HP97 The journey begins
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05-05-2019, 12:08 PM
(This post was last modified: 05-05-2019 12:13 PM by teenix.)
Post: #82
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RE: HP97 The journey begins
(05-05-2019 11:04 AM)Robert VM Wrote: I may have misunderstood... There aren't any original logic chips remaining in the new CPU board. The card reader runs on GND and 6V only, plus Vbatt to run the motor. The cathode driver is Vbatt and GND and the display anode driver has just GND and a current source to keep the LEDs lit properly with variations in battery voltage. I think these are all probably bipolar chip types. The card reader might be different as it may have to connect via internal CRC logic down to the -12V rail - not sure as there are no details. Either way, there is no PMOS logic that I am aware of. I'm just guessing about the 5.5V. The 6 volt to the card reader may be there just because of the available 6 volt rail for the PMOS, so it might be happy with 0.5V less to operate on. I'm not sure I want to experiment on how high the voltage can go with an unregulated supply. cheers Tony |
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