I've also transferred these as a couple of big files to a PC, thanks to the ST program from dbit.com & using the TK50 drive on a TZK50 SCSI-TK50 >adaptor. Now, how do I use these on the SimH PDP11 emulator! ?

It wasn't me, even though I have a fair collection of HP calculators (including, I think, all but one of the devices to use that PSU). However, this seems like a good place to post some information on repairing said PSUs. This unit is one of the few that charges the battery properly. The PSU has 3 connections to the calculator. Ground, a constant-voltage (4.2V) supply to run the logic and a constant current (55mA) supply to charge the NiCd. When the charger is not connected, then the battery is connected to the logic supply line. When you plug the charger in, it moves a contact in the calculator plug away from the pins and disconnects the battery and the calculator. For models _without card readers_ (35, 45, 55, 70, 80) it's safe to connect the charger without a battery pack in the calculator. There is no connection between the battery and anything else when the charger is plugged in.

good battery pack installed in the calculator before connecting the charger. Otherwise the card reader sense amplifier chip sees the full voltage of the constant current supply (about 16V) and may fail. This chip is, of course, HP custom.

Anyway, getting back to the charger. There are basically 3 stages to the circuitry. An unregulated DC PSU giving about 16V (transformer, 4 diodes as a bridge rectifier, 400uF capactitor). A constant voltage regulator (resistor + zenner and an emitter follower). And a constant current regulator (a couple of transistors and resistors). All discrete components, nothing custom. As to what goes wrong with them : 1) Open-circuits in the output cable, particularly close to the calculator connector. Trivial in theory, harder in practice. You have to slice open the connector as it's moulded to the cable.

2) The 400uF smoothing capacitor goes open-circuit.

3) Some versions have a fuse between the transformer secondary and the rectifier. It's a soldered-in picofuse. Sometimes it fails for no good reason. 4) The power transistors (especially the NPN one in the constant-voltage circuit) can go open-circuit. Here's an ASCII-art schematic of the classic charger.... HP82011 (etc) 'classic series' charger -------------------------------------- (Unregulated PSU) -----)|| )||(----+----->|--+-----+------ +16V )||( | | | )||( | +-->|--+ === 400uF Mains)||( | | --- )||( +--)--|<--+ | )||( | | | )||(-------+--|<--+-----+---+ -----)|| | --- /// (Constant voltage regulator) c e +16V ----+------\ >---------------------- +4.2V Logic Supply | \ / (NPN power transistor) | ------- / | b \ | / 470R | \ | | | +---------+ | ---, ^ 4.7V zener | --- /// (Constant current charger) (PNP power transistor) 13R e c +16V -----+----\/\/\---+--------> /------------- 55mA constant current | | b \ / charger supply | ----- ----- | e / \ c | b +----------> \--------+ (PNP signal transistor) | / \ 4k7 / \ | --- /// -tony