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HP Forum Archive 04

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Using AC Adapter/Charger with 67 or 97
Message #1 Posted by Mike Davis on 4 Oct 2000, 2:56 p.m.

Does a battery have to be installed to use the 67 and/or 97 on the AC Adapter? Someone told me that they could not test a calculator because they only had an adapter and did not have the battery.

How useable are either of these models with only an AC Adapter and no battery?

      
Re: Using AC Adapter/Charger with 67 or 97
Message #2 Posted by Rupert (European Union) on 4 Oct 2000, 3:35 p.m.,
in response to message #1 by Mike Davis

> Does a battery have to be installed to use the 67 and/or > 97 on the AC Adapter? Someone > told me that they could not test a calculator because they > only had an adapter and did not > have the battery. > > How useable are either of these models with only an AC > Adapter and no battery?

Here is a post from comp.sys.hp48:

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From: John H Meyers <jhmeyers@miu.edu> Newsgroups: comp.sys.hp48 Subject: Care of old HP calcs and chargers Date: Thu, 21 Sep 2000 07:30:21 GMT Organization: Deja.com - Before you buy. Lines: 56 Message-ID: <8qcddl$uuj$1@nnrp1.deja.com> NNTP-Posting-Host: 208.145.207.60 X-Article-Creation-Date: Thu Sep 21 07:30:21 2000 GMT X-Http-User-Agent: Mozilla/4.73 [en] (WinNT; U) X-Http-Proxy: 1.0 x57.deja.com:80 (Squid/1.1.22) for client 208.145.205.253, 208.145.207.60 X-MyDeja-Info: XMYDJUIDjhmeyers

I'm prompted to post this by seeing old HP calcs offered for sale with notices such as this:

"HP25C: Includes charger and battery pack, which looks fairly clean. Compartment is clean. When I plugged it in, I got a flashing display, then nothing."

Plugging that calc in without a good battery pack in place would probably have destroyed it, unfortunately.

Practically all HP "LED" calculators whose charger has only two pins depend upon a fully functional battery pack to absorb and filter the output of the charger, which has no internal filter or voltage regulator itself (it is often just a transformer, no power supply electronics in it at all).

Without the battery pack, the transformer delivers too much voltage to the calculator; I destroyed one or two myself before I learned better.

Three-pin chargers (HP35, HP80, etc.) are okay (they deliver a filtered steady voltage supply for the calc, plus another separate charging voltage to the batteries only), but two-pin chargers are life-threatening to old HP calcs without fresh, chargeable batteries securely in place.

Radio Shack (USA) may still be selling "Replace-a-cell" NiCd AA-size batteries; these have the "flat tops" exactly like the original HP-supplied cells ("button-top" cells are slightly longer, and will flatten and damage battery contacts if inserted into some calc models); cells removed from cordless phone battery packs (often on sale at Wal-Mart etc.) are usually similarly without the "button tops" and if so will also work fine.

In a pinch, you can, believe it or not, bang down the "button-top" of a couple of AA-size alkaline cells with a hammer, to make cells which will fit and properly operate an HP calc (but you should not then use the charger at all, because it would overcharge and possibly cause ordinary batteries to burst).

Knowing these facts will help to preserve and increase the value of any old HP calcs still circulating in the market, and I hope that any sellers who read this will profit by this information (and "save the skeets," as Tom and Ray say :)

----------------------------------------------------------- With best wishes from: John H Meyers <jhmeyers@mum.edu>

Sent via Deja.com http://www.deja.com/ Before you buy.

************************************************************

The HP-67 is not mentioned above but its charger has three pins too. I tested my HP-67 purchased from eBay some months ago, without the accu-pack, at my own risk. It seems to work.

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Re: Using AC Adapter/Charger with 67 or 97
Message #3 Posted by Viktor Toth on 4 Oct 2000, 9:19 p.m.,
in response to message #1 by Mike Davis

HP-67: the calculator works with no battery pack installed, receiving regulated voltage from the charger, but there's not enough current to drive the card reader.

HP-97: the calculator does NOT work with no battery pack installed, but according to HP docs, it is not damaged either in this configuration. (This is in contrast with Woodstocks, especially 'C' Woodstocks, that can die a quick and ugly death this way.)

Viktor

            
Re: Using AC Adapter/Charger with 67 or 97
Message #4 Posted by DaveJ on 5 Oct 2000, 10:04 a.m.,
in response to message #3 by Viktor Toth

The HP-97, 91, 92 printers will instantly be destroyed if printing is attempted without a battery pack installed (or some other means to achieve proper electrical conditions) The card readers may not suffer as catostrophic damage but it will not be good for their operation.

                  
Re: Using AC Adapter/Charger with 67 or 97
Message #5 Posted by Viktor Toth on 5 Oct 2000, 6:53 p.m.,
in response to message #4 by DaveJ

Hmmm, what is the nature of the damage to the printer? I'm asking because I don't think I ever tried doing this (nor do I plan to, for all the obvious reasons); in fact, I recall only one time when I ignorantly attempted to operate an HP-97 without a battery pack many years ago, but I learned quickly that it isn't a good idea.

The HP-97 service manual, however, does state on page 2-5, that "with batteries removed, the calculator will not be damaged by connecting the ac adapter/recharger to the input terminals; however, it will not operate correctly until the batteries have been reinstalled."

Viktor

                        
Re: Using AC Adapter/Charger with 67 or 97
Message #6 Posted by DaveJ on 6 Oct 2000, 10:19 a.m.,
in response to message #5 by Viktor Toth

The nature of the damage is the printer motor gets too much juice and the gears on the drive mechanism (nylon) get stripped and are virtually irreplacable outside scavanging from another HP calc.

This only occurs if you attempt to print while no battery is present and I suppose it may not occur every time but I would hate to do a statistical study....

                              
Re: Using AC Adapter/Charger with 67 or 97
Message #7 Posted by Viktor Toth on 6 Oct 2000, 11:56 a.m.,
in response to message #6 by DaveJ

Gotcha, so the problem is not electronic in nature. This may also explain the relatively frequent reports I heard about broken nylon gears in Topcats.

Viktor

                                    
Re: Using AC Adapter/Charger with 67 or 97
Message #8 Posted by Katie wasserman on 7 Oct 2000, 12:01 a.m.,
in response to message #7 by Viktor Toth

The yellowish gear may indeed have its teeth stripped by running it on the AC power supply only. However, the gear itself does decay over time. I've got a few 97's and they all have spur gears that are very brittle and starting to fall apart. So I think that it's both a nylon decay problem and a motor force problem. I'm very actively looking for a source of replacement gears. If anyone can help, I believe the specs are as follows:

24 pitch - 32 teeth total (about 3/8" diameter) - 3/32" face

3/32" bore

1/4" hub diameter - 3/32" hub projection

A spur gear with the above specs made from Delrin would be ideal.

                                          
Re: Using AC Adapter/Charger with 67 or 97
Message #9 Posted by Glynn on 7 Oct 2000, 3:16 a.m.,
in response to message #8 by Katie wasserman

Just checking Katie; Would that outer diameter be 1-3/8"?

                                                
Re: Using AC Adapter/Charger with 67 or 97
Message #10 Posted by Katie Wasserman on 7 Oct 2000, 12:41 p.m.,
in response to message #9 by Glynn

Glynn,

Nope. 3/8" is approximately correct. 32 teeth at 24 pitch is all you really need to know to determine the diamter of the gear.


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