Characteristics:HP 9871A printer


Dear Friends,
I'm looking for the pin assignment of the DC-37 port
of the above daisywheel printer.And for the data of the
two TO-3 case power transistors from the underside
of chassis of the printer (serial voltage regulators)
(probably blown out).
Any kind help from your party is much appreciated.
Many thanks in advance!
Best Regards,



The 98032A Option X71 parallel interface is used to connect the 9871A printer to a 9825, 9835, or 9845 calculator/computer. it might be possible to connect the 9871A to other calculators but the 9825 is the only model I am familiar with.

From the 98032A manual, pages 60-61, "9871A printer Interface":

(This manual is on/in CD6 in the latest Museum CD/DVD-ROMs. I can't look at mine now, my DVD drive is broken! but I have a printed manual)

printer 37 pin connector pin:printer signal name (98032A Interface Connector pin:98032A signal name) [wire color code]

12:CALC7 (A10:DO7*) [90], 13:CALC6 (A11:DO6*) [903], 14:CALC5 (A12:DO5*) [9], 32:CALC4 (A13:DO4*) [97], 31:CALC3 (A14:DO3*) [96], 30:CALC2 (A15:DO2*) [95], 29:CALC1 (A16:D01*) [94], 28:CALC0 (A17:DO0*) [93], 26:GND (A18:GND) [6], 9:CMD (A19:PCTL*) [1], 10:HLT (A21:Preset*) [3], 33:GND (A24:GND) [98], 27:GND (B18:GND) [Inner Shield], 11:FLG (B19:PFLG*) [2], 5:COVER ON (B20:PSTS*) [4], 8:BUFR RDY (B22:STI0*) [5], 7:READY (B23:STI1*) [7], 34:GND (B24:GND) [901]

Also, at the 98032A Interface Connector, pin A25 (Chassis) is connected to the Cable Shield. And the 98032A Configuration Board must have wire jumpers installed at positions 4 and 5. (This configuration board wiring and cable make a 98032A into "Option X71".)

The wire color codes are the same as resistor color codes: 0:black, 1:brown, 2:red, 3:orange, 4:yellow, 5:green, 6:blue, 7:violet, 8:gray, 9:white. When there is more than one color listed for a wire, the first color is the insulation color, the second is the wider stripe, the third is another, narrower stripe.


Many thanks to you,Ellis,for your kind message!
It is very helpful to me.I will investigate thoroughly
once more the pluggable interface PCB to compare it with
your kind info.What type of calcs are you interesting of?
If I can be useful to you,please,ask me.I am very grateful
to you for your kind service and I feel obliged myself
towards you.
I'm still hunting the circuit diagram of the printer
in question for making known to me the type of the voltage
regulators'transistors to be changed into the good ones.
If somebody of your friends would have it(the drawing)
or have already repaired that printer,I am grateful
in advance for any info message on this matter.
The best regards and the best greetings from the
Polish Coast to you ,Ellis and to you all,Friends!

Jack T.L.


You're welcome, Jack. I'm interested in all calculators! and many other areas, especially test and measurement equipment.

I don't have a 9871A printer and there is no documentation for it in the Museum CD-ROM set. However, if you can find any HP part numbers on the devices you are wondering about, we might be able to find out what standard component types they are. If they are on the bottom of the unit the markings might have rubbed off, but hopefully there is some marking left.

HP used a fairly regular component part number system, with four digit prefixes for families of components and four digit suffixes. Sometimes they truncated the prefix if space was limited on the device package. Here are some examples of prefixes I found in my service manuals:

1818-xxxx memory IC's
1820-xxxx digital IC's other than memories
1826-xxxx analog IC's

1850-xxxx PNP germanium transistors
1851-xxxx NPN germanium transistors
1853-xxxx PNP silicon transistors
1854-xxxx NPN silicon transistors
1855-xxxx FET
1884-xxxx SCR (HP used them for power supply crowbars)

However, I found 1820-0477 for an LM301AN op amp, and 1820-0493 for a LM307N op amp (and 1820-0430 for an LM309K +5V regulator) - maybe these were early IC part number assignments made before they developed the system of IC family part number prefixes.

HP also used alpha-numeric prefixes for IC's that they made, such as 1LB3-0003 for the HPIL chip.

I know your printer has TO-3 parts, but I found the following part numbers for TO-220 three-terminal regulators in a digital voltmeter:

1826-0122 7805
1826-0396 7815
1826-0214 7915
1826-0527 LM337T

This just illustrates that parts of this type have the same part number prefix (1826) and that the part number suffix bears no relationship to the standard part number - HP probably just assigned part numbers sequentially as they were used in designs.

I looked for TO-3 devices in my service manuals. Here are the parts I found:

1820-0430 LM309K (+5V regulator - note 1820 prefix)
1850-0021 Delco 2N441 (I think this is a TO-3)
1850-0098 "PNP germanium 300 kHz 250 mA"
1853-0059 Motorola 2N3791
1853-0063 "PNP silicon selected"
1853-0305 Motorola 2N5875
1854-0063 2N3055 (under "Mfr. Part Number", says 1854-0064 - might be HP selected)
1854-0225 "power NPN silicon" (in Harrison power supplies)
1854-0589 Motorola MJ3772

That's all I can find so far! Lots of TO-220's, but not too many TO-3's. All of the transistors were used as series pass elements in voltage regulators. There is a partial HP part number cross reference available - we might have to look in the Archives for it. Let me know if you can read any of the numbers on your devices.


I found a few more TO-3 devices in HP service manuals:

1826-0123 "-12V regulator"
1826-0631 "IC:regulator"
1853-0310 2N4398 (PNP silicon)

Based on pin assignments, I think 1826-0123 is an LM320K-12 or an LM7912CK. Judging by a photograph showing a manufacturer's part number, the pin assignments in the schematic, and the resistor values which were used to set the output voltages, I think 1826-0631 must be an LM350K, an adjustable (1.2-33V) three terminal positive regulator with up to 3A output current.

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