- 2026
- Jan
- 2
An EICO 902 Harmonic Distortion Analyzer Part 2: A well used unit.
In the first part of this series, we discovered that the power switch in this unit was bad. It also needs a fuse, so let’s replace that first. I have some of these old Seneca Fuses laying around - Seneca, of course, being a company that was based right here in Columbus before being acquired by a company called Russell Industries, and lost when that entity closed. These particular ones were made after the Russell purchase, but whatever. They’re fuses.
In order to do some basic testing, I’m going to just jumper the switch for now.
This time, we get glow.
Power supply ripple is well within acceptable range for 330VDC.
The regulator tube is doing it’s job.
The first thing I notice, however, is the meter is bouncing around. Just tapping switches makes it move, so they’re either very dirty, or worn. In particular, the main selector switch, that of being able to select the range, seems very touchy. I can see there’s a groove worn into the brass, and the remainder is very dark with oxidation. That’s not good…it’s got a lot of precision resistors soldered on to it, and would be almost impossible to source. Being the main switch, I can see where it would have had a lot of use.
But, since the power switch is known bad, I’m going to pull it, tear it down, and see what we can do with it. It’s an assembly made of various components marked Clarostat, so it will most likely be able to be torn down - and it is.
The problem here lies in the final piece on the right. That’s the business end of the power switch, but the actual issue lies under the phenolic wafer. There’s a piece of brass there, and it’s most likely worn from use. I can’t get it out because the switch itself is riveted together. Were this 1970, I would simply purchase that piece - but it’s not. I’ve sprayed and cleaned it the best I can, but it’s not giving me anything but some high-resistance wobble when I move it. Back together it goes. I’m just going to tie the ends of the power cable together and cover them for now. The power switch on the outlet strip will work as it’s power switch for now.
After some experimentation and cleaning, the range selector is very tired and worn. It’s quite noisy, and just touching it will make the meter slam to the right. I don’t think any amount of cleaning is going to help this, the brass is just worn away.
I’ve also noticed that some of the tube sockets are very worn, and a simple touch will make the meter go nuts. That’s not good either.
This unit certainly didn’t sit on a shelf and look pretty, and due to the number of components that are worn out, it may not be a useful project. I’m going to put it back together for now while I decide what is going to happen to it. Unfortunately, not every device can be saved.
Stay tuned!
Next part of this series: Coming sometime, perhaps.
Previous part of this series: https://wereboar.com … rt-1-whats-going-on/