HP 97 Printer



#2

Hi all,

the printer in my HP 97 doesn't work very well.
The symptoms are:
- It prints quite well, but the paper doesn't advance like it should.
- If I pull the paper then for a while (about 2 lines) it keeps going, advancing correctly, after that it just stops.

I find this very strange, can anybody give me an hint how to fix it? For what I see, the dented wheel are good, can it be the motor?

Regards,
jbssm


#3

Sometimes a drop of machine oil (sewing machine oil) on the paper advance rod will do it. If not used for a long time this becomes dried out. Possibly someone else recommend a different type oil.

Best


#4

Thank you for the fast answer, but can you specify better what is the "paper advance rod" ?

Regards,
jbssm

#5

Thank you all very much ... it worked :)

#6

It is a very common 97 printer problem. Oil does not help, only makes things worse as it is usually a lack of friction that causes the problem, not the other 'way round. Have a good look at the shaft that is rotated by the motion of the print head moving back and forth. That shaft has two "tires" at the ends that contact the paper and push it upward when the shaft rotates. Those tires usually have flat spots on it from sitting in one place too long. When those flat spots come around in rotation, the paper doesn't advance.

A very simple solution from the 97 man himself, David Smith, is to hang a large paper clamp on the end of the paper and drape it over the edge of the desk. The extra weight of the clamp will pull the paper through the printer as the tires advance, even over the flat spots. Easy, but maybe not up to your technical standards.

So, if that's not an acceptable solution, you are looking at a complete disassembly of the printer to make it right. If you're not mechanically inclined and handy with small snap rings that like to shoot out your fingers and into parts unknown in the next room, this is not for you... even if you do want to tackle this, depending upon the condition of the of two driving "tires" this may or may not work:

Tear the printer down to get the shaft out - some help can be found in the 97 service manual on the Museum CD set. The worm shaft and the two pin shafts that the head rides on must come out. Once you have the paper advance shaft out, sand the tires round again with 150 grit or so sandpaper. Don't go overboard here, only take off enough to rough up the circumference and make it somewhat more even and the transition to the flat less pronounced. Clean all the accumulated goo off the worm shaft, clean up any thing else sticky and icky and put it all back together and enjoy.

If the tires are really bad or cracking apart, I've been able to make a reasonable repair using rings of vinyl tubing glued in place after cutting away the old urethane. That would be an extreme case and not something to do first time around. You can also canibalize an 82143A printer as they use the same shaft but understand your parts donor may have the same problem. Later 82143A's had black tires instead of the original natural color urethane, those IMO seem to hold up better.


#7

Hmmmm, well just fixed an HP82162A yesterday with a single drop of oil. This one was half line feeding 80% of the time. The HP82143A manual specifies the lube points, one drop of machine oil (HP instructions). The ratchet needs some oil or it don't ratchet, don't hurt the cam either. Sometimes they dry out. Notwithstanding flat tires.

#8

The slipping paper is a combo of flat spots on the drive rollers, hardened drive roller rubber, and modern paper is thinner and slicker than the original stuff.

Besides sanding down the drive rollers, I have been painting them with a thin layer of new urethane. This has worked VERY well. I have also built up complete new rollers with the stuff.

I use a synthetic urethane polybutadiene rubber called HTPB R45-M. It is used as a binder in solid rocket motor propellent. It uses an isocyanate type curative like Isonate 143L, PAPI94 or MM103. A couple percent castor oil in the brew promotes cross linking and more natural goodness. You can get the stuff at FIREFOX-FX.COM Beware the curatives are nasty stuff. Some of them also crystalize out below room temp and need to be heated in a water bath to redisolve. They also have a limited shelf life. I always test my curatives on a small batch before doing any real work with them.

CP Technologies (SPACE-ROCKETS.COM) sells a more user friendly curative called Rubinate. They also have a thinner R20 resin, but I prefer the thicker R45M or R45HTLO. Aerocon Systems is another source.

After painting the drive rollers, I tape them vertically to the edge of a table to cure for 24 hours.

#9

jbssm wrote:
> the printer in my HP 97 [...] prints quite well, but the paper doesn't advance like
> it should. - If I pull the paper then for a while (about 2 lines) it keeps going,
> advancing correctly, after that it just stops.

As the others have suggested the problem is prob. that the two soft wheels on either side of the carriage cannot get enough traction on the paper.

To get a better look at what is happening, remove the transparent cut guard (rectangular piece of plastic that tears the paper when you pull it), and look closely into the mechanism. On the end far away from the print head, you should be able to see the wheel that pulls the paper through the mechanism (thats the left-hand wheel, the right hand is covered by the print head when the head is in its home position).

Looking at the wheel, press the PRINTx or PRINT:SPACE. Does the wheel slip against the paper? If so the problem is with the wheels. If the motion of the print head is sluggish, or it does not quite return to the home position, then you have a problem with print head mechanism (in this case lubricating the mechanism may fix it).

If the problem is with the wheels do not use any oil!!!!!

Assuming its the wheels, you may be able to get them back to life without disassembling the machine.

Get very fine sandpaper and cut a thin strip 3mm wide by about 20mm long. The piece should be wide enough to cover the width of a SINGLE wheel (you will treat each wheel separately).

You do not want to get sand paper in front of the moving print head!!!!

Then you remove the paper and insert the strip so that it sits between one wheel (start with the left hand wheel) and the backing plate. Holding the sandpaper so that it does not move, press the paper advance button on the side. The printer will complain a bit, but it should move the wheel against the sandpaper. Press the ADV button a couple of times (so that the entire circumference of the wheel scrapes against the sandpaper.

Repeat with the right hand wheel being very careful to stay clear of the printhead.

Use ONLY VERY FINE SANDPAPER. You do not want to destroy the wheels, just make their surface rough.

**vp


#10

Would you consider 240 fine enough, or is necessary to use paper like the 600 or 1000 used for car paint repairs?

Andreas


#11

I used 600 sandpaper, because that was the finnest I had around.

#12

When I prepare a printer cam, I remove it from the machine, touch up the edges of the flat spot manualy, and then roll the cam back and forth on a sheet of fairly coarse sandpaper (like 120 grit). You need to put some sideways tension on the cam to keep the clutch open.

You can then try a methyl salicylate based rubber restorer (GC Chemicals Ruber ReNew) or slot car wheel traction fluid, but I have found it does not last long. That is why I have been coating the rollers with HTPB urethane.


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