Precsion model 640 tube tester

[DavGoodlin]

I just got this with the deal when I went to pick up a 1935 RCA console 9K1.

Assuming its merely an emissions tester, it may be helpful to keep around for the oldest 4-6 pin tubes.
Precision 640.jpg

[TVTim]

Reminds me of days at Radio Shack with my dad.

[Olorin67]

"Cathode conductance" on the front panel: Yep, its an emissions tester. Still good for checking for shorts and seeing if used tubes have life left in them.

[DavGoodlin]

This may be a good replacement for my 1977 EICO model 635, an even simpler emission tester. It was great to pass-fail batches of tubes so I did not keep the truly bad ones around. I wore out both 9-pin and compactron sockets on it. I also fried its power transformer trying to "rejuvenate" beam-power tubes by crankin the filament voltage up

I am looking for a good tester to complement my Weston 798, dated 1948. Its a decent mutual conductance tester for anything up to that date.
It seems like there are only a few choices from Hickok or B&K for testing mutual conductance on newer tubes.
None of the shops I worked had a good tester and relied upon the set, assuming a replacement tube was handy.


I started testing tubes at RS, it was a good way to kill time while the folks were shopping. I few other places had testers in the mid 70s but RS had a less abused one.
Tim- want a Heathkit TC-1? You can get started on tube stuff next week

[Tubejunke]

I'm not sure how many Hickok models it works on, but the company made an adapter to allow testing of the (then) newer compactron types and others that came out in the 60s. I know my 6000A came with either that capability or the backward compatible version which would test the old 20s-30s "big pin" tubes which I simply keep around an old 40s Sylvania tester (emissions) for.

[Olorin67]

most tube tester makers sold accessories to test tubes with more pins on older testers. If you see tube data in your roll chart for 12 pin tubes, and your tester doesnt have a socket for them, an adapter is needed. Usually this is stated on your set-up chart.

testing tubes in the set is always preferable, if you have a known good tube to compare with. thats the only way to confirm that a tube is good enough to work in your set A lot of times a tube that tests marginal will perform just fine in a set, but some circuits are finicky, and even tubes that test good will not work in all circuits.
Still good to have a tester, even an emissions tester, to weed out tubes with weak cathodes, or shorts. And if you dont have a stash of replacements for every tube in your sets, a tube tester is valuable to see if a tube might be an issue so you know what tubes you need to buy. I have a lot of tubes on hand, but a lot are used pulls I got at hamfests, so I always check them before I sub them in a set to see if there is improvement. I have a Hickok 6000a that covers modern tubes and compactrons, a Hickok 600 that has pre-octal sockets, and an old weston that tests early tubes. you cand find testers in odd places, I found one at a junkyard/surplus dealer, the 6000a for $40 at an antique mall (next to a cheap Knight tester with a nicer condition case for 3 times the price), and the 600 from a co-worker who heard I fixed old radios, and was cleaning out an estate.