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Hp 25 LED brightness
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04-10-2022, 10:08 AM
(This post was last modified: 04-10-2022 10:09 AM by teenix.)
Post: #3
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RE: Hp 25 LED brightness
Not really, the display power it tapped from a coil in the switch mode power supply.
I measured about 4V volt on a voltmeter on pin 5 of the ROM0 chip which is Vdisp. If you think it is too low and the battery low LED indication is not active then you may consider replacing the capacitor and/or diode coming from the coil connection that supplies Vdisp. The potentiometer is there to adjust the battery low level sense for the Cathode Driver. Mine is set to 1.18V into pin 4 of the Cathode Driver. If you have been twiddling the adjustment, this may not be set properly now. The HP-25 schematic can be found here... http://www.hpcc.org/cdroms/schematics5.0...k/hp25.pdf cheers Tony |
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| Messages In This Thread |
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Hp 25 LED brightness - Graan - 04-10-2022, 09:34 AM
RE: Hp 25 LED brightness - BobVA - 04-10-2022, 10:06 AM
RE: Hp 25 LED brightness - teenix - 04-10-2022 10:08 AM
RE: Hp 25 LED brightness - Graan - 04-10-2022, 11:53 AM
RE: Hp 25 LED brightness - GreyUser - 04-12-2022, 12:01 AM
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