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Guide to disassembly and reassembly of HP LaserJet II and III

(From: Alexandre Souza (taito@terra.com.br).)

I used to fix lots and lots of HP II and HP III here in Brazil. So, with time, I developed a "checklist" for HP II and III repairing, that is safe enough to keep the printer working for years (4 years and NO defects whatsoever) and customers were happy. I'll include things not necessary for Americans (Brazil is HOT. Hotter than USA!) because friends all over the world may need this info.

What you need: Isopropyl alcohol, toner sucker, good screwdrivers, cotton, cotton swabs, screw picker (that little handy tool to pick/put screws in tight places), some rags - and lots of space!

I'll take the HP III as an example, The HP II is equal, with very minor differences. Please apologize me for any incorrections, since I'm telling everything from memory.

  1. Be prepared to do a complete tear-down of the printer. Dismantle it to the last screw. This is a day-long work, so better you are prepared to do it. If you let for the following day, you WILL forget where the assemblies go, and will make your job a trip to hell.

  2. Take the body cover entirely off. You will take total 6 screws, one of them in the back of the printer. You take it off pivoting it on your direction. It is a clumsy process, don't know why HP didn't made it easier.

  3. Take the front "shield" off. The "front shield" is a big sheet of metal that covers the entire front of the printer. 5 or 6 screws, 2 ol the sides, 2 on the front, 1 or 2 on the top.

  4. Take the Power Supply off. You need to unscrew 2 screws on the front of the printer, and one on the back of the power module, besides the main motor. Also, disconnect the cable of the motor from the power module.

  5. Look at the solenoids of the power module. It is very common to have the solenoids' felts inside it became a messy glue. Take the metal flap off (take care with the coil) and clean everything that seems messy. Take 2 or 3 small squares of electrical tape, and put in the nucleus of the solenoid. Do it on both, replace flap. Don't forget the coil! Check the solder of the power module.

  6. Now is time to take the ozone filter support out. This is a black plastic piece with 2 screws - one on the top, and another near the motor. Clean everything with compressed air and a rag. Be sure the filter is unobstructed. Better if you CHANGE the filter, but these are impossible to be found in Brazil. So you clean it. Or you will have some messy ex-gears. You have been warned.

  7. Take the fuser out - it has 4 screws on the corners. Take care of it, there is a big and expensive lamp inside, and you don't want to buy a new one, eh? We will not disassembly the fuser module if not needed. But if you open the cover, pick the cleaning pad out and see black lines on the fuser roller, it is time for a cleaning!!! Dismantling the fuser is a complicated matter, but here we go: First of all, study how every piece fits its place. You should begin the dismantling by the right side, taking great care with the lamp. Take off the plastic pieces at the sides of the fuser, take the lamp out, so you are free to work. Store the lamp in a quiet place (no one should even touch it he he he) and don'ts touch the glass with your fingers - do it by the ceramic sides, or the wires. Clean the lamp with cotton embedded in isopropyl alcohol and set aside. Take off the locks of the gear on the right side of the fuser roller, there is an equal lock on the left. Take off the fuser roller, and PLEASE don'ts scratch it. You will see 2 thermistors on the fuser assembly, covered with yellow plastic. Clean it with cotton swabs and alcohol. If they are damaged (plastic is broken, missing a piece, has a hole, etc) CHANGE IT. If the surface of these thermistors isn't smooth, it WILL mark the surface of the fuser roller and WILL DAMAGE it. And this is not a cheap part. Everything clean, assembly it again, doing backwards what you did to unassembly. Remember this is a GOOD time to change the fuser roller.

  8. Take off the AC module, where almost all the CX engine problems are located :o) This is the aluminum "tower" besides the fuser assembly, and where the AC cable comes in. Dismantle everything, change the little little little heat accumulator (yep, it is so little that should be called "heat accumulator") from the black TRIAC besides the mains power connector, and put a good heatsink with heat paste there. Also, clean THOROUGHLY the upper fan assembly, because when it fails, it can make things hotter. Hot enough to melt the fuser gears. :o) Remember: ERROR 50 = TRIAC open. A TIC 226 fits the bill on place. Of course there are other causes for error 50. But I've never seen that in Brazil.

  9. Time to go to paper path! Take the 4 screws that locks the registration assembly in place. The registration assembly is the module where you have the big green handle. Clean everything and note if the "L" of the front is straight. If it doesn't make a 90 degrees angle, fix it. Also, change the separation pad. It is the culprit of 99% of the pickup paper problems. What? You live in Brazil and cannot buy new separation pads? So clean the black mess that was a long time before a hard rubber, and put some kind of rubber or cork on it. Also, take about 10 cm of isolating tape and cover the lower half of the "separation pad" you did. The printer will not give ONE pickup error for YEARS. BTW, I never had one return of this method. When you put the registration assembly back, don'ts forget the small yellowish piece on the front roller is assembled pointing the frontal part of the printer!!! This is very important!

  10. Take the pickup roller out and clean it thoroughly. Use turpentine to make it softer, it will last years! Of course, if you have a replacement unit, better to use that.

  11. Using a cotton swab, alcohol and LOTS OF PATIENCE, clean the corona wire. Be careful as you can, not to break the diagonal wires that surround it.

  12. Do a GOOD cleanup on the inside of the printer. Use compressed air (with a dehumidifier) and don'ts throw air in the scanner assembly. Better never mess with that. Only open the scanner assembly if you HAVE a problem with it. Hope you never have.

  13. Of course you already took the toner cart off, eh? Well, you have a black metal plate, with instructions of putting a cart there. Slide that plate to right, and move it up. You will see a very nice and delicate frontal mirror. Use only cotton and alcohol to clean that, and after only cotton to polish it. Make it clean, and close the lid. Of course, you don'ts want to let it exposed. A nick on this mirror, and there goes your print quality away.

  14. You have 2 contacts on the left part of the printer cover. They touch the fuser assembly below. Do a continuity test there, you should find some ohms, but continuity. If you don'ts find it, you have a broken "erasing lamp" inside the printer cover. 2 screws keep you far from them, better change it now

  15. Close the printer cover, turn the printer upside down, take out the plastic pan on the bottom of it, take the metal pan, clean everything including the lower fan. Of course, a lower fan broken, is a laser printer broken. NEVER, I said NEVER run the printer with the lower and upper fan disconnected, OK? Do you remember what I said? You have been warned 2.0 :o)

Well, this completes my "HP Refurbishing method". To reassemble it, you do the following:

And so you have a healthy HP III. It will last for YEARS if you did it right. don'ts forget to put a fresh new cart of toner and it will last forever. Of course, you want to clean everything externally too.

The common disclaimers apply here. Do it at your own risk. I've fixed some 500 HP LaserJet IIs and IIIs, and never had a problem, return or anything doing that. Your mileage may vary. Greetings for Brazilian friends, and for all around the world that uses that guide. :o)

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