HP82161A Battery Voltage



#2

I have a HP82161A cassette drive which has no battery pack (I assume it died some long time ago). The unit is now powered by 4xD cells (~6v) but the battery warning is displayed intermittently during operation.

Is this because of the higher internal resistance of these cells (as opposed to nicads) or is the original nicad pack a higher voltage?

I'd like an indication of the nominal output voltage of the nicad pack before I increace the voltage to approx 7.5 volts by the addition of another cell.


#3

Got it in one Steve, higher internal resistance, however you might like consider thicker cables = lower voltage drop? *I* would not increase the voltage to the drive, I'd seek a lower internal resistance power source and possibly a large reserviour capacitor (10,000MFD?). Possibly some Ni-Cads?


#4

Yeah, internal resistance all right. :-(

The batteries are not too fresh, having a combined output of 6.05 volts under no load (I would expect 6.4 to 6.8 for new cells (1.6 to 1.7v per cell))

Under load the analogue multimeter shows a drop to around 4 volts from time to time as the cassette motor does it's thing.

Maybe I'll try to find some nicads or maybe NiMH batteries that I can put together in a pack and squeeze into the battery compartment.

But the originals (nicads I assume) were 4 cells (4.8v) or 5 cells (6v)????


#5

The original battery pack for the HP-IL Cassette Drive, Printer, and HP-82143 HP-41 printer were 4 Sub-C size Ni-Cd cells, producing a nominal voltage of 4.8 volts under load. 4 D cells should easily provide this voltage under load assuming that they are alkaline and not depleted, and the connections are of low resistance. In fact, four alkaline C cells should suffice to power these instruments.


#6

The cassette drive was said to be a real NiCad Killer because of the high peak currents drawn by the two motors. I'd recommend using some special Nicads for this drive, like them used in model cars.

I used the Panasonic Red-Amp for this purpose some years ago and my rebuilt pack works until now. I must admit that there was not a lot of use, because I own a disk station (another battery problem).

I don't know about the internal resistance of NiMh accus (will have to look, if somebody is interested) but I think that the higher capacity is a real advantage.


#7

Hmmmm, maybe I should power it from a 6V sealed lead-acid battery (the little gel cells, not a motorcycle battery :-)


#8

Yup the little 6V lead acid cells would be ideal, *please* put a fuse in it would be easy to start a fire with these. On the negative side you have to use a constant voltage charger...


#9

I think, it's ok to use good NiCads or NiMhs. Remember that the cassetted drive is meant to be a PORTABLE device, so additional chargers, ... are not recommended

I also think the battery door should be closed during operation, so leave it in near original condition.


#10

Unfortunatly (in that respect) mine has already had a new connector placed in the side of the case where the batteries plug in.

I'd sort of like to make them internal, and I think 4xAA nicads (1000 mAH) would do the trick.

But:

1) how do you open the case?

2) is the charger for this unit the same as that for the HP41 nicad pack?


#11

Can't answer how to open the 82161 case, but the charger is the same as for the HP-41 Ni-Cd pack.

#12

On the subject of batteries...either use high capacity (900mAH+) AA cells or find some sub-C's. I somehow doubt that the common-or-garden (600 mAH) variety will prevent the voltage dip you suffer. As to case opening, HP normally hide these under lables

#13

It's rather easy to open the cassette drive.

Remove the rubber feet and remove the srcrews under them with a phillips screwdriver (I think). There is an additional hole with a screw in the middle of the machine.

Why do you want to open the case? I'm sure you will want to open the battery door. You can slide the two small pieces between the left rubber feet (cassette drive seen from the front side upright) to the middle. This opens the battery door. You will then see two contacts.

I'll have to check out which is the positive and which is the negative. DO NOT EXPERIMENT with that. Applying reverse voltage might destroy the drive.

I'll check that and post it here


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