HP35 problem with a calculator, maybe due to a faulty charger
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03-22-2021, 04:55 AM
Post: #21
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RE: HP35 problem with a calculator, maybe due to a faulty charger
The Woodstock and later chargers aren’t regulated, but I thought the classic ones were (yes, they can fail; so can a bench supply, although it is probably less likely and also easier to figure that out before it’s too late). Then again, no supply may resist a lightning strike…so, yes outside of the calculator is best. Tough for the 19c as the only thing that fits is an HP-10 which doesn’t have continuo us memory, but also won’t resist a lightning strike and is harder to fix/replace than the 19c.-kby
(03-21-2021 03:50 PM)mfleming Wrote:(03-21-2021 09:37 AM)ThomasF Wrote: as chargers becomes more and more unreliable, do you know the best way to charge battery packs outside the calculator? |
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03-24-2021, 08:55 PM
(This post was last modified: 03-24-2021 08:57 PM by aurelio.)
Post: #22
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RE: HP35 problem with a calculator, maybe due to a faulty charger
(03-21-2021 06:52 PM)teenix Wrote:Thank-you Tony and thank- you Harald and congratulations for the HP Classic upgrade kit - Multi Emulator project .......I missed it when it was published, a few years ago(03-21-2021 04:43 PM)aurelio Wrote: Well, if the voltage on test point is the one expected it means maybe that the PSU works properly, so what would be the next step in the troubleshooting? I'll follow your advices and meanwhile I'm "playing" with the faulty board with the presumption of understanding something more. Yes maybe when i press a digit key "the display is turned off [....] it is possible the code is still running but in a dodgy loop that makes the calculator look dead.", I checked the test points and found alll the values of the calculator "on" and this maybe is a confirm that there's not been a power reset... |
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03-24-2021, 11:08 PM
(This post was last modified: 03-24-2021 11:08 PM by teenix.)
Post: #23
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RE: HP35 problem with a calculator, maybe due to a faulty charger
This is the HP-35 reset circuit.
It would difficult to test without an oscilloscope. cheers Tony |
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04-01-2021, 06:23 AM
Post: #24
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RE: HP35 problem with a calculator, maybe due to a faulty charger
Related to this, and with my fear of using the old chargers in my calculators, I modified and build my own charging pack.
I followed the information on this page: https://davidreaton.com/hp-calculators/h...-chargers/ Replaced the resistor (and the capacitor) to lower the charging current from the charger, and built my own external charger with led feedback. Right now I just built it on a prototype board, but will make a better box for it when I get the time ... So now I can slowly charge the NiMH batterypacks outside the calculator in a safe way Cheers, Thomas [35/45/55/65/67/97/80 21/25/29C 31E/32E/33E|C/34C/38E 41C|CV|CX 71B 10C/11C/12C/15C|CE/16C 32S|SII/42S 28C|S 48GX/49G/50G 35S 41X] |
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04-01-2021, 05:50 PM
Post: #25
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RE: HP35 problem with a calculator, maybe due to a faulty charger
(04-01-2021 06:23 AM)ThomasF Wrote: Related to this, and with my fear of using the old chargers in my calculators, I modified and build my own charging pack.thank-you Thomas I know that interesting site that iis the same Ivisited and linked in a previous thread The circuit has been rebuilt using modern transistors nowadays available |
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04-16-2021, 01:34 PM
Post: #26
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RE: HP35 problem with a calculator, maybe due to a faulty charger
Hi all, it is definitely a CPU board problem, I will investigate forward, when I will reach the skill to do it
I enjoy for now the Tony-Harald's emulator which brought my calculator back to a new normal life The normal life which we all dream, and will be after this pandemic sufference period thank-you very much Aurelio |
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