Got an Emission tube tester...

[ic-racer]

My brother gave me an EICO 625 tube tester as a gift. He had too many of them.

I cleaned it up. Replaced the lamps that were burned. Fitted a new window for the scrolling list, fitted a new power cord and carrying handle and checked out all the innards vs. the schematic.

It is a little bit of a voodoo apparatus from the 'Tube Equipment Service Technician' era. "Ma'm you need new tubes, your tubes are weak..."

[ic-racer]

Here it is as I got it:
[IMG768]http://img.photobucket.com/albums/v670/ ... file-4.jpg[/img]

[ic-racer]

This is after fixing it up:
[IMG768]http://img.photobucket.com/albums/v670/ ... file-7.jpg[/img]

[ic-racer]

For those of you that don't have these I'll explain what it does. Each of the levers is connected to one of the numbered pin sockets.
The top position is the applied B+ for the test (adjustable from 120 to 20 or so, depending on the tube).
The middle position is the heater voltage (adjustable).
The bottom position is the ground.

To make it work you connect the plate, grid and just about anything else to the B+. Connect one end of the heater to heater voltage and the other end to ground. Connect the cathode to ground and it measures the current through the tube with the tube as a diode. Since the grid and plate are both hooked together, this current has nothing to do with in situ parameters like bias current or transconductance.

What is normal? Whatever a new tube reads. So there is a 'fudge factor' knob on the left called "Shunt" that will make the tube read whatever you want it to read on the scale

You can work through the fixed resistors in this thing and 'blueprint' it so your results from new tubes match the scrolling chart. But since there are only a handful of tube types I'm likely to test, I just made up my own chart of what is considered 'good.' For example on this unit using the supplied settings for 6CA7, all my EL34s (including new ones) read 'weak.' This was easily cured by revising the setting of the "Shunt" knob from 15 to 18 for future tests. That little change brought all the tubes into the green.

[Structo]

I have a Simpson that is similar.

Of course after I spent $200 in a bidding war, it doesn't seem to want to work on 12ax7's, the reason I bought it in the first place.

Probably one of the push button switches is bad.

[Firestorm]

These can be useful, but kind of a one-trick pony. They only measure whether the cathode is emitting enough electrons at the B+ and heater voltage you set.

[Reeltarded]

But it looks like mad science so I like it. I would be lost with actual test equipment. I just use an amp.

[Prairie Dawg]

You've got a nice bunch of original Dakaware Tele tophats there too. Was yours factory wired or home built? they were sold as kits.

The 625 is a good, reliable emission tester and very useful for weeding out shorted glassware. I bought five of them for $5 each one time a few years ago, repaired three and sold them and scrapped out the other two which is how I acquired a lifetime supply of tophats.

Now here is where it gets interesting. One time I took a brand new 6L6GC and burned it in and tested it on my Hickok tube tester. Then, with a protractor I carefully measured the deflection angle of the needle.

Next, going to the 625 I set the same tube up and adjusted the load control to produce the same angle of deflection. I wrote it on a card.

Then I proceeded to test a bunch of 6L6s on my Hickok and my cheapie Eico 625 using the noted deflection angle and you would be really surprised at how close the results were.