HP 9114 disk drive battery charging



#10

Oddly enough, the 6V lead-acid batteries these things use are still widely available.

The charger, now...

I got this at least a decade ago and while I'm pretty sure I had a charger at one point, I don't seem to now. I say "Don't seem to" because although the charger receptacle on the battery box takes the same plug as do the desktop and handheld computer HPs (such as the HP-97), I kinda doubt that charger would work well. For one thing, the battery box notes:

"20V / 500MA MAX INPUT"

20V to charge a 6V battery seems high to me, but in any case it's way more than any of the chargers I have put out. Perhaps it's because the charger would be expected to run the disk drive (old-style Sony 3.5" drive and a large controller board) while the battery is charging.

I guess I could simply put the battery on a car battery charger set to 6V. That should work.


#11

Hi David,

The 9114 uses the same charger as the HP41, the HP41 printer, the 41 IL printer, the 71/75, etc. Specifically the 82059 (US) charger with an output of 8VAC and 3VA. The charger will NOT run the unit with a dead battery. The battery needs to be able to maintain a charge for the disk drive to operate.

Hope this helps.


#12

That does help, thanks. I have several of those chargers.

#13

I charged the battery all night, and while I can read just over 6 volts off the battery terminals, there's 0 volts at the plug that connects to its mate inside the drive's battery bay.

There's a small circuit board in the battery box containing a 4-pin device that I assume is some sort of rectifier, a single transistor, and three discrete components (a resistor and probably some diodes.)

A three-pin and a two-pin cable plug into a 5-pin connector on the board. You can plug them in in either of two arrangements (2 pin first or 3 pin first), but neither produces any voltage at the output plug.

I assume there's a problem on the little circuit board. Is this worth trying to fix (and if so, any suggestions other than replacing every component)? It seems many of these old drives just wire the battery in directly to the drive and charge the battery externally.


#14

Hi David,

Ok, lets see what I can make of this. First off let me tell you that I am a programmer NOT an electronics person so there are much more qualified people on this site. But here we go...

1. I am looking at the battery carrier for a 9114A My B units are packed at the moment.
2. That 5 pin connector that you refer to. On my unit there is a 3 pin orange plug that connects to the side farther from the connector that mates inside the bay and a white 2 pin plug that plugs in closer to the bay connector. The white plug has 2 grey wires running to the charger socket while the orange connector has red black and white wires running to the battery and the internal (bay) connector.
3. I guess if I were to tackle it I would try to see how far I could trace the power (at the moment my voltmeter is also packed). And see if you can identify what component is failing.

Sorry, I realize that this is not much help other than telling you which plugs go into which part of the socket on the board assuming that yours is the same (my board is labeled Rev A). Hopefully one of those electronic types will chime in with more info.

Good luck.


#15

Yeah, I'm a programmer, too. I can solder but that's about it. I think I remember the resistor color code.

I see 6V from the battery up to the rightmost pin on the transistor. On the other two contacts the reading is 0.03V, so the power isn't making it through that component.


#16

I think I see the problem: the lowest component on the PCB, right under the resistor, is a green resistor-sized object labeled "3A". It's obviously been replaced at some point judging by the solder marks. The 6V goes through this component to the output, and none of this is making it through.

I suspect this is a blown 3A fuse. I also suspect it's too small: 6V@3A is only 18 watts, and I think the 9114 probably requires more than that.

The transistor and rectifier are only used for charging, as far as I can tell. Mind you, I don't know much about electronic hardware.

So I plan to replace this fuse with a 5A fuse in the next day or so unless someone thinks it would be a really bad idea.

#17

One of those things that looks like a resistor is probably a micro-fuse, your description of the electronics in the battery pack would seem to match the 88014A battery pack and according to Mr. Duell's schematic the fuse is in between the + side of the battery and the W/R (white/red?) wire that goes to the connector between the battery pack and the 9114. The schematic can be found at
http://www.hpmuseum.net/document.php?hwfile=2718

Edited: 24 May 2011, 5:55 p.m.


#18

Yep, that was it. The micro fuse was blown and fortunately replacing it was within my limited soldering skills. Everything works great now!


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