HP-41 Related Repair Questions



#2

Hi All,
I purchased an old HP-41C off of e-bay - and, basically, the condition of the unit was much worse than I was lead to believe. I guess I should have insisted on seeing a picture of the battery contacts - all 4 are quite corroded. I'm not sure, this HP-41C looks like it might be the "tall key" model. It has a serial number of 2037A00417. It has a battery pack that looks to be in not very good condition and no charger was included. All the keys have a good click except for the "1" key - it seems to not return to the correct position unless you manually, gently, pull it back. I also picked up an HP 82143A printer. Initially nothing happened when I plugged it in and I thought it was dead. But after 4 or 5 minutes now both the "Bat" and the "on" light are lit - so perhaps this unit will actually work. The battery has a "New" sticker on it - but that seems to convey little information since there is no date! ;-)

Does anyone know if the batter pack from an HP-41CV (that uses 4 N alkaline batteries) will work if plugged into the HP-41C (that originally came with a recarhgeable battery pack)? Any chance that the charger that came with the HP82143A printer will work with this HP-41C?

I am thinking about trying to find 4 small pieces of copper - and trying to solder them onto the existing contacts. Anyone know where I could find some copper that is very thin/flexible? I have never soldered anything in my life - I have a soldering iron - still in the shrinkwrap - someone gave me last Christmas. Anyone care to lay odds of success? ;-)

Thanks for any hints, tips or pointers to additional info.

Kevin


#3

I'd say your prospects of repair are slim given your self described skills (at least keep the soldering iron away from this). However, there is available trace paint (not sure what the real name is) that you could paint/paste onto the poor contacts. Also consider cleaning the unit ie a nice NEW soft rubber eraser (not the gritty type) if you are adept at small dissassembly, that might remove oxidation from the chip pad contacts enough for the unit to power up (same rubber eraser can be used to touch up contacts if they aren't too bad, but you may also rip them up, especially if you don't know what you are doing).

Before you go further, you might look over a few repair tips posted here and elsewhere.

Your keyboard issue doesn't sound good, but otherwise you can probably get your calc running if you proceed cautiously and with care.

There are a couple of repair places out there for these older calculators, you might contact them as well.
One is fixthatcalc, but I understand they have a bit of a backlog of work.

#4

Hello Kevin:

Yes, you can use the HP41CV battery pack with the HP41C.
Yes, this charger works fine with this battery pack.

To repair your calculator, if you want to do it yourself, you can visit www.clonix41.org. This is the Diego Diaz web. He sell the flexible piece you must change to repair the battery contacts.

Good luck.

Iñigo


#5

Wow - that is very cool. I dropped him a note to see how much it would cost.

Thanks,

Kevin

#6

It is common on tall key 41's for the 1, 2 and sometimes the 3 keys to be flat - that is to say they lack the normal tactile feedback. It shouldn't stay down though when pressed. That is usually caused by something sticky having been spilled onto the keys.

Battery contact damage that doesn't extend to the port contacts can be easily repaired with 1/8" brass U-channel available in hobby stores. Remove the block from the calculator, cut 4 small lengths (~0.15",3.5mm) of the channel and solder over the damaged ends, you might have to scrape the film off the copper on the port connection side if the damage is severe. I have repaired many a connector that had no foil left over the contact area, I had to cut it all away due to corrosion. The brass channels were epoxied into place and soldered to the remaining foil that had been scraped clean.

Here's a good condition repaired block:


Edited: 30 Oct 2006, 10:37 p.m.

#7

Hello!

Quote:
1. Does anyone know if the batter pack from an HP-41CV (that uses 4 N alkaline batteries) will work if plugged into the HP-41C (that originally came with a recarhgeable battery pack)?

2. Anyone know where I could find some copper that is very thin/flexible?


1. Yes it will!

2. One of my HP-41s has been repaired (by one of its previous owners) with pieces of copper shielding from a co-axial cable (probably a TV-antenna cable).

Soldering these awful horrible flexible pcbs is very tricky. If you want to be sure that you dont further damage your calculaor, it would be better to glue the copper in place and connect it with conductive silver paint.

Greetings, Max


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