An EICO 242 FET VOM Part 2: Resistors?
Tuesday, September 1, 2026 at 07:38:14
Some time ago, an EICO 242 VTOM came across the bench. While I wasn’t going to do anything with it, I decided to see if I could bring it back to life.
Here’s the issue:
The DVM is measuring 20VDC, the EICO 242 is measuring the same voltage, but reporting only ~17VDC. Something is wrong here.
It’s probably one or more of the following:
Out of calibration
Resistors out of tolerance
Switches are very dirty
Some unseen damage
There’s not a whole lot in this device. Let’s check a few resistors:
The first one is supposed to be 90Ω, the second 1.227MΩ. They’re actually pretty good.
I did about half a dozen, and all were like this - quite well in tolerance. Hmm…
The switches are really blackened from age, so I’m going to give them a cleaning and then do a calibration. We’ll see what that does for us. If it gets the meter “good enough!” I may leave it at that…but I’d still like to go through the resistors just to see what’s what, and there are a few small electrolytics in there that certainly need replaced. Stay tuned!
Previous part of this series: https://wereboar.com … an-eico-242-fet-vom/
Wrapup and final thoughts: Coming soon.