Eico 232 VTVM & GetBack Tester

SCompRacer

Picked up a non-functioning Eico 232 vacuum tube voltmeter cheap. Figured if it can't be repaired, it would look kewl sitting on a bench. The guy also had this Flyback tester which was used on TV's. This gear reminds me of my Uncle Bernie who fixed TV's and tube gear back in the day. He was my first electronics instructor. Tubes are 12AU7 and 6AL5.

EICO was around from 1945 until 1999 and produced equipment in both kit and assembled form. They are kind of like a box of chocolates.

This 232 was in nice shape on the inside. The battery hadn't leaked acid and still had 1.35v in it. You can tell it had been worked hard as the paper caps were sweating badly. The function selector, part 60025, was broken. I picked up a poor condition donor 232 locally for ten bucks. The selector was good. It even had the more robust function selector, part 60067!

I replaced the five caps, four film and one electrolytic. I downloaded an assembly manual and checked for proper wiring and assembly of resistors. I tested the resistors, and they were all good. The line on the end of the film caps indicates outside foil and were installed with line or outside foil to low impedance side of the circuit. Some folks claim it doesn't make much of a difference. IIRC Ken had shown us in one of his threads how he checks for the outside foil end of film caps.

I splurged on Vishay for most of the caps. They don't make the exact .025uf value so I piggy backed the two .022uf with .003uf. What surprised me is they had the outside foil end marked with a line. I tested them with my scope and sure enough, the line indicated the outside foil.

I lacked the correct resistors to replace the Selenium rectifier mounted on top panel. Output of the original was 47v (spec is 50) so I left it in until the next Mouser order shows up. Folks typically use a 1N4007 diode with a 200 Ohm resistor to get the correct voltage.

I disassembled and cleaned the probe. It switches between AC/Ohms and DC. The 1 meg resistor in the probe for DC was still good. I left it on a for a couple of hours and recalibrated it. Eico suggests a minimum of two hours but suggests 36 hours of warm up before calibrating.

It works!

pitdogg2

Shore is purrty!

heiney9

Amazing!

SeleniumFalcon

Very nice restoration job, Rich! I love the plexiglass back of the meter, nice. VTVM's are still very useful for all kind of applications. The probe looks in great shape, most of the time they're pretty banged up.

SCompRacer

Thanks for the kind words! Some sellers don't even have the probes. I've seen folks make separate probes, adding the resistor on the DC probe.

The probe just needed disassembly and the copper straps/contact cam cleaned. For folks that didn't know, you rotate the probe tip for AC/Ohms and DC measurements. The DC selection adds a 1M(ega) Ohm resistor located above the copper contact straps.

SCompRacer

Finished the Eico 232 project. Replaced selenium rectifier with a 1N4007 diode. Used existing hole for selenium to mount terminal strip. A 330-ohm 2-watt metal resistor gets me close to target of 50vdc. IIRC the selenium was ~ 46vdc. The line voltage is down today too, 118. We are typically at 122-124vac.

A seller on ebay offers a battery eliminator for the 232. You use the Eico 6.3v supply to power it. Maybe a future project...

pitdogg2

👍👍👍

JayCee

Awesome, Rich. Don't know if you remember speaking w/me @ PF '12 but I almost went down the DAC build rabbit hole after following you on-line and our passionate/interesting discussion at Polk HQ. Ended up buying a nice DAC, rather, but it's always been in the back of my mind that I'd wished I had done it. Equally, I really enjoy all your posts.

SCompRacer

Thanks for the kind words!

Now that you mention it, I had to excite a few brain cells and do recall. I learned a great deal about digital building DAC's and trying different inputs, output boards, etc. When you DIY, you (and/or the forums) are tech support...lol Twisted Pear is folding as Russ White is no longer interested or affiliated so there will be no new DAC chip offerings.

I finally bought a DAC myself! I have a Gustard R26 with Singzer SU-6 DDC. The DDC provides USB isolation as the R26 doesn't. The DDC also has better temp-controlled clock. DDC sends I2S over HDMI to DAC. The R26 also has a LAN input which I'll use when my server quits.

I still have the Sonore Server with external power supply, SOtM USB card with external PS. I upgraded the CPU and memory, installed SSD drive for op system 6TB spinner for music. I was able to chuck vortexbox as Roon Rock op system worked on it. I use Roon to convert PCM to DSD512.

Looking at your sig, looks like you are doing OK!