The lay of the land Message #10 Posted by glynn on 18 Apr 2003, 7:45 a.m., in response to message #6 by Paul
Paul, sir, the old HP that developed, sold and serviced calculators and such, has gone through many changes, layoffs and "re-invention" cycles over the years. Many of us here lament that, but that's part of the reason for belonging to a community of enthusiasts and collectors. Unlike HP, which offers NO support to products beyond its "support life", those of us here who CAN help each other, try VERY HARD to "steer" the owners of our favored calcs in the right direction.
It may well be that you will send off your 25c to someone to do the diagnosis and repair-- but NO ONE that I know of can claim the certification by Hewlett-Packard, to repair machines older than their End-Of-Life date. HP's attitude is similar to that of many companies these days: you merely need to throw out the old, and purchase the current offering.
If the product, considered now "disposable" by everyone in "certified" worlds, is only held onto by collectors and caring users, it will be difficult to find a "technician."
If the only parts available are "cannibalized" from other machines, as would be the case for a 25c, and the only people who care to DEAL with a 25c in the present are those who love them and make it their hobby, then I personally would say, your best-case scenario is that one or two here at the MoHPC forum would qualify "ex grege"(from the flock), not "ex-oficio" (having the title), by virtue of their having enough experience, knowledge, sense and decency to help you out.
TO reiterate: HP does not certify technicians for repair of these machines, and back in the long-ago day when these machines were supported, they were generally supported by a repair depot in Corvallis Oregon that no longer exists. If you must find someone whom you have more inherent trust in than those here, perhaps HP itself can point you to a facility it recommends. But I think a call to the service organization will confirm: your 25c is no longer considered a repairable item.
So, what do *we* do, here at MoHPC? We recommend, firstly, that you be willing to LET us help you by doing some troubleshooting from afar.
The 25c has no "diagnostic mode", but symptoms of various failures often point to the flaw. Knowing definitely about it is a matter of YOU making measurements, describing the situation as it exists, and being willing to follow recommended procedures.
Believe me, no person regularly here would EVER say anything that would lead you to risk the health of your calculator. They love these calcs too much to throw out their caution. They will ask questions and come to a conclusion based on the facts you can give. Sometimes, the conclusion they come to is that THEY have the ability to do the repair, in which case they'll make the offer to.
In MOST cases, people find that, if they are not too quick to pass on the advice offered, but actually engage in the process, that they themselves can get their calculator healthy again, repaired and restored. You will find many testaments here, if you stick around, of people who have been given advice, taken it, and had a happy result.
Here at the Forum, many of the respondents have EE's, doctorates, parchment of various types you'd be SO LUCKY to have paying you attention at any repair facility anywhere. There are self-taught technically-minded EXPERTS with no certifications, degrees or pedigrees OTHER THAN they have proven to be deeply committed and involved in the loving repair and restoration of these classic machines. Again, you should BE so lucky to find such expertise anywhere else.
The 25c is a good and generally robust machine, but it DOES have something of an Achille's Heel: the machine can eventually die a permanent, ugly death IF it receives too much power for too long by using a power supply meant to charge AND power the calc, WHEN the battery is not there, making bad connection, or otherwise disabled.
The advice most people will LOOK to give first therefore, will NOT focus on checkout of your CPU or display drivers; you have given them a reason to focus on the machine's most common failure points, so listening to them can SAVE YOU this machine, and continuing to use it WITHOUT following their train of enquiry may make us all sad.
Now *I* will offer some specific hardware advice. This is based on some things you have said. It is not offered as "expert". Peer review will be valuable, so other input is solicited.
1. You rebuilt your own battery pack. Fine.
2. You can operate the calc on AC power. You say the pack is not charging-- this implies to me that the calc, when on batteries, removing the charger, is not functioning.
3. You say you have tried another charger, and your theory is that one charger could have been bad, but two won't be. Although that logic is flawed, in my experience with chargers, I believe you are correct that they "work", because they turn on your calc. Verifying AC voltages would, nonetheless, be a GOOD THING TO DO.
4. Given what I have heard SO FAR, I would ask: have you checked your pack's connections? Have you checked that the connections BETWEEN the pack and the calculator (the "contacts") is secure? Have you sanded them lightly to remove corrosion? Have you put bits of aluminum foil between them and the contacts (small little intervening folded strip, just to see if contact is being made securely?)
I am suggesting that the calculator is not "seeing" the batteries, either because one or more of them are defective, or because the contact between pack and calc is not sufficiently made.
YOU can at least look at those possibilities, I am sure. The successful result would be batteries in the machine that DO charge, and subsequently run, the calc. Charge with the machine OFF, please.
Now let me tell you a little more about that Achille's Heel. IF you are not charging batteries because they are not properly connecting, they cannot act to "buffer" a little transformer which is not very "smart". WITH a sufficient load on it, the transformer puts out the right voltage, right current. If the battery does not exist in the circuit to put the proper load on it, the power supplied to the rest of the calc is a bit too much, but still passably regulated in most areas EXCEPT ONE: the "Continuous Memory" chips. If they are supplied extra power for long, they will die. You will not find replacement chips for them on the open market. A donor calc would have to be found, and those with functioning memory chips are damn scarce.
It seems possible to me that flickerinng in the display is a result only of poorly-regulated, "unbuffered" power due to a defective/disconnected battery pack. But BEWARE!-- it could ALSO mean that your memory is being adversely affected. I believe the damage you cause by operating the calc, if it has not got a healthy battery, is cumulative and may quickly become fatal. So, if you take away no OTHER advice, take this PLEASE: Turn off the calc and don't use it as a "desk" machine, not until you've investigated and resolved the issue of non-charging batteries.
By the way, Paul: we're folk who love what we do-- so when someone asks a question of us, we will point you in the direction we think will prove worthwhile to you-- but we are also people who sometimes take umbrage when someone comes in expecting one of us to be wearing an HP badge or waving a diploma from "HP School". Those of us who stay here, make it our home, know that listening to most of the regulars here is MORE valuable than what you'll find in your hometown (and a lot cheaper, too!)
Most of us here know Tony Duell to be one of the most capable, electronic-saavy and knowlegeable voices in our community (if I were LOOKING to get myself a diploma in vintage calc repair, I would go to Tony to teach me, and I'd show a diploma signed by HIM with pride)-- and know David Smith and Trent Moseley to be valuable and experienced members fully able to help; in fact all three have proven their help over and over, as many others here have. Some of the crowd here are experts at one model, others are widely-experienced. If you have friends/colleagues who need assistance with vintage calculators, do tell them about the community here, for we exist to further the future of these old machines and their use.
Thanks. Let us know what you find.
---glynn.
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