A ? about a few flakey Woodstocks ...


i've got a couple of Woodstocks -- an hp-22, an hp-25 and one other -- that all have the same problem. When hooked up properly -- ie with a battery pack installed and a charger plugged in -- all I get on the screen is an 8 all the way on the right of the screen. The keys have no effect; the 8 remains. Any idea what's going on here? Anything I can do about it? Thanks!


Erik, this seems to be a problem covered here earlier several times. Be VERY sure you have good accumulators in the battery pack and they make good contact with the calculator PCB, before you connect the calculator with the mains. Else you may damage (even destroy) your calcs easily. You mentioned in another thread you have suboptimal battery packs, so TAKE CARE !!


Good battery packs are indeed essential to many elder HP's. I would indeed be very careful with connecting them to the ac-line without inspection of the pack and the contacts related to it. I have no experience with the typical woodstok models but the 67 is based on the same technology and its manual says explicitely that a battery-pack must be installed when running the calculator on the ac adapter. The spice series (30's with LED) require even a battery pack in good condition to run on the ac line. If a spice's pack is not OK the display blimps constantly without any response to the keys.


uh oh!

but riddle me this. i'm using the same battery pack and charger to test all my woodstocks. so far about five of them have tested just fine, though of those one or two need some time to warm up, as it were; iow, the charger has to be connected to the calc for a while before it works the way it should.
and then there are those three that only respond with an 8.
given that some calcs are working fine with the battery, does it still suggest to you that it could be a flakey battery pack problem and not a flakey woodstock problem?
is there a way for me to test my battery pack to see if it's okay to use? if not, i suppose i could tear one apart. if you know it off the top of your head, what radio shack battery replacement would do? if you don't, i'll try to find it online.


from my interpretation of the MoHPC battery page, it would seem that a couple of radio shack 23-191 batteriess might work; they are 1.25V/600mAH Ni-Cd Batteries with Tabs, though i'd need em without tabs. what do you think?

update: well, er, uh -- i did a search and saw an earlier thread where the consensus was that a couple of regular AAs would also work, as long as you got the polarity right and didn't use the charger. So, I opened a battery pack, put a couple of AAs in, put em in one of my flakey HP-25s, turned it on, and up came everything right as rain. for a split second. then the LEDs starting acting all screwy. so i turned the calculator off. took out the battery pack, looked at it dumbly, reinsterted it, turned the poor 25 back on and ... nada, nothing, black screen.
maybe i should have gone with the 1.25 nicads instead of the relatively overpowered regular AAs.

Edited: 31 Dec 2005, 11:53 a.m.


Using the charger and having no connection at or between the batteries due to dirt or invisible gunk is the same as no batteries to a woodstock or spice model. You don't get points for meaning well either. It is playing Russian roulette with your calc; you will kill it sooner or later. Due to what people here have posted and one sad personal experience; I have stopped using chargers on those models. I charge NIMH cells outside the calculator or use disposables. I have never heard of a fully charged alkaline damaging the ACT chip but i burn slightly used ones anyway.

It's nice to have the AC adapter as part of the full set, it's just a dangerous practice to use it.


thanks all for the sage advice. it was the battery pack after all. i went to radio shack, got some nicad AAs and a charger, charged the batteries up -- bingo bango, woodstocks that were once dead or near so sprung miraculously back to life, no harm done that i can see. bueno. again thanks ...

and i'm sure i'll have more questions like these as i make my way through my collection. please, if you would, bear with me ...


Hi Eric,

then the LEDs starting acting all screwy. so i turned the calculator off. took out the battery pack, looked at it dumbly, reinsterted it, turned the poor 25 back on and ... nada, nothing, black screen.

I get this from time to time with my 29c, which has a rebuilt battery pack. If I slide the battery pack as if to take it out, but stop short, it restores normal operation. It seems to be a battery contact issue. I have not welded a strap across the end of the batteries in my rebuilt battery pack, relying instead on the spring to maitain the contact between the two cells. I'm sure this has a direct bearing on my occasional lack of continuity problem.
I'm in complete agreement with the other posters when they advise not to hook the charger to the calc, but rather charge the batteries externally. That very nifty external battery pack charger that HP made for the woodstocks would be the perfect thing to use (I have one but haven't seen seen it since my last move.)
Best regards, Hal


i went out and bought a radio shack charger yesterday but today, while pawing through my woodstocks, i came upon one of those HP chargers. Very nifty. Only wish I'd known about it yesterday. ah well!


The problem is most likely a bad ACT chip. This usually shows up as all 00000000 display, but sometimes you get the (very bright) 8.

It may also be a problem with residual corrosion on the circuit board. I would try standing the board up to the top of the battery contacts in an ultrasonic cleaner with vinegar in it. Run it for a couple of cycles, then repeat with three cycles of fresh clean water. Shake off the excess water and let them dry overnight.


Is it possible to easily replace this ACT chip?
Can we find it in a radio shack shop ?


The only source is another HP calculator. All the Woodstock series ACT chips are compatible except the HP27 chip is unique.

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