An EICO 249 VTVM, Part 4: Let’s start the rebuild.
Friday, July 17, 2026 at 21:14:00
I’ve put this one off long enough. It’s time to get this one done.
This unit is going to require a complete overhaul, including every resistor on the range switch (and then some!) So let’s start with the range switch.
Since almost all of these resistors were custom values, I’ve ended up having to make some of them. There’s an easy way to do that, you can use standard values and a special calculator site:
Resistor Finder: https://mustcalculat … s/resistorfinder.php
This site searches standard values and tries to come up with a solution using two resistors. I was able to make all of my hard-to-find resistors (I’ll publish that chart in the wrapup,) except for one. That one was 82MΩ, which is an odd value. There’s limited selection on that one at best, so I made one out of four resistors.
I don’t have all of the resistors I need yet, but I had enough to get started on the switch. This is what I came up with:
I’m going to try and do maybe 5-6 resistors at a time so there’s no screw-ups. This part only has one that needed multiple components, the pair hanging off the bottom is a 325kΩ unit.
This is just going to be a slow process - there’s no way around it. Stay tuned!
Next part of this series: Coming soon.
Previous part of this series: https://wereboar.com … ng-the-range-switch/
Wrapup and final thoughts: Coming soon.
References
The EICO 249 / 232 Manual and schematic set: https://wereboar.com … with%20schematic.zip
Youtube playlist for this device: Coming soon.