HP-94 question


Is the 3 prong plug for the charger on this unit HP proprietary?

Edited: 29 Mar 2013, 6:59 p.m.


It's probably proprietary to Canon.


Thanks, I think I found one on eBay. 3 prong "Mickey Mouse"


The power connector on the HP-94 is not proprietary I think but it is rare.

I'm not sure which one you found on ebay, but the "mickey mouse" ones I see are for 120V AC and not even close to the size used on the HP-94. Of course the HP-94 needs low voltage DC to charge its battery pack.

I was able to make a charger using the cable from on old Hayes modem (don't recall the model but I think it was a 2400) power supply -- this is an exact fit -- and a 10VDC power cube. If you don't have the right connector the easiest way is to unscrew the battery pack and use some thin screws or nails to plug into the battery pack connector. It's crud and sort of a pain but you don't need to charge these too often.


Can you confirm the + Connection on the battery pack is near the edge?

Have you opened the pack to re-cell? Any suggested methods to open?


Yes it's near the top. (You must not actuality have a 94 in your possession, it would be extremely obvious).

Replacing the cells in the battery pack is about as difficult as it gets. The pack is welded shut and you need to cut it open, there's just no other way. I use a Dremel tool with the tiny saw blade for this. Luckily the rubber grip that surrounds the pack will be able to hid all the ugliness of the cutting and re-gluing.

The pack uses 4 2/3-subC nicad cells. These are both difficult to find and difficult to insert in the cut open pack. I recommend using 4 AA nicad tabbed cells instead. If you are not likely to use the HP-94 much, the off-state current draw is near zero and the nicad self-discharge will be the dominate current drain. So, you could (and I did) use 4 AAA primary cells in holders inside the battery pack. If you use Energizer lithium cells, they will likely last many years.

There is little you can do with the 94 without writing a program for it. See this thread for more details.


No I actually do have a 94. Just want to be double sure before applying power. There was a wee bit o voltage in the cells.

I'll jumper a 4 cell C tray I have to the unit to see if it works.


I turned on today. The LCD has a vertical column of pixels lit up about 3/4 from left side.

Is this normal or is there a defect?

Normal Error 210, Error 212 codes then the copyright info.

This unit came out of the Calculator Division. It was a dumpster salvage unit.

Edited: 30 Mar 2013, 7:32 p.m.


is this normal or is there a defect?

It's a defect, unfortunately.

Normal Error 210, Error 212 codes then the copyright info.

210 is a low voltage on the backup battery error. There's a lithium coin cell in the memory compartment that needs to be replaced. Remove the back cover and you'll see the coin cell holder. This happens often if the main battery pack runs out. The current needed to hold memory using the backup battery seems excessive to me.

212 is a main memory directory table checksum error. This is almost certainly due to the dead backup battery. After you replace the backup battery you need to initialize main memory using the 'I' command.


"not proprietary"

true. i've seen that plug a couple of other places. one, i think, was german.

there's also a very similar one that IIRC would need to be filed on one corner to fit, but it could be used.


Also some of the Sanyo ICC series calculators use it as does a Sharp, a Friden and a Brother unit that I have. Still I consider it rare in that I've never seen it available as a connector for purchase in any electronic catalog or on a website. Perhaps I'm not looking hard enough.

there's also a very similar one that IIRC would need to be filed on one corner to fit, but it could be used.

This was also the situation with the power plugs on the Hayes 1200 and Hayes 2400 modems as I recall. They differed from each other because one had an extra corner.

Edited: 31 Mar 2013, 12:34 a.m.

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