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Moded my Tube Tester--Confusing Results!

thefragger

thefragger

Certified Crazy.
Hi All!

A little while back I modded my Eico 667 in a way that let me directly read the plate current of any tube while under test.

I thought today would be a good day to test a quad of 6550WE tubes I've had lying around...

These are my settings:

6.3 FIL.....15 GR.....90 PL. (grid and plate are 0-100 scales, in volts?)

And here are my results:

Code: 
"green" tube
123.2uA idle current
600k leakage (14.9uA)
[b]110 merit[/b]
0 H-K leakage

Code: 
"yellow" tube
69.2uA idle current
10M leakage (<0.0uA)
[b]101 merit[/b]
0 H-K leakage

Code: 
"blue" tube
1.1uA idle current
inf. leakage (<0.0uA)
[b]113 merit[/b]
0 H-K leakage

Code: 
"red" tube
28.6uA idle current
2.5M leakage (0.4uA)
[b]110 merit[/b]
0 H-K leakage

All tubes were warmed up between 5 and 10 minutes each and readings were taken after 20 seconds of no change.

I just can't see a correlation between the 'merit' reading and all the other information I thought I needed! Also, 'green' and 'red' tubes test the same of 'merit,' but vary in every other reading!

Am I just confusing myself here?


:scratch2:
 
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I was working on advise from a member on the DIYAudio forums who advised me to tap into the plate supply (lever position four) line to read the current, and to use that as a way to determine the 'quality' of the tube. This is how he matched them for sale.

I simply located the supply wire and cut it into an 2-pole on-on type switch, with one side shorted and the other side to a set of tip jacks. I have it flipped to the shorted side for notmal operation, or flip it to the tip jacks and plug an ammeter in whenever I'm feeling adventurous.

Aside from the few bits of wire, a switch, and the two tip jacks, nothing more was added.
 
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thefragger said:
Am I just confusing myself here?
Click to expand...

Yes you are.

I am not familiar with that particular tester, but you appear to be measuring for leaks only (are you?) and I don't know what "merit" means in that context.

The emissions test and/or the transconductance test (if so equipped) are separate and do not normally correlate with any part of the leakage or gas tests.

As to measuring plate current, you have to ask and understand when to read it (during what test), why and what it means. Only the guy who gave you that advice can answer that.
 
How are you measuring leakage? 667's don't have the ability to measure the wide range you've got listed, so I'm confused.

Also, plate current in the microamp range, like you're showing, doesn't make sense. What are you measuring that with? 1.1 uA is less than your almost-grounded body will impose on a circuit if you're standing nearby. Also remember the 667 is a basic emission tester, and uses a.c. on the elements, so be careful how you measure the plate current, even if the mod you used really does capture it. The TUT's plate will show half-wave a.c., which is technically d.c., but some current meters may not cope too well with that.

I remember seeing a 667 plate current mod, and I'll see if I kept doc on it.
 
I understand the insignificance of the uA scale, but the readings I'm getting increase steadily and with purpose from an exact zero to their 'settled' values, with the pause between one fraction and the next increasing on an exponential scale.

I'll try my best to show you guys my setup.

Here are the external bits of the mod I made
IMGP0004_sm.jpg


Here's the scale on the tester; the 0-140 / REPLACE-?-GOOD scale is for the 'merit' reading and the centre scale is for measuring leakage
IMGP0007_sm.jpg


Here you can see the 'MERIT' spring-return lever
IMGP0011_sm.jpg


The 'LEAK' column in the tube data booklet
IMGP0001_sm.jpg


The typical setup
IMGP0009_sm.jpg


Right at the 6 o'clock position is the uA setting--this meter walks in-step with my Fluke 77
IMGP0008_sm.jpg
 
Hmmm, more questions arise:

Was your 667 a kit, or factory wired?

Do you have a schematic, or link to one, for your mod? Interrupting line 4 is the right thing to do, but everything flows through that, including shorts testing, so jumpers and correct wiring are vital.

What meter setting are you using for current, specifically, a.c. or d.c., and what other experience do you have with the meter on current? What does your Fluke 77 say in this situation?
 
From all appearances it was a factory-wired unit (or a very professional DIYer), diodes were upgraded before I bought it (to my surprise).

Here's the thread from when I first got it, with internal shots in post #4.

I'm working on finding the photos that documented the mod I did... I remember de-soldering a wire from some feed point to the lever, and put two extensions in to get it reach to the switch (in a location to make it look somewhat stock).
 
Good, waiting for those pics, they will help.

Now what about your meter settings when you're measuring current?
 
D'oh! Looks like my meter defaults to DC current reading... might have to run a test before I hit the hay with the meter set to AC current. What a dummy!

At least I've still got my looks.
 
Also, I fear the pictures reside on my main desktop computer, which current is out of service with a dead video card.
 
OK, with the meter set to AC current, here's what I've got:

Code: 
"green" tube
[b]109 merit[/b] (77.0 mA)

Code: 
"blue" tube
[b]101 merit[/b] (71.6 mA)

Code: 
"yellow" tube
[b]102 merit[/b] (74.2 mA)

Code: 
"red" tube
[b]100 merit[/b] (70.5 mA)


Those numbers look a lot better... and I feel like an idiot. Thanks for helping me turn my brain on, keybank!
 
That's a nice tester, for some strange reason I can't get on the tone lizard web site.
I just picked up a Precision 612 with a adapter to takes the Nuvister tubes which I
like.

Tube
 
tube-a-lou said:
That's a nice tester, for some strange reason I can't get on the tone lizard web site.
I just picked up a Precision 612 with a adapter to takes the Nuvister tubes which I
like.

Tube
Click to expand...

Hi,

I have a Preccision 612 and can't get the meter to center, in line adjustment.
Any help would the appreciated.
 
Here are photos of the inside... I got tired of looking for the old ones. Looks like I got smart and use a SPDT switch instead of a DPDT!

Pick-off point (thin red wire on the left of the switch)
IMGP00013_sm.jpg


Backside of the case mod and tie point to position 4
IMGP00014_sm.jpg


Backside of the case mod
IMGP00012_sm.jpg


The tubes I'm testing
IMGP00015_sm.jpg


The tip-jacks I used
2011-02-04-224808_sm.jpg

​
 
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