An EICO 249 VTVM, Part 9b: The AC Input.
Tuesday, August 11, 2026 at 07:35:34
I didn’t feel like fussing with switch connections last night, so I sat down and worked with the AC input.
Originally, the line cord flew directly into the unit, up to the switch, and back to a terminal. I didn’t want to do it like this, so I added a new terminal and took the old one out for later reuse.
I also wanted to add an across-the-line capacitor to help catch any noise in this device, since it didn’t have one originally. I had to think about what I wanted to switch here, and I thought about doing the neutral - but after consideration I didn’t want the transformer to be hot even when the device was off, and I felt there was enough isolation on the power switch that I could safely switch the hot side. I did the neutral thing at first, but pulled it out and re-laid everything hot.
You can see that I had to clean up the transformer lead a little because it was cut short. I ended up just lifting the transformer out and lengthening this wire a bit.
Everything laid back in without issue, although I did cut things shorter when I put it back in with hot switched.
The AC will now come in, hit the terminal strip, and fly up to the switch and back from this terminal.
The only thing I don’t like about this is the AC has to be in the air. This was the original design, so I’m trying to mitigate a little. The chassis is already busy, so I wound the to and back lines together with a ground lead, hopefully to minimize the noise levels.
We’ll see if this does anything.
Next part of this series: Coming soon.
Previous part of this series: https://wereboar.com … part-9a-the-rebuild/
References
Manual set: https://wereboar.com … with%20schematic.zip
Youtube Playlist: https://www.youtube. … k&list=PLbV6LYdZISZI
The playlist has more videos scheduled for much later, there are several months difference between here and YouTube.