HP DesignJet 750c PLUS : How to replace belt????

MGD King's Thoughts

Getting What's Inside My Head Out

HP DesignJet 750c PLUS : How to replace belt????

My good friend Billy posted an article sometime last year that he thought would be beneficial to anyone who has ever had to work on a HP DesignJet 750c PLUS, more specifically changing the belt. Sounds simple enough but go read on, this was a real engineering marvel feat! So thanks for sharing this info Billy! I’m posting it here!

How to begin.... If your drive belt has "shredded itself" and you see bits of black rubber dusting the inside of the printer or if you notice that certain teeth on the belt are missing, a full disassembly is the only way to go. I tried the dental mirror approach but realized that it was pointless since my belt had become entangled around the drive motor. This is a very important piece of information.

1. If the carriage will not move freely from side to side and it is not locked the fibers of the belt are probably wrapped around the gear of the motor. The only way to tell is to take it apart.

2. My 750c Plus - the teeth face each other and not outward. I cannot speak for other models.

3. Take the printer outside on a clear afternoon, have some towels, a drop cloth for the ink well, Leave it secured to the stand, if you have one, and start taking out the screws on the 2 side caps first. There are 3 screws on the inside of the clear lid. They are different sizes and thread type so I just laid them in the roll cover which was in the down position. The ribbon cables and door sensors are on the side with the controls. Take precaution when sliding that cap out as you have to remove the sensors and ribbon cable before you can let go. (2 people recommended for this stage).

4. When you start to take the end cap off the clear lid will want to fall. Have someone ready to catch it. Remove the left cap after you pull the power button out / off (like on an old car cassette desk) toward you and set aside.

Now you are looking at what most people consider an insurmountable task. The engineers that designed this thing should have already sent a man to Mars and back. I started with the simple things first.

5. I had a lot of rubber pieces inside so I used canned air to blow out all of the debris toward the front and whenever possible to the left and right of the middle. I used a crevice tool on the Shop-Vac (not around the boards) to clean any excess off of the motor mounts and body.

6. After cleaning the thing, get a beer, take a break, grab an extra set of hands. You will need that little bit of sanity over the next half hour.

7. The old belt can be removed by cutting it if you wish. I chose to loosen the 2 Torx bit screws next to the motor housing. There are 2 wires going to the motor so pay attention to where they go. Have your extra hands hold the motor while removing those screws. Tilt the motor and slide the belt off. Clean the belt gear if dirty. I used an old toothbrush and an exacto knife.

8. Right above the motor mount is the metal guide strip. Use the utmost care in removing the screw and strip. It is pre tensioned so you should have no problem putting it back.

9. On the left side of the carriage rails is a tension pulley. You should slide the carriage to the left hand side but not all the way. pull out on the pin and spring and the triangle tensioner should slide out. Remove the belt from this, slide the belt out of the underside of the carriage, and carefully pull the remainder from the printer.

10. Go have a beer.

11. Clean up any other residue of belt mess and

12. Feed the belt back through the tensioner and lock in place.

13. To this day I will never be able to tell you how I got the belt back into the carriage lock. Good luck and 2 sets of long needle nose & tiny flathead screw drivers.

14. Once in the carriage lock. Lock in the tensioner and stretch the belt over to the motor mount. Put the motor in from the bottom at an angle and slide the belt over the gear. Rotate over and screw that bad boy in. Replace the wires and guide strip.

The rest is just putting the case back together. Good luck and send me a message if you want pictures.

If you have further questions you can reach out to Billy at his website.

Loading