HP 3421 DC power option


I have a HP 3421 Data Acquision Unit with the DC power option (212). This option adds a connector to run the unit off of 12VDC power. It also has an outlet and three cables with HP 82059 type ends to power a HP calculator, disk drive and ThinJet printer. The manual for it is very specific that ONLY the HP 71B, 9114 and HP 2225 ThnkJet are to be powered from these connections. Does anyone know why? Or do you know for certain if other devices like the HP 41, cassette drive, etc can be safely operated from them? FWIW, the cable marked "controller only" puts out 10VDC and the other two put out 8.5VDC.



The service manual for the 12VDC option (3421-90009) (page 1-2) says:

1.6 The 12V battery option allows the 3421 Data Aquisition and Control Unit, an HP-41C/CV or HP-75C Handheld Computer, an 82161A HP-IL Digital Cassette Drive and an 82162A HP-IL Thermal Printer to be operated from an external 12V sourcem such as a standard 12V automobile battery. ...

1-7 A cable assembly has been supplied with this option that will, when plugged into the rear panel of the 3421A, provide power supply output ports for the computer (HP-41C/CV or HP-75C only), cassette drive (82161A only), and printer (82162A only). This assumes, of course, that the battery option is connected to an external 12V source. These power supply ports are not active when the 3421A is connected to the AC line only.

!!! I'm not sure, that it would be good connecting the battery AND the mains at the same time !!!

The service manual for the 12VDC option (3421-90009)(page 8-1) says:

8-7. This option is designed to operate from an external power source having a having a voltage of between 11Vdc and 15.3Vdc. The external source voltage is used to generate the HP-41C/CV or HP-75 power supply voltage (9.5Vdc-10.5Vdc), plus the printer and cassette drive power system voltages (8.15Vdc-8.7Vdc). ...

I can see, that the controller voltages are generated by a transistor (2N4037) and regulated by an operational amplifier. The other voltages are generated by an 7885C regulator (8.5V)

The 3421A Data Acquisition/Control Unit 3056DL Data Logger Technical Data, November 1985 (5953-6975)

says on page 19:

Option 214 battery connection (Note the option 214!!!)

- blah blah 12 Vdc source blah blah - Extend battery lifetime of the HP3421A and other system devices such as the HP71B, HP2225B, and HP9114


That's what I know. I have the HP-IB interface on mine and so I can't use the battery option and I don't have one. Sorry, no experience.

I'd not see any problem connecting other peripherals, though I would keep the controller connected to the "controller" plug just because of more voltage. Might be, that they didn't want to overheat the power circuitry of the peripherals, but maintain a healthy supply to the controller. I don't have a clue.

BTW: Do you have or do you know anybody who owns a 82479A Data acquisition pac ROM ?



Thanks for the information. I have a service manual too but mine is PN 03421-90012 dated Feb 1986. My manual doesn't mention the HP 41, cassette drive or 162 printer!

I have option 212 in this 3421. The manual covers the option 214 but it does have a manual change page that shows option 212. The main difference seems to be that the two outputs are 10.5 VDC instead of 8.5 VDC. The 8.5 VDC is controlled by a 7885C regulator in the 212 but the 10.5 VDC is controlled by a series pass transistor with op amps in the option 214. The 212 uses board PN 03421-66503 and the 214 uses board PN 03421-66515. I'm not sure if the "controller" output is the same in both options but I think it is. The 212 information that I have doesn't show that output but I think the only change was in the other two outputs.

BTW you can run the 3421 from the mains, internal battery and external 12 VDC power simultanously. It will automaticly switch between them with no problems. I tried it yesterday. Both the 12VDC and the mains power will charge the internal battery even when the 3421 is turned off.

You are correct, the DC outlets only have power when you are operating from the external DC power.

If you want the complete specifications for the option 214 let me know and I'll send them to you.

I have HP-IB options in the other 3421s, one of these days I'll hook them up to a HP 85 and try them. No, I don't have the HP 71 data logger pak, I've never seen one. Do you have the data logger program for the HP 85?



I took the notes from the _battery_option_ service manual, not from the 3421 service manual.

I could scan the pages, if you like.

>If you want the complete specifications for the option 214 let me know and I'll send them to you.

That could be interesting

>Do you have the data logger program for the HP 85?

No, I don't even have a 85 (yet). I'd be interested in the pack anyway ...

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