82240A Printer Problems/Questions



#12

Anyone know what might cause the 82240A to stop printing? All mechanical functions appear to work, including the appearance of printing when IR print commands are sent, with paper advance and head movement...just no print on the paper.

Also, anyone know how to open this up? Do the feet come off to reveal more screws? I found two in the battery compartment and that was all.

Lastly, anyone know what the difference is between an 82240A and 82240B printers?

Thank you very much! :-)
Sam


#13

The difference between the A and B, AFAIK, is in the character set. I believe the B was developed to satisfy a new standard for international character codes.


#14

Hi;

Ellis is right about the set, and also there is a small difference between both when printing characters. The bottonmost line of each printed line in the B series is a blank line, allowing better readings. Grafhics is the same.

Tell us: does the printer passes OK in the self-test? Say, switching it ON whille you keep ADVance key pressed results in the printing of all character set? If so, have you tried using another calculator?

Also, if the self-test is OK and you don't get printing, try to open it (yes, there are four screws under the rubber feet) and check for bad soldering in the IR receiver. I once had an 82240A, and I am not sure if it has a ON-indicating LED as in the 82240B; if so, open and close with care.

Hope it helps.


#15

Self test appears to run, but there is no print on the paper at all...just goes through the motions.

I'll have to try prying the feet off to have a look in the inside... maybe the fault it visible... or perhaps a matter of unplugging and replugging some connectors.. if not, I guess it may just be a "parts" item...

Thank you!
Sam


#16

I've never opened mine, but there is a good chance that the print head is connected to the PCB by a flex cable which might have come unplugged from its socket (good case) or flexed in two (bad case). There is an article in the museum repairs section that might help:
HP-97 printer ribbon repair

#17

One obvious thing to check is that you have a roll of thermal paper installed, with the proper side facing the print head. I bought two "dead" machines for real cheap. They had plain paper installed... worked fine with thermal paper.


#18

Boy is my face red... the thermal paper was installed backwards!! :p

I could have sworn I tried it both ways...oh well, hey thank you very much David and Tony both for your dead-on diagnosis to the problem!!

Now my only complaint is that with the contrast slider set dead-center, the print is too faint. With it set all the way to the right, its better, but still not great. Print-outs from my 82143A printer for the 41C series is far better. I wonder if its the paper? I have NCR paper in the 82143A (which I'm told gives better output than the HP paper...). I'll have to try the NCR paper in this printer.

Thanks again!! :-)
Sam


#19

Well, for what it's worth, I don't consider the contrast from my 82440B (using HP paper) to be very good either. I have the intensity slider on 'max' all the time,
it's readable, but I've seen better. I have considered fiddling with the RC network round the constrast pot, but
I am worried about driving the printhead too hard and burning it out. So I put up with readable, but not great, printouts.


#20

Do you guys have batteries in your printer, even when you are using it on AC? It makes a big difference. I am the original owner of my 'B' printer and it has had very little use, I'm only on the second roll of paper. With NCR paper, no batteries, and slider all the way to the left I get readable printing (individual dots clearly evident). With batteries, I get very dark printing (at least when I look at them side by side). With the slider all the way to the right I get pretty much the same results with or without batteries, both darker that with the slider to the left with batteries. But maybe the paper is "saturated" for want of a better term.

BTW, has anyone else noticed the family resemblance between the 82240A/B and the HP56 model in the "HP Design Studies" section? The overall shape as well as the buttons and sliders. (Please let me know if it is an imposition to link a pictue to the Forum. I picked the smaller of two pictures.)

#21

I have found the NCR paper to be very good at giving nice print quality in marginal machines. Most if the HP paper is well past its intended lifetime and gives very poor performance. BTW, I know one guy who has run well over 50 rolls of the NCR paper through an HP97 with no problems at all.

#22

I've only ever openned up a 82240A once, years ago. I know rather more about the 'B'. I do remember there are electronic differences between the A and the B (particularly in the IR preamp circuit -- both use chips
designed for TV remote control sensors, but different chips). So some/all of what I say below may not be applicable to the 'A' -- it all comes from notes I made on the insides of my 'B'.
Yes, there are screws under the feet. And inside the battery compartment. With those out, the top comes off. Don't loose the switch actuators.
The printer mechanism is held in by 2 small screws. It connectes to the logic board by 2 connectors. One carries the motor/tacho/home switch signals. The other is the tapewire from the printhead. On the logic board there's the IR input circuitry, some PSU stuff, a standard microcontroller (an 8050 in the 'B') and the printhead/motor driver chip. The printhead is essentially driven by one 8 bit port on the microcontroller, one bit per heater. The intenstity slider is a pot, read out using an RC network and a couple of port pins on the microcontroller.
If you're getting no printing, first check you're using HP thermal paper and that it's in the right way round. If so, then take the cover off and unplug the tapewire from its connector. One end trace is common, the other 8 are the other end of each heater. Check the resistance from 'common' to each of the other pins (expect a few ohms). If they're open, then you've got printhead or tapewire problems.
Then check the intensity pot and the surrounding components. I have no idea what happens if it goes open-circuit, but it might well result in no printing.
Then check the printhead driver chip. Trace the PCB tracks back from the printhead connector to find it.


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