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HP3435A DMM switch cleaning
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jupiters_spot:
I have a new-to-me HP3435A digital multimeter that's acting strangely -- the LEDs illuminating the unit enunciators are not consistent with function selection (e.g. Ohms units are illuminated when DC Voltage function is selected). I suspect I need to clean the pushbutton function selectors, but I don't see how to open them up or squirt in some DeOxit. Can anyone direct me to resource on how to clean the contacts inside these switches? They're the spring-loaded switches aligned vertically starting on the #7 of the project pad underneath the unit.
(image linked from xrunner's Excellent post https://www.eevblog.com/forum/testgear/hp-3435a-extreme-makeover/)
jupiters_spot:
I found an article here that describes how to disassemble the switches - search for section entitled Repairing the Push-buttons
J-R:
I was faced with a similar issue on my HP3466A but spraying contact cleaner in through the front of the switches while holding the board vertical was enough to solve it. Maybe someday I will need to take them apart, but for now it's OK. It is absolutely true that the bad contacts will cause the unit to switch to resistance mode.
Fun story on mine, I ordered a vintage & broken Keithley DMM and the company sent me the HP3466A first by mistake. Then they sent out the correct item and told me to just keep the HP because it was faulty. But the only major issues I found were the intermittent buttons and of course bad batteries. It wasn't a vintage DMM on my radar at the time, but I enjoy having it now.
The LED displays are always cool...
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