Re: HP-97 Printer Malfunction Message #5 Posted by Dan Lewis on 18 Nov 2013, 8:36 p.m., in response to message #4 by aj04062
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.
-Dan
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