Eico 666 tube tester and 12AU7s help

stork123

Active Member
I was recently testing some 12AU7s using the roll chart on the tester as a guide. After getting through a handful (that all tested really strong) I packed it in for the night.
A couple days later I was testing some power tubes using the most recent chart from 1978 that is online. When I tested some of the same 12AU7s using the updated chart with different settings, they tested much lower.
I then decided to try the supplemental tube chart book that came with the tester and the same 12AU7s tested in the middle of the first two tests.

I assume that the most recent chart from 1978 would be the most accurate, but why would the results differ by such a huge margin.

The tester was recently recapped.

Thanks in advance for any input.
 
All of the incorrect setting for that tester was one of the reasons why I got rid of mine.
 
Also do a search under Eugene Dunn. I think he's at the Telecaster site TDPR?, and maybe Antique Radios.
 
I´m attaching a XLS file that I´m sure will be help you.

I used it to test my valuables ecc83 mazda,telefunken and mullard tubes

The 12AU7 also is there

Hope this helps.

Regards

Luis
 

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Another problem rarely discussed about the these testers are the variations in the heater voltage.

I have a couple different testers from different manufacturers and some tubes just test low on one tester but test well on another. Design differences can account for much of that, but the truth is- regardless of how well tube tests, the real test is in the circuit you are using it in. Growing up, we had a color TV that would eat tubes about once a month. This was close to the time when the testers were getting pulled out of most drug stores, and those that were left were still rather expensive (for the time period), so to save money I would put the best tested tubes into the critical locations, and the lesser tubes in the less critical locations without need of buying any more tubes unless one completely failed, and then the set stopped eating the tubes as often, at least until the picture tube failed, but it was a situation where I was swapping in marginal tubes one at a time until I got the set working again. I also have an AA5 that every tube in it tests at about 30 on most emission type testers, and the radio works very well, and is very sensitive even with the ailing tubes (based on what little information was on radio and the soldering, I suspect it was a kit, either from a vo-tech, or home built kit.

So, to make a long story short- you can use the tester even with erroneous settings or settings you are not sure of for balance checks- and if it passes that- use it. 1978, remember was the end of the line for many tubes, and most of the manufacturers were wanting to dump their inventories- and higher or tighter standards to create a higher failure rate meant people went through more tubes than they needed to. The tester manufacturers were keenly aware of this.
 
i dont understand the Hoffman chart because there is more lever numbers in the chart than there is on the actual tester
 
Conrad's chart is for the Eico 667, which is basically the same machine but with sockets that have more pins, thus more switches. Just ignore the switches that don't exist on yours. The settings are the same otherwise.
 
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