated with an error code "50 Service."

The printer automatically begins a 05 SELF TEST after power on and then displays a "50 Service" code. Seeing that most 50 error codes are fuser related and I had never replaced the fuser or even serviced the printer before this, I assumed that the fuser was the issue. I ordered a maintenance kit and replaced it. It went through the 05 SELF TEST and 02 WARMING UP mode and then I heard a click. Now I still get the "50 Service" error code again. Turning the printer off for 15 minutes does not fix the problem.

This is not identified in my book or on your website. It must be more serious than just a fuser related issue.

Any Suggestions as to what a "50 Service" code means?

Thanks, GG**2

You probably have a bad power supply. The power supply makes
logic voltages and supplies 110 volts for the fuser. The "50 Service" can mean that the fuser is not warming up or that it has overheated. Is there any way you can get these fusers into another LJ 4 to test them?

If you have a meter you could check for 110VAC fuser voltage at the power supply. The connector is in the front end of the supply. Remove the plastic side cover and whatever sheet metal to get at the front end of the supply and check for 110VAC at J102. There must be a relay in the supply that turns the fuser on at a certain point in the power up cycle.

The diagram shows the fuser power going through the High Voltage supply but I think it is just a convient place to hang the fuser connector

Best bet might be to find a parts machine. I have seen working LJ4's at the surplus places for $20.

Al

The power supply is a possibility, but very unlikely on this model ... more likely, the original fuser may be being mixed up with the replacement fuser ... or you received a defective fuser as a replacement ... I would first try to get a warranty fuser from wherever you purchased the kit ... power supply issues are not that common ...

Thanks for your inputs, Big Al and CS Steve.

I went through and checked both fusers. Actually both seem to test the same with a ohm meter. About 1-2 ohms on the big pin connector and about 280K ohms between the little pins on top. I then pulled the power supply and tested it on the output of the big connector. When I turn on the unit, there is 110V present when first turned on. After about 5-10 seconds, I heard a click like a relay and the 110V was then no longer present on the connector. This was tested without a toner cartridge and the fuser in their places. Don't have a clue what to do next except look for a parts machine.

Any other suggestions?

Thanks, GG**2

Is this printer plugged into a power strip or a dedicated circuit?

Yes, the printer is plugged into a surge protecting power strip and has been for several years. I'll try plugging it directly into the wall.
thanks.

When you have a 50 error on the 4/4+/5 machines, you have power off for 15 min after installing the new fuser until it clears the error. If the error doesnt go away, replace the power supply RG5-0531. You probably can buy it from Printer techs or PM me and I'll sell you one. Better yet upgrade to a newer printer, cause HP 4's are old. Your decision. :)

Is there a good replacement printer for the hp lj 4+? I need it to be inexpensive but reliable
any help would be great.
thank you
heather

The LaserJet 4 Series is still a reliable printer, just needs more care as they are a older machine, but if you service them well and fix all the known faults then the machine will work for a decade or so, or until toner can no longer be sold, the LaserJet II printer can be extermly reliable printer if they are service correctly.

Replace the fuser and power supply, and your be okay, thats how I deal with 50 Service Errors it can be the DC controller, but thats rare.

You can repair the fuser unit, but its cheaper and easier to buy a refurbished one, you can replace the fusers element to get the fuser working, but then you need to refurbish the entire fuser, its a lot of work, its quite a diffcult job.

Basic Parts that Make up a LaserJet 4 Fuser:

• Upper and Lower Fuser Rollers.
• Various Gearsm diffrent sizes too.
• The fuser chassis, and supports.
• Thermal Sensors and wiring.
• Bushings for upper rollers.
• Fuser Heater.

There is lots more, you need the service manual to know how to disassemble it.

If you do decide to go with repairing your existing fuser you must clean it first, and replace the parts above, they are sold as a kit at various places.

Thats the fuser taken care of, the power supply can have a capacitor that failing or gone hard since it has liquid inside there, you can go to any electronics store such as Radio Shack, and replace the capacitor as long its the same attributes such as voltage, such, then you need need skills for soldering and solder removal.

This is one way to fix your problem.