HP 97, OK I cracked the print head..



#13

Now what?

I read that this was a possibility so I was extremely careful... at least doing what I thought I needed to be careful about. The thing slipped nicely between the clamping bar, slid nicely under the platen, was not cocked or misaligned as nearly as I could see with my magnifying glass and flashlight, and yet "Snap" when I tightened.

What's the best shot at getting a replacement? A 82143A printer?

Assuming a replacement is available, what is the secret for reinstalling this thing?

Grrr!

Edited: 21 Mar 2010, 10:36 p.m.


#14

Hello Ed,
unfortunately the thermal printer head of the 82143/82162 printers aren't compatible (80 ohm Vs 11 Ohm of Topcat printer series). You must search another Topcat printer if you want replace yours.
Sorry for the bad news.

Regards

Ignazio


#15

Thanks, Ignazio. BTW, what is a "topcat" printer? I've seen the term used here but don't know what it means exactly. I assume it refers to the particular printer used in the 97 and probably others, but I don't know which others.

Do you know what I might have done wrong? I did look at the head with a magnifying glass before tightening and all look OK to me. IOW it was not cocked in the slot. I held the platen out of the way so I could push the head in till it registered against the opposite side of the carrier, leaving the top end flush with the carrier.

Ed


#16

Sorry to here that Ed.

The specs are different and the HP 91, 92, 97S and 97 are the "TopCat" family.

Cheers, Geoff

#17

Hello Ed,
Geoff has just answered to your first question about the Topcat calculators.
Regard the second question I must say that I haven't understood so well how do you have tried to assemble the print head.
I prefer to assemble the paper feed cam with the carrier and the print head, not over tighten the two screws that hold the clamp, then install this assembly in the body of the printer.
And after mounting the lead screw, the two rod and all the other parts, as the last thing reconnect the printer cable contacts to the PCA using a thin metal foil 24 mm wide.
Let me know if my English is understandable and if you prefer some pics too.

Regards

Ignazio


#18

Thanks, Igzazio. I understand your explanation of your method... basically you're installing the head on the carrier before installing things into the housing. I reversed the disassembly procedure given by Tony Duell in his Sept 2005. This makes the print head installation on the carrier last, after everything else is in place. But, I don't see why that should make any difference as long as the head is properly positioned in the carrier.

Does anyone know exactly what typically causes the fracture? For example, is it:

a. Improper positioning in the slot it's supposed to register in on the carrier?

b. The head being pushed too far or not far enough into the carrier?

c. Simply overtightening?

d. The head interfering with the cam?

In other words, just saying "be careful" doesn't help if one doesn't know what to be careful about.

I haven't removed it yet, but I will now and see if there any clues.

Ed

Edited: 22 Mar 2010, 10:34 p.m.


#19

Looks like I might have cried wolf too soon. I took the head off the carrier and it's all in one piece and no cracks are evident with a magnifying glass. I won't know for sure till I get it all back together, of course.

I also removed the carrier from the slide rods etc. so I could see exactly what it means to have the head registered in the carrier. There is a lip on the carrier where the business end of the head goes. Obviously, the head must be within its channel and registered against this lip. I think I may have had it slightly up over the lip and the snap I heard while tightening it was when it managed to snap down where it belongs.

It would be nice if the head could be installed on the carrier before installing it on the lead screw and cam. However, there would be a problem getting the cam through the carrier. The only way that could be done would be to pull one of the rollers off, slip the shaft through the carrier, and then reassembly the cam assembly in situ, so to speak. Triky biz.

Another thing I noticed is it looks like there was some kind of thread locker on the screws that lock the head to the carrier. has anyone else noticed this? That would make it unnecessary tighten them so much.

Ed


#20

Ed,
If you have a multimeter or a Ohm_meter (?), you can verify if the resistance between the ground and each other seven tracks is about 11 ohms, measured to the connector at the other end of the flat cable. If this is not true for one or more of the contact, your thermal head must be throwed away.
You can assemble the carrier with the paper feed cam and close it with the print head and the clamp. The two screws must be installed with a drop of thread locker on the tip. You must remember to lubricate the rod and the lead screw after intslling them on the body of the printer.

Ciao

Ignazio


#21

Quote:
Ed,
If you have a multimeter or a Ohm_meter (?), you can verify if the resistance between the ground and each other seven tracks is about 11 ohms, measured to the connector at the other end of the flat cable.

All are about 10.8 ohnm, so I guess I dodged the bullet! Since I have not removed the cable from the connector I did these measurements at the PCB pins.

Quote:
You can assemble the carrier with the paper feed cam and close it with the print head and the clamp.

I figured that out after I wrote the last note. that's what I will most likely do. In retrospect, its the only way one can really see that the head is properly seated at the "business end," if you understand that term.

It also occurs to me that by removal of one roller from the cam shaft the during disassembly one could slip the carrier/head assembly off the cam so the rollers could be worked on without even disturbing the print head. have you tried that?

Quote:
The two screws must be installed with a drop of thread locker on the tip.

I'll use the kind that is less strong so it will be possible to remove them if needed.

Quote:
You must remember to lubricate the rod and the lead screw after intslling them on the body of the printer.

What would you recommend that I might be able to find? How about graphite powder sucn as used in locks?

Ed

Edited: 24 Mar 2010, 2:55 p.m.


#22

Ed,

Quote:
All are about 10.8 ohnm, so I guess I dodged the bullet! Since I have not removed the cable from the connector I did these measurements at the PCB pins.

I prefer to measure the resistance on the flat cable disconnected from the PCB. The value of 10.8 Ohm is correct.

Quote:
I figured that out after I wrote the last note. that's what I will most likely do. In retrospect, its the only way one can really see that the head is properly seated at the "business end," if you understand that term.

I don't understood "business end", can you translate in other words? Thanks
Look at this image, thermal printer assembled with carrier and paper feed cam.

and at this, after installing on the printer body:


Quote:
What would you recommend that I might be able to find? How about graphite powder sucn as used in locks?

You must lubricate the lead screw and guide rods with lightweight machine oil (sewing machine) and a long nosed applicator. Apply one drop at each bushing, and one or two drops along the screw itself and each guide rod. Then turn the main gear a number of time to distribuite the lubricant.

I hope this help.

Ignazio



#23

Thanks, Ignazio.

"Business end" of something is slang for the end that does the work. I was looking for an easy way to refer to the end of the print head that actually does the printing.

OK, that clears up the lubricant issue. I believe the exploded view of the printer in the Service Manual shows these points. I've seen posts recommending "plastic lube" for the plastic parts such as the cam, but I wouldn't know where to get such a product.


#24

Ed,
thanks for your explanation about the " business end". Let me know how your work goes ahead with the printer.

Regards

Ignazio


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