HP-41 HP82143A printer repair.

[Papymouzot]

Hi everyone,

I have taken maybe a couple of months ago a big box from the basement, inside HP-41 fullnut (dead) card reader, lots of cards with lots of programs. Lots of manuals, some modules and a printer. Missing : a 41-cv, it’s battery, lots of modules. I don’t know where they could be ??

I was like a kid… a lot of memories from 1980’ when I was studying and enjoying this wonderful calculator. I wished to be able to read the programs, print them if at all possible and check what I was able to do back then, when I still had a brain ! ??

I purchased from a very nice guy in the USA a 41cx half nut with some modules (x-memory, advantage, math/stats and games…

Tried my card reader… malfunction ??
Bought another one on EB … card err bought another one … card err
Learnt about the gummy wheel issue and attempted to repair them. One still gives malfunction (my original one) and the one now works… the other one still card err

I tried also the printer. It gets recognized by the 41 but does nothing… Somebody told me I needed a good working battery pack in order to be able to print… purchased 4 NiCd from AE and rebuilt the pack two days ago… piece of cake after having rebuilt the 41 battery pack…

So, new batteries, fully charged… tried to print… printer error, tried paper advance… nothing…

Ok, let’s open the beast.

Amazing… dust in it… I tried reading the service manual, a shame the pictures are so bad quality…

Removed the motor, tested it… it worked… yes
The little belt was in good condition (these products were really great quality back then !! )

Ah ! The axis with the two wheels which are on each end didn’t want to move. So I cleaned these two wheels which are not anymore 100% round after 40 years in a cardboard box. The paper advance mechanism now worked.

I lubricated the worm gear, and removed the print head to clean it… good idea, it was filthy.

I tried turning the printer on… this time the head moved and the mechanism to pull the paper wanted to work but the paper got stuck… I tried to understand where and why ? The paper stopped at the print head position

I thought that I didn’t put the printing head back in place properly… I then removed the head and tested again…. The paper stops again, right at the limit where it is aligned with the little piece of fabric (Teflon ?) (without the head)

I stopped there, thinking I betta ask for advice on the forum.

Is this piece of fabric supposed to be glued on the copper part ? Mine isn’t.


Any idea why the paper stops there ?

I look forward to reading your comments !


Charles

[AndiGer]

Did you remount the print head correctly?
It sits inside its frame. You must look from above and see the white from the head through the little windows in the head carrier. The head must sit regularly and flat inside the frame. To mount it properly you have to press back the platen that is in the upper part near the fabric. Then it (EDIT: the print head) snaps into place.
Picture in g) and k), l) in section 7 on page 22 of the Service Manual. The pictures are very good if you load from https://literature.hpcalc.org/items/410
No. 17 - platen - on page 7-5.

Andi

[Hiwi]

Hi Charles,
the fabric is not glued, did you disassemble the fabric? May be it is not assembled correct, the fabric should cover the small axle, a bit difficult to explain. Thje small axle schould be unter the fabric. Sometimes the fabric is torned or damaged.

I most cases the paper advance is not working any more. There are on both sides small transport wheels which are worn out or dried out or malformed over the years.

This is nearly the same as with the cardreader.

Ralf

[Papymouzot]

(04-02-2024 03:25 PM)AndiGer Wrote:  Did you remount the print head correctly?

Well, the answer is no !! First time yes, but as the paper advance seemed to stop at the head I removed it… big mistake !!! Without the printing head circuit, the head carrier cuts the fabric !!! I damaged it when the printer did try to do a paper advance…

(04-02-2024 03:25 PM)AndiGer Wrote:  It sits inside its frame. You must look from above and see the white from the head through the little windows in the head carrier. The head must sit regularly and flat inside the frame. To mount it properly you have to press back the platen that is in the upper part near the fabric. Then it (EDIT: the print head) snaps into place.
Picture in g) and k), l) in section 7 on page 22 of the Service Manual. The pictures are very good if you load from https://literature.hpcalc.org/items/410
No. 17 - platen - on page 7-5.

Andi

I’ll download this manual again then, thank you !

By the way, at the moment my issue isn’t solved… I’ll check again later…

[Papymouzot]

(04-02-2024 03:45 PM)Hiwi Wrote:  Hi Charles,
the fabric is not glued, did you disassemble the fabric? May be it is not assembled correct, the fabric should cover the small axle, a bit difficult to explain. Thje small axle schould be unter the fabric. Sometimes the fabric is torned or damaged.

I most cases the paper advance is not working any more. There are on both sides small transport wheels which are worn out or dried out or malformed over the years.

This is nearly the same as with the cardreader.

Ralf

I didn’t disassemble the fabric but the print head, and I did a good job at damaging the fabric. I managed after some efforts to « repair » it, the future will tell me if I did a good job at this !

The wheels on each side are not perfect but they aren’t too bad.

More this evening my time

Thanks for your suggestions and comments

[Papymouzot]

Quick news… I had little time this evening… my fabric repair seems to work. When I have the print / motor assembly out of the printer case / electronics and I apply 3.3v onto the motor the print head moves to one side without problem, when I invert the polarity it goes to the other side. The paper advance mechanism seems to work fine.

When I reconnect the unit int the printer it is a different story. The head moves to one side and one second later the motor stops and next time I try to print I get a printer error message on the 41. End of story….

The inside of my printer is different from what I can see in the manual, it would be too easy otherwise ??. I’ll post some photos if one is interested.

I’ll keep investigating tomorrow, your suggestions will be appreciated

Charles

[Papymouzot]

Hello !

Some progress this evening !

I actually thought that it was working now…

As long as I print on the right hand side of the paper the printer works fine, for example, in mode trace, I key 1 enter 1 + and I get the correct printout. Paper advance works fine, print is clear on my 43 years old paper ??

But

When I wish to print something which will be left justified, it starts and stops quickly… and I get a printer error, for example when I execute PRREG or PRP…

I will try to include some photos…

When I get a Print Error, the only way out is to switch the printer off then on again

Any ideas ? ?

[Papymouzot]

Photos







If I try to print the same thing, justified to the left, at the beginning, 1 or 2 characters aren’t printed… works was initially « it works »

But, if I try to print the same multiple times, of course I am obliged to switch off/on the printer in between each attempt, I get more and more of the first characters being printed until they get completely printed, but I still get print error on the 41

It looks like the printer is missing the information about its home position for the head, but my printer hasn’t a sensor for this like shown in the service manual.

[Hiwi]

Hi,
every printer 82162, 82143 & HP97 have homeswitches, they are adjustable. Should be connected to the white cables. Red cables are for the papersensor.
Ralf

[Hiwi]

I have noticed, that you have done printing without the transparent plastic cover. Is the result better when it is installed, apart from the error on your HP41?
Ralf

[teenix]

Have you lubricated the points marked in the service manual, these are where the rotating shaft ends sit in bearings. If these dry out the printer mechanism becomes finicky and may distort the printout. I use tiny drops of hair-clipper oil. They may need disassembly and cleaning prior to oiling.

cheers

Tony

[Papymouzot]

(04-05-2024 01:14 PM)Hiwi Wrote:  Hi,
every printer 82162, 82143 & HP97 have homeswitches, they are adjustable. Should be connected to the white cables. Red cables are for the papersensor.
Ralf

Hi, as I have said before, my printer hardware isn't the same as the one pictured and described in the service manual. There isn't a home sensor.... no switch, nothing..., no white cables. I can see them in the service manual and I could also see them in pictures found on the internet but they aren't present on my printer. I only have the paper sensor. The encoder wheel is also on the other side of the print/motor unit, not on the pulley.

[Papymouzot]

(04-05-2024 10:25 PM)teenix Wrote:  Have you lubricated the points marked in the service manual, these are where the rotating shaft ends sit in bearings. If these dry out the printer mechanism becomes finicky and may distort the printout. I use tiny drops of hair-clipper oil. They may need disassembly and cleaning prior to oiling.

cheers

Tony

Hello, hello..

Yes I have lubricated the points marked in the service manual. I have cleaned the rubber wheels on each side which were "glued" to the two plastic wheels. The most difficult cleaning task was the paper advance mechanism which wasn't working, all glued together, probably with a mix of dust and oil...

The paper advance works well now, printing is clear and precise, at least for a printer which is so old. Printing isn't distorted. Printing on the right hand side of the paper is ok. My issue is when I print something which is left justified, only the first line is printed, with missing dots at the leftmost side. once the first left justified line is (partially) printed I get a print error message... until I cycle the power on the printer

[Papymouzot]

(04-05-2024 01:39 PM)Hiwi Wrote:  I have noticed, that you have done printing without the transparent plastic cover. Is the result better when it is installed, apart from the error on your HP41?
Ralf

Hello, the back plastic cover was installed on the printer. It seems that there was a little piece of plastic in the front, I can't remember, if there was one in the front, it is missing today There was one probably, as there is no way to cut the paper today

I have tried printing with the printer being completely opened and there is no difference. At first, when finally I could print and it was clean I thought that I was done.... and reassembled the printer completely.... it was only by then that I tried printing left justified items.... sad sad sad

[AndiGer]

Hi Charles,
Maybe your print head also runs into the left wall?
Did you read this thread till the end?
https://www.hpmuseum.org/forum/thread-7500.html

Andi

[Papymouzot]

(04-06-2024 06:52 AM)AndiGer Wrote:  Hi Charles,
Maybe your print head also runs into the left wall?
Did you read this thread till the end?
https://www.hpmuseum.org/forum/thread-7500.html

Andi

Hello,

Right: my printer, Left: photo taken from the net



There is nothing at the home position to detect the print head..

The encoder on the left hand side of the print/motor unit must be working as the printer works fine when printing right justified items. This wheel is supposed to give information to the printer about where the head is.

I am lost !

I opened the printer to take the photo above, and when the printer is open, printing works...when I close it again it doesn't...

Something new. to investigate !!!

[AndiGer]

I saw that kind of printer arrangement in an HP-82162A only.
My guess: the clear something LHS of the encoder is the foto transistor that does the same job as the one that is on the RHS in the picture taken from the net.
But I don‘t know how the home position is detected on yours. Nor do I know why it prints fine when open. Has to do with light I guess …
Andi

[teenix]

The encoder wheel is most likely used for speed control feedback. I cannot see any parts in the circuit for electronic feedback. I can't think of how it can be used as a position sensor without a 'home' reference. For example, at switch on, the print head can be anywhere in its length of travel and the processor will not know where.

Your circuit board looks more modern compared to the left picture, so there might be a home sensor mounted on the main circuit board.

Check the encoder sensor for dirt that may be covering the led/detector facing the wheel. It is also possible the unit is faulty.

cheers

Tony

[Papymouzot]

I believe that the home reference is set at switch on, if I move the head manually by rotating the encoder wheel when printer is off, and I switch it on afterwards, the head goes to home position (far right) then motor stops.

The issue could have been dirt, I blowed on the sensor, and now the printer seems to work... I'll see if this lasts.

Nobody would have photos & dimensions of the little transparent plastic cover which should be in front of the paper ?

Thank you all for your help and comments...

The main usage for that is probably to be able to cut the paper. I can't find it and would like to draw one and 3D print it. Of course I can make measurements myself, but I'll be happy to know the shape it should normally have.

[vassilisprevelakis]

Hi,

I have had some success using bits cut off from the plastic cover of CD jewel cases
for the HP-85 tear bar (https://www.series80.org/Articles/PaperTearOffBar.html)

Here are the pictures for the HP 82162A printer (the HP-IL version of the 82143A - it should be the same part).



Top View    
View from the side    
Note the ruler is in cm (!)

Good luck with the repair.

Vassilis
http://www.series80.org