Having an issue with this tester, I seems when I do the gas test on known good tubes gas reading are too high.

What could cause this?

Any help will be appreciated.

My short answer to your question is that the 600's so-called Gas Test is really not a gas test, it is simply where they remove the Plate from the bunched array (of plate and grids) where the grid(s) are tested for conduction. With a gassy tube, sometimes this will show on the tester, but there are additional reasons for this type of Gas Test to not give reliable results. There is a good reason that Triplett did not advocate incorporating this same Gas Test into their models 2413, 3212, 3413, 3413A, and 3413B (your tester's circuit is a copy of the TTT3413)...it was written into the TTT engineering drawings but never found its way into production units, because this simple of tester is simply not capable of testing for Gas. IMHO, the Knight Gas Test scale may have been there for advertising/sales purposes. Triplett also published a procedure to "match" tubes, but it found its way only into the earliest production model 2413 instructions, as it was found unreliable.

ok, sounds good Fred.

Another question if I may. It has to do with it's 7 pin loctal socket. I have yet to find any of these testers where the 8 pin loctal socket had snug pins.

Am I missing something here? Have you seen this?

You asked "I have yet to find any of these testers where the 8 pin loctal socket had snug pins." I don't know if I've seen this problem, but many of the loctal tubes (both nos in the original boxes or previously in use) I've seen have difficult-to-remove layers of corrosion on their tube pins...so even a good loctal socket may not make contact with the pins until you've cleaned the pins. If you need a type of loctal replacement socket, ask in Classifieds, an ARF member might have it.

A good loctal socket should lock-on to the tube's center metal stud, preventing it from falling out of the socket. But some people damage the sockets (which may be the problem you've described) by forcing/pulling the tube any which-way to remove it from the socket. There is a correct technique to remove a loctal tube from its socket that doesn't stress or bend the socket's metal contacts; it involves pushing the tube-top slighly in one direction to unclick the lock before pulling it out. It doesn't hurt to apply a thin smear of grease (vaseline, etc.) to the tube's metal stud which helps with later removal of tube. You can easily test each of the eight contacts by using the smooth (not the fluted-cutting end) shank end of your #56 drill bit (which is same diameter as loctal pins), running it through each of the eight contacts checking for tightness/electrical contact.

Good tip!

Thanks Fred.