HP29C Problem

[sgansky]

Turning unit on I get:

0 0 0

Nothing seems to work. This is on a AA battery pac

Thanks

Steve

[burkhard]

Nobody has chimed in yet, so I will give my 2¢ amateur reply.

It looks like you are a new member here, so welcome.

All these "Woodstock series" HP calculators from the 1970s (including your 29C) have what I consider a horrendous design flaw. If you try to power them with the AC charger and no battery (or a battery that has internally failed "open" or even if there is some corrision/crud on the contacts), the calculator is nearly INSTANTLY damaged. Poof! The charging circuit relies on the battery being present in order to protect the calculator itself.
Needless to say, after 40+ years all the old batteries either missing or bad and some of those bad ones might have failed open. As a result, the majority of these calculators sold on auction sites, garage sales, wherever by non-specialists have been damaged. When the kids are cleaning out Grandpa's house after he passes away, they don't know the rules and just start plugging things in to "see what works"...

The good news is that 29C is a pretty desirable model and so is worth fixing. A gentleman in Germany sells several kits to repair them either to original specs or to a souped up version. The website is http://www.panamatik.de/html/hp_calculat...r_kit.html

You can search this forum for "ACT" and you will find lots of posts on the problem. Terrible design choice on HP's part, but I guess back then people treated a calculator as a major purchase and really studied the manual and paid attention to the warnings (they are in there, but buried a bit... Really they should have had giant font, red print, and a sticker inside the calculator)

If you decide you don't want to fix it yourself, drop me a line... I am looking to acquire a 29C myself.

By the way... Please tag that charger "DO NOT PLUG IN --- WILL DAMAGE CALCULATOR" so your heirs do not make the same mistake. Most people nowdays do not risk using that charger and charge the batteries (replaced with modern NiMH AA) outside the calculator in a modern charger.

Good luck and let us know what you do.

[Bill Duncan]

I agree, the hp29c was a gem, except for the charging..

[sgansky]

Thanks for the input. I'll check out the German site.