Re: Testing tubes

Do you have the paperwork for the Eico? And you are absolutely sure
that all switches are correct? The odds of all six 6AU6s being bad in
the same way are slim, but not none if they all came from the same
source.

But I know of no testers where the SHORT condition happens with a
*good* tube and all knobs are passive (that is in the plug-in condition
and no test button engaged).

Get hold of a manual, that will answer most of your questions. It may
be something as simple as a fouled socket.

One more thing, the EICO 625 is amongst the simplest of emissions
testers. That means that it will not tell you much more than the very
most basic condition of the tube, and even that in a marginal way. Put
another way and assuming that the tester is functioning properly:

BAD on the tester is 80% likely to be bad in circuit.
GOOD on the tester is 80% likely to be good in Circuit.
"?" on the tester is 60% likely to be good in circuit.

Assuming the tester does a creditable job for "Shorts" and "Gas".

On the other hand, with the very best MC testers, those figures run to
99%, 98% and 90% respectively, same caveat for shorts and gas.

The above figures based on personal experience with NRI, Simpson &
Heath emissions testers, and Hickok & Eico MC testers.

There are manuals to be found on-line:

http://bama.edebris.com/manuals/eico/625

Being one of them.

Peter Wieck
Wyncote, PA

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