Woodstock Low Power
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01-09-2018, 09:39 AM
(This post was last modified: 01-09-2018 04:52 PM by Harald.)
Post: #79
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RE: Woodstock Low Power
Ok, here is an update and a question.
I decided on an HP25 keyboard after realising that actually both, the ON/OFF and PRGM/RUN switch make sense. The main PCB I used came from a very dead 25c, on the plus side the PSU on this was on a seperate board and could be completely removed. On the negative side, the anode and cathode driver spacing was wrong. This is a very late 25C. After realising that the LED display would sit too high if I used the low profile sockets (does this work for others?) I decided on soldering the LP pcb directly to the calculator PCB. After assembly the calculator powered right up and everything looked fine. Then I installed the GPS module and PSU for it and reassembled the calculator. I could turn on GPS, but after a second or so it would turn off automatically. So I opened the calculator in order to measure the power on signal for the GPS-PSU. Hooked up a scope probe and turned on the calculator. But ever since doing that, any key press results in a "0" on the display. Effectively all keys are interpreted as the "0" key. What have I done? Have I shorted something? I am a bit lost now. Cheers, Harald Edit: It is still only the "divide" key that gets the calculator back out of sleep mode. I guess that means the PIC is dead... |
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