New (to me) projects on the bench – Part 3


8) EICO Model 221 Vacuum Tube Volt Meter

Whenever I get a new (to me) piece of test equipment that is older than 25 years I always want to look at the capacitors. They are almost surely leaking. I thought about bringing this up on the variac and isolation transformer to test but honestly I was going to replace the caps anyway.

Looking at the meter itself I find it in need of a cleaning but in good shape. First thing is to take it apart and wash/scrub the case. Ah, much better smell now.



Contact cleaner and a pencil eraser for the switches and potentiometers and we can see they are the original caps.


“Online manual for the Eico 221 here”

So there seems to be an issue looking at the schematic. The C2 filter going to ground doesn’t have a value. Apparently they used whatever they had back them so you would find anything from 1-3 microfarads. I used a 2 μF cap and replaced all the other ones as well.

Seems to work like a charm but I do need to build the probe still. The nice thing about this one is the DC probe as a 15 Meg 10% Carbon comp resistor in series. The EICO 221 has a higher than normal ( good thing ! ) input impedance of around 25 Megohms for DC measurements, and about 3 Megohms for AC.

AC and Ohm share their test leads with DC being separated. AC/Ohms probe is simply a piece of wire with a probe tip, no coaxial cable, nothing special, plain old multimeter-type probe with a pin-jack. The ohms scale provides its own power and uses the 6SN7. The AC rectifies the AC to DC and then uses the 6SN7.


And here is the after pictures:



The resistors seem to have tested fine and I will likely replace those when I build the probe itself.

Ah, the finished product (I am going to have to turn that power switch properly):


Here is what is left:

1) Leader LBO-507A 20MHz Oscilloscope
4) REM Electronics Cathode Recovery and CRT Tester w/ original box 
5) B & K Precision Model 465 CRT Cathode Ray Tester with original manuals
6) Shurite Amperes Meter
7) EICO Model 950A Resistance Capacitance Compactor Bridge Tester 
9) Edwards Signaling Transformer 88-100
10) Vapor Tight Heavy Duty Marine Power Selector Switch 12v 150A/6v 300A Continuous
12) ASI Dynamic Transistor Checker 
14) Louis Marx Model Train Transformer
15) Unknown tester device with old radio bulbs

Have fun and 73’s,

Let me know what questions you want me to address or if anything is unclear. My email is


About K0FEY

I am a member of the Eden Prairie Radio club. This is a Minnesota Ham Radio Enthusiast club and we promote experimentation and learning through the Amateur Radio hobby. Come check into a net on Sunday with us or better yet meet us in person on the 3rd Thursday of the month.
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