HP-97 Printer Malfunction

Hi All,

I've got an HP-97 with a malfunctioning printer. Everything on the calculator works fine, but as soon as you try to execute anything involving movement of the printer (printx, paper advance, or even removing the roll so the printer tries to take up new paper) the screen flashes "Error" and the machine becomes non-responsive (CLx does nothing to reset it, the error condition remains as long as the printer is trying to operate).

When I first got the machine, I noticed that when the roll of paper was removed, the printer would try to take up a new roll for some time. If no roll was inserted, the printer would stop and the screen would display error. Otherwise the printer worked fine.

Now the printer is completely non-responsive. However, if the print head is manually moved over to the left side of the paper, the print head will be moved home as soon as the machine is turned on, but nothing else happens and "Error" flashes on the screen.

There is nothing obvious that could be wrong (loose wires, broken solder joints, etc.) so I'm not quite sure what the problem is.

Any help anyone could give me would be very much appreciated.



I presume this behavior occurs when you have paper in it, correct?

Does it behave this way with the printer switch in the MAN position?


Not exactly,

If paper is in it, the calculator works fine, but as soon as a print instruction is issued, it goes into the error loop.

It does report an error with the switch in the MAN position, yes.



I haven't seen that symptom before to have an idea on the fix.

Have you checked to see if the paper present switch is correctly connected to the sub pcb?

Edited: 18 Nov 2013, 7:36 p.m.


Yes, that's connected like it's supposed to be and shows continuity without paper and an open circuit with paper present.

Anyway, I contacted the guy I bought the calculator from and he said he has an extra printer he's going to send me! Hooray! If the one he sends me works, I'll still keep the defective one around for parts (motor, roller cams, etc.)

I also found out that one of the transistors on the sub-pcb is bad. Both of them are marked with a Motorola "M" and have the numbers 530393. One tests properly on the diode setting of my multimeter (ie ~ .7 V across the Collector-Base junction and Emitter-Base junction) but the other one (closest to the motor power wires) has an open Collector to Base junction.

I'd be happy to order more of these transistors and replace the bad one to see if it improves anything, but a Google search for "Motorola 530393 Transistor" turns up nothing useful

The three 14-pin ICs are numbered 1858-0044 and are also Motorola. A Google search for these DOES turn up something useful (ASAP Semiconductor may have these still).

Without a schematic or service manual, I have nothing to go on. I don't know what the ICs are or what they do.

I did, however, find a pretty neat HP digest (1976, I think) on the HP-97 and its printer. It states that if the machine ran out of paper, the printer would print right on the platen behind the paper. So, naturally, the platen can withstand the print head printing on it FOR72 HOURS! THAT'S SIX WHOLE DAYS!

HP really knew what they were doing back then.



Hi Dan,
the 1858-0044 chip is a four transistor array and drives the printer resistors and other things like the motor inverter.
I live in Italy and if you want I can send to you a -0393 transistor or a complete sub-PCB. Let me know how I can help you.




the platen can withstand the print head printing on it FOR72 HOURS! THAT'S SIX WHOLE DAYS!

Whoa! Your planet is spinning fast: here 72h = 3 whole days... ;-)


Edited: 19 Nov 2013, 10:08 a.m.



I thought about that right after I posted it!

Still, who's gonna let that thing run for 3 days straight?



I talked with the guy I bought the calculator from and he said that the two printers he was going to send me are also not working properly. For this reason, I think I will take you up on your sub-PCB offer.

I'd rather have the whole sub-PCB than just a replacement transistor because I have no way to test the sub-PCB I currently have, I only know that the one transistor is bad.

Do you have any thoughts on how I might prove the 1858-0044s are working? If I could just get a hold of a service manual for this machine, I'm sure it would have everything I need.

I think I'll have the guy I bought the calculator from send me the bad printers anyway. This way, I'll have a better chance of making one good printer out of three bad ones.

Do you know that your sub-PCB is operating correctly?

I sincerely thank you for your help, it means a lot to me.

Thanks again,


The service manual for the 97 is available on the museum DVD.


Hello Dan,
I need a little bit of time for check my spare sub-PCB for the 97's printer.

I'll inform you with a mail.




Sounds good, thanks!



I had thought about that, it may be a good idea to have all the manuals for every machine. I can think of times when it would have been nice to have them in the past.


Hi everyone,

I'm not sure how many people are still reading this, but I received some extra printers for my HP-97 and after changing out the bad transistor my printer had for a good one, it works!

The 0393 transistor near the motor power wires had an open Collector to Base junction. I'm not sure what caused this, but the calculator and printer work just fine now.

I would like to thank all who responded, it means a lot to me.

Thanks, I'm sure I'll be back soon,



As stated above, the printer works fine, but even after replacing the paper drive wheels following this thread and this slideshow, the printer still won't advance the paper like it should.

If the platen is held away from the print head, the print head it moves a little faster on the return stroke. Otherwise, the printer is very sluggish. If the paper is not helped along through the printer with a gentle pull, the motor moves very slowly, almost to the point of stalling.

The paper advance wheels turn against the white nylon rollers that are behind the paper when it is present, and the nylon rollers themselves turn, but it's as if there's too much tension somewhere.

Any advice?



Well as you may have discovered already the paper feed operates using a cam actuated by the print head motion. When the pint head moves to the left approximately 1/4 of its travel the cam is at it lowest point this allows a ratchet on the right side of the paper feed shaft to jump ahead a tooth and then when the print head returns to the home position the cam (ramp?) on the print head rotates up advancing the paper. So with power off does the lead screw that moves the printhead move smoothly? Make sure the gear teeth and lead screw are free of debris, also make sure the platen behind the paper is properly seated. What I would do is remove the print mechanism and pop out the idler gear between the motor and the lead screw and turn the lead screw by hand, you should be able to feel if there are any binds in the head movement. When you are turning the lead screw by hand you should also be able to observe the operation of the paper feed. When turning it by hand there should be almost no difference in the effort required to turn the lead screw anywhere in its travel even when the cam is riding up to advance the paper. If it is not a mechanical issue then perhaps the motor might be suspect. Also watch out for the plastic idler between the motor and lead screw it is very common for the plastic to degrade and the teeth strip off the gear.


Hi Paul,

Thanks for the input, I figured it was probably mechanical binding somewhere. I also have two other motors to try in the printer if that doesn't solve it. I'll check it out when I have more time in the coming week.




Glad that things worked out.

It would be interesting to know a industry standard part/replacement for this transistor. Does anyone know?


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