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Eico 235 VTVM
#1

I have gone through the whole meter and replaced all parts needed. The meter works but when referring to the manual it states to adjust R23 to get a zero meter if you don’t when selecting the function switch. I tested R23 it reads around 11K but when testing to adjust the zero needle it does nothing.Also thinking of a battery eliminator circuit to replace the D cell battery.


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#2

Hi. It's important to remember that the potentiometer may measure 11K, but a measurement should be taken across one of the end terminals to the center terminal while moving the control through it's entire swipe. Look for a smooth change in resistance. Quite often the wiper will have dirt and have intermittent contact. This can usually be corrected with an electronic cleaner spray. Here's a link to the battery eliminator I have used in my meters.
https://forums.qrz.com/index.php?threads...it.650848/
I have also used the LM317 adjustable regular circuit but this one works very well and is simpler.
#3

Hi Rod, I did clean all the controls with contact cleaner and measured resistance from the center to the outer terminals and from outside to outside. The pin 1 and 2 measure from 3 ohm to 11k with 2 interruptions while turning no reading then resumes while turning. Finding one like it should be fun. Thanks for the link ill check that out.
#4

With 2 interruptions it's defective. It will have a tendency to fail right where the wiper sits for long periods of time. You might be able to take it out, remove the back cover and inspect the insides. Not usually a difficult task. You just have to be gentle pulling back the cover prongs. If you get the cover off use some alcohol with a soft brush to gently wipe it clean.




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