Knight 600c Tube Tester

[icenine]

This weekend a tube tester fell out of the sky and into my hands so to speak...
its a Knight....does anyone know if it is possible to test a (Fisher )7868 tube on this and the settings? Thanks...this thing is pretty cool.




DUH I FOUND IT ON THE CHART I AM A BIG DUMMY SORRY GUYS!

 

[icenine]

Well I can do an emissions test and all my 7868s test good....but from what I can tell I cannot test for a gas test...can the tubes still be bad if they are scoring low on the gas test....my right channel just drops away after about 5 minutes of playing my Fisher 400...
one of my 7868s has a black scorch on the side of the glass...
thanks everyone

 

[larryderouin]

Take a couple of pictures of the tubes. It could be just the getter is dark which in of itself isn't bad. If the getter is WHITE, the tube has lost vacuum, get rid of it.

(Damn Corpsmen!! RTFIM!! WTFA!! LOL!!!!!) = READ THE F$@%ing Instruction Manual. Write the F#$^ing Answer. You know the rest!!!

Yeah the tube can be weak or bad, with a low gas test. It could be just plain worn out.

I just had to ping ya, Icenine.

Larry

 

[icenine]

Yes Larry you are correct I was just testing tubes with that so called "On the Job Training" along with the immediate benediction of the PQS l that I am sure you remember....anyway you are right I will just break down and buy some 7868s from Electro Harmonix....although unless my tube tester is mistaken nearly all of my 6AU6 tubes are bad except for one....
by the way there was an earthquake just before this post!!!
heres a picture but I do not know what a getter is lol
take care
Robbin

 

[larryderouin]

ROFLMAO!!! OH YEAH, OJT & PQS!!! FUN FUN FUN!!

The getter is the silver, or black coating you see on most tubes. It's an indication that the vacuum is intact. When they vacuum it, and heat it up, the material the getter is made from FLASHES against the glass, and absorbs impurities. Depending on whether it flashes fast or slow will depend on the getter being silver or dark, like a black silver. If air gets in the tube, then the getter goes WHITE. NO GOOD! Also the getter is deposited either on the top or the side.

Your 7868 looks to have been FUBAR'ed. The Getter is on top as it is on all the other tubes shown. The "C" shape looks like a burn. Tube had a overheating episode, or had a runaway (china syndrome!). Hold on to it just as a curiosity and attention getter (this is what can happen...........).

Check the BIAS on the tubes also. Good call on the EH's. Good tube.

As for the rest of the tubes, have you checked them against another tester? It could be your tester tests that particular tube and gets a low reading. Some do that. My Eico 625 reads 12A*7's as 55-60 (weak to good) even tho a Hickok with a calibration tube tests them to 80+ on the meter. I'd check the tubes on another tester, and see if there is a calibration procedure for yours and have it checked.

Larry

 

[Tom Bavis]

Not much to calibrate on a Knight 600... there's a pot for the "Line" setting and that's all folks! The so-called "gas" test is of VERY limited value. More info here: http://tubesound.com/2008/05/31/knight-600-tube-tester/

 

[icenine]

Thanks Larry your post was very informative....yeah I think my 7868s are done for like you said....I think it will be difficult to find another tester but I just bought a lot of 6AU6 off of ebay which according to the seller tested fine on his tube tester (TD-55) so I will at least be able to compare them by testing them on my Knight....thanks for the link Tom it looks like I got very lucky by finding a 600c!

 

[larryderouin]

I noticed that the Knight 600 and the EICO 625 are basically identical, except the EICO uses a tube for rectification. I copied the article for personal use, and am gonna check the filiment voltage calibration as outlined. You might want to do same. My Eico is a good tester, haven't had problem 1 with it. It may be out of cal tho.

Check your voltages, and check inside for any work done on it. You may want to change the .1uf cap, and clean the Pots. At least it will give you a better reading thru clean contacts. If you can calibrate the filiment voltages, it may bring the readings of the 6au6's up. Who knows, until you do check it out.

Something to do today after I get back from MVA!

PM me with your e-mail and I'll send you what charts I have for the 625. Compare the settings of that to the 600. Test them out and see what you get on the 6AU6's. I DL'ed the charts from BAMA for the 600. I'll do same with a couple and report back in a day or so with results. Curious to see what we get.

Larry