Need help -- HP 1220c Rehab

[vtjet]

(Correction -- the thread title says 1220c -- should be 1120c -- sorry!)

I picked up an old used HP1120c to do printing on balsa. I already own a Canon S600 and an Epson 1280, and yes, I do know about the superiority of other brands than HP. Nevertheless, I'm forging ahead, and would appreciate any help rehabing this printer.

CARTS:

I've removed the HP-45 and HP-23 carts and cleaned out the HP-45 with distilled water and refilled with pigment ink. It seems to work well.

I injected 8cc of distilled water into each color chamber of the HP23, and after a little work and a little time it seems to work also -- yellow needs a little more work to remove all lines, but I basically had written off both of these carts and sent for aftermarket replacements -- yet they both might actually work. I'm amazed that you can actually get dried out carts to work.

MECHANICS:

I removed the case and cleaned out the ink cleaning station -- one small pillar of dried ink -- nowhere near the head -- so I'm guessing the printer didn't see a lot of pages.

I cleaned the encoder strip with damp paper towel.

I removed the drive belt and repositioned it to move the wear point away from the motor driver gear -- it was okay, but I wanted to even out the wear.

I cleaned the rotating cleaning station wipers with water and paper towels.

I cleaned the printhead guide rod, and put a drop of tri-flo lubricant on it and spread it with a paper towel.

I did notice that there was a small but definitely noticeable amount of drag ( with the drive belt removed) when sliding the printhead left or right. I would think that this should be very smooth and easy.

So I checked out the way the printhead bears on the printer and there are two bearing points -- the guide rod, and a lip of sheet metal located i front of the printhead. It looks like the printhead is supported in front only by a plastic block that rides on the sheet metal. And the metal it slides on is not what I'd call a good bearing surface -- it has been worn clean and shiny by now, but must have originally been a rough finish like the rest of the sheet metal.

Is this correct? Is the print head supposed to slide on the sheet metal via a plastic block, with no roller?

I ask because the printer will sometimes print a full page -- other times it will stop after partially printing and blink the top two lights -- meaning "paper jam". After looking at the action closely, I have noticed that this occurs NOT when the paper rolller motor is trying to advance, but when only the head is traversing. For instance -- it may happen when I open the cover as it starts to move the head to the cart changing position. And I'm guessing that sliding friction is the culprit.

Any other guesses here?

I'm not sure how it senses there's a mechanism "jam" -- as a guess, could it be current sensing for the motor?

Any help would be appreciated. I think I'm close to getting this printer working again.

Thanks!

 

[vtjet]

Followup:

After disconnecting the toothed belt again and removing the encoder strip I did some more sliding of the printhead back and forth on the guide rod. I found that if I tilted the printhead slightly and slid fast it would catch. I decided that most of the friction was coming from the guide rod bearings, not the sheet metal/sliding block that I mentioned earlier.

I then decided to remove the guide rod and printhead so I could get to the bearings and see what was happening.

The guide rod is held by a clear plastic cam, with gear teeth on the outside -- presumably those teeth are used to adjust the rod's position via the cam by using some special tool at the factory. This would adjust the guide rod alignment in the printer.

I simply used an Exacto knife to scribe a line onto the printer's plastic end plate, using the edge of the cam to scribe against. This marked the exact position of the cam, so I could return it there again when I re-assembled it. I then removed two screws from the left cam, and one from the right one.

The left cam was then rotated until its tabs matched slots in the end plate and it could be removed. This freed up the guide rod, and I removed it and the printhead.

The printhead had two metal clips over the bearings. I pried those off. I found that underneath those were two felt wipers -- shaped like thick washers.

I took those off and finally saw the bearings -- basically bronze bushings in the form of two plates about 1/8 thick with a hole in them -- embedded in the plastic of the printhead. These were a definite loose fit on the guide rod -- whether through wear or purposely, I don't know. There is a small spring tensioned arm under the bearing, and its purpose is to take up the slack and keep the head tight to the guide rod.

I then tried sliding the printhead along the rod and the action was smooth.

I looked at the felt wipers -- they were basically petrified. So I put them in some hot water with dish detergent in it and worked them gently until they loosened up. I don't know if the stiffening was caused by congealed lubricants or ink, but it took awhile to get them pliable again. I blotted them on paper towels and quite a lot of black gunk (ink I believe) was blotted out. They gradually became light in color -- like felt should be.

I then oiled them with Tri-Flow (available at bicycle shops) and reinstalled them under the bearing clips on the printhead.

These clips must be oriented correctly with the round notch toward the front of the printer. (I made this mistake on reassembly and had to rotate them again when they later blocked the head movement when the paper rollers lifted).

I believe that the hardened felt wipers were the cause of the earlier printer malfunctions. They acted as shaft locks when they tilted in their clips during fast traverses. A slow traverse using a manual push wouldn't cause this to happen, so the problem was hard to figure out.

The happy result (so far) is that the printer is working again now, without lockups. I've done a bunch of test pages so far without a problem. I'm waiting now for the new carts to really test it out.

By the way, this HP 1120c printer is well built, in my opinion, and I've been through a lot of its mechanics by now. The carts are big (42 ml on black and 10 ml ea. for the three colors) and the jets are renewed every time you put in a new cart. That may seem wasteful mechanically, but it does mean that I will have basically new jets. I will refill after that, so there is no real mechanical waste.

The rollers are all substantial and the rubber is good, even after all these years -- the mechanisms are all heavy duty and well made, as far as I can see. There is mostly metal in this machine -- except externally -- that part is a little flimsy and aged. The cleaning station drum has about 4 different tools on it, including a suction purge, I believe. It all looks good and well designed.

I would say that the biggest problem for these printers by HP is that there is NO service manual, NO spare parts, NO responsible maintenance user instructions (wipe the exterior with a damp cloth -- duh... but NO mention of oiling the felt wipers, for instance), and NO useful support.

NOT that the machine itself is poorly designed or built. It's just that if it doesn't work, meaning it just stops and blinks, for most people, the only recourse is to throw it away. No one knows how to fix them, or with what parts. What a waste of something that could last 20 years with a little maintenance and replacement parts.

 

[RWP]

Glad to see you are making progress, both in locating a suitable printer for direct printing to sheets of balsa as well as using your sound technical skills to correctly diagnose and repair a printer without a service manual. Thanks for sharing your experiences in tearing into this printer; you have very good technical writing skills.

All the printers I have use what appears to be white lithium grease to lubricate the print head carriage support/guide shaft. I have no idea if these use bronze bushings, but that would be an ideal match. Nylon bushings tend to be best suited for use where no lubricant is used and lubing them will usually lead to binding. Great observation about the died out wiper seals being the cause of the drag. I normally would use a silicone lube to restore these but not next to a different lube type (like white grease on the shaft). Good to know that the bicycle lube worked well for you. Next time I encounter a dragging print head carriage I'll know what to check for...

 

[vtjet]

HI RWP,
Thanks for the kind comments. I hope this will help someone else.

I did try white lithium grease before I removed the rod and printhead, and results were a lot worse. In fact it would hardly move from home, even when just opening the cover to simulate a cart change, before flashing the lights.

I also cleaned that off and tried Break-Free, as well as the Tri-Flow. These are progressively lighter oils -- the last two contain Teflon. I got better results -- a few partial pages printed -- with these. The grease definitely caused more drag -- you could feel it when sliding by hand.

I might be wrong about this, but I don't think felt wiper/oilers are usually used with grease -- usually felts are saturated with oil. I don't think grease wicks well. so I don't know why it would be used with felt. Maybe there are lighter grades of grease than the one I used. I'm sure all rhis is variable.

The bronze bushes on the 1120c looked sintered -- surface was grainy looking. If so, and they were oilite type, the lubricant they are impregnated with is approx 20 weight oil -- I know because I have cast sintered bearings into aluminum castings, and had to remove the impregnated oil before casting, since it would flash in the flask. This can be done by soaking in a solvent like lacquer thinner. I then had to re-lube the bearings after casting, and found a bearing manufacturer who described what they used and how to reapply it, and it was 20 weight oil that they recommended.

I do know that some printers (I believe my Canon S600 does, for instance) do use grease on the guide rod. It probably varies, depending on the printer design and the specific grease.

Anyway, I'll use the Tri-Flow for now, unless I run into more problems, or firm information. HP, are you reading this?

Do you folks look at forums like this?

If so, you know, we're not the enemy. We'd actually like to help you produce sound marketable sustainable and economical products. It's possible to have a profitable business model along those lines. We'd buy those products if they lasted more than 3 years, you maintained models more than 1 year, stocked parts and manuals, and the consumables were fairly priced.

How about getting rid of carts altogether and adopting a mini CIS as standard methodology. Then just produce superior inks at competitive prices. We'll buy them. We'll buy parts, too. And talk you up instead of down.

The boom is over. People want value.

 

[RWP]

HI RWP,

I might be wrong about this, but I don't think felt wiper/oilers are usually used with grease -- usually felts are saturated with oil. I don't think grease wicks well. so I don't know why it would be used with felt. Maybe there are lighter grades of grease than the one I used. I'm sure all rhis is variable.

The bronze bushes on the 1120c looked sintered -- surface was grainy looking. If so, and they were oilite type, the lubricant they are impregnated with is approx 20 weight oil -- I know because I have cast sintered bearings into aluminum castings, and had to remove the impregnated oil before casting, since it would flash in the flask. This can be done by soaking in a solvent like lacquer thinner. I then had to re-lube the bearings after casting, and found a bearing manufacturer who described what they used and how to reapply it, and it was 20 weight oil that they recommended.

I re-read your previous post and realize I misread (mis-remembered is more accurate) your statement regarding the wiper material being dried out felt. For some reason I was thinking of a dried out rubber or synthetic rubber-like seal that normally would respond better to a silicone lube. Light oil certainly is felt's best friend.

HP's use of a sintered bronze bushing helps explain why the lighter viscosity bike lube you used worked better than white lithium grease. Sintered bronze and graphite impregnated bushings/bearings are ideal for reliable operation in dusty conditions (paper dust) like fan motors and clothes dryer exhaust fan blower assemblies. I'll bet that printer of yours will now work reliably for quite some time -- at least the print head carriage section...

 

[vtjet]

Well, the remanufactured cartridges were both defective.

I got them from a place called databazaar.com

The cartridge problem light started blinking when I put either one in (HP-45 and HP-23 equivs). I took them both out and replaced them with my old HP carts, and the printer worked again. Then I took the non-OEMs out and shined up the cart contacts with an eraser. This seemed to work with the color cart (HP-23) but not with the black cart.

I tried printing with the color cart and my old black cart. Really bad color -- what was there was REALLY washed out, no yellow and serious banding. I did a surface wipe cycle in the printer, and a cleaning cycle. Also tried setting the cart head on a warm moist filter paper pad for ten minutes -- actually did that after the first trial when ONLY magenta was showing. Eventually got cyan, but yellow almost totally absent.

I'd had enough. I don't want to mess with a "re-manufactured cart" I didn't run a purge cycle on the printer, because this uses a lot of ink according to HP. I noticed the Databazaar guarantee says the carts must be 70% full on return, and when I shook the cart I could tell it wasn't totally full to begin with.

So I've contacted the company for an RMA. I don't want replacements if the carts are this bad.

I've re-ordered carts from another vendor.

 

[vtjet]

Well, I just got new carts from LD Products, and they work great. The printer now works perfectly!

Now that I have good carts, I want to refill. They are HP-45 and HP-23 compatible carts. The inks needed are 4 color: CMY and pigment black.

Can someone recommend a good brand/supplier of quality bulk ink for HP printers?

Thanks!