[Oskari]

Quote:

Found the net for information on the date code of British tubes:
. . .
Whether it is correct information?

 
This was the CV date code until they switched to numbers. The second letter indicates the month: A = Jan, etc. Apparently MOV used this for their non-CV production as well.
 

1. http://www.vmarsmanuals.co.uk/newsletter_articles/cv_valves.pdf
2. http://www.tubecollector.org/cv-valves.htm

 

[rosgr63]

Hello Oskari,
 
Thanks for the valuable info, nice to hear from you.
 
You always have a very informative answer when I am struggling with these MOV tubes.
 
Edit:MOV

 

[StalkerAssassin]

This was the CV date code until they switched to numbers. The second letter indicates the month: A = Jan, etc. Apparently MOV used this for their non-CV production as well.

• http://www.vmarsmanuals.co.uk/newsletter_articles/cv_valves.pdf
• http://www.tubecollector.org/cv-valves.htm

Cool, thank you very much for the information.

 

[Mr.Sneis]

Sylvania green labeled 6sn7 gta - 3 holes in plates, parallel plates, splash of chrome on the top of the glass.  That is not the same as a "bad boy" right?  I like the 3-hole parallel plate GTA more than the offset plate version of the 6sn7 gta.  I now have 4 of them!

 

[StalkerAssassin]

Sylvania green labeled 6sn7 gta - 3 holes in plates, parallel plates, splash of chrome on the top of the glass.  That is not the same as a "bad boy" right?

Yes, it's a different tube.

 

[Solude]

Arg my Ken Rad came in and shipping did what shipping does... claimed another NOS tube  Tested for noise and balance before shipping, arrived noisy and way out of balance.
 
I'll burn it in tonight but don't expect miracles.

 

[rosgr63]

Sorry to hear this but I don't think shipping could make the sections go out of balance.
It can cause shorts/ leakages but would not make the sections go out of balance.

 

[Solude]

No change after a night of burn in.  Sigh, oh well.  It was his only phono grade Ken Rad so no replacement either.  That said, since the PWD2 has warmed up, I've come to love the Bad Boy again so meh.  
 
Would also add, this Ken Rad is super bright.  You can hear the added bottom, but it has even more added top.   Like a super V EQ.  Not listenable even at modest volume.

 

[Mr.Sneis]

Odd story.  I have an old Cossor 6sl7gt tube that tested fine on my local shop's Seco 1100 and when I used it in 3 different amps it had the same problem where one channel would get very very noisy after a little use.  I just about threw this tube away but sometimes tapping the tube would help bring it back of course it would then come back shortly thereafter.  Recently I picked up a "socket saver" and noticing that its gripping force was extremely tight, I tried it with the old Cossor.  Fingers crossed but so far it seems to be working fine, I guess the real test will be leaving it on for 5 or 6 hours to see.

 

[Solude]

That's what my guy said as well..
 
Try tapping the tube firmly on a table top, and snapping the glass with your fingernail.  The trick is to knock any possible cathode material that may be caught in the grid, to the bottom of the tube.

 

[Mr.Sneis]

Quote:

That's what my guy said as well..
 
Try tapping the tube firmly on a table top, and snapping the glass with your fingernail.  The trick is to knock any possible cathode material that may be caught in the grid, to the bottom of the tube.

 
The past few weeks I have learned that just because a tube tests good doesn't mean all that much without having actually auditioned the tube for an extended period of time.  I have maybe 3 or 4 of these tubes that test in the good range on the Seco but I never use them because of stupid issues that pop up in use.  I figure I'd rather prefer to purchase from a seller who states something along the lines of having used the tube and it worked flawlessly rather than some guy with a tester saying his tube tests good!  I'm still a tube n00b though.

 

[rosgr63]

Quote:

That's what my guy said as well..
 
Try tapping the tube firmly on a table top, and snapping the glass with your fingernail.  The trick is to knock any possible cathode material that may be caught in the grid, to the bottom of the tube.

 
Loose material during transit can cause problems, even shorts and leakages so tapping the tube might cure the problem.
 
I usually amp test newly acquired tubes for a couple of hours to make sure there are no noise or other issues.

 

[dminches]

Quote:

 
The past few weeks I have learned that just because a tube tests good doesn't mean all that much without having actually auditioned the tube for an extended period of time.  I have maybe 3 or 4 of these tubes that test in the good range on the Seco but I never use them because of stupid issues that pop up in use.  I figure I'd rather prefer to purchase from a seller who states something along the lines of having used the tube and it worked flawlessly rather than some guy with a tester saying his tube tests good!  I'm still a tube n00b though.

 
Bob Putnak, the guru of tubes and testers has said this to me time and time again.  Testing information is just one data point.  It doesn't mean everything by a long shot.

 

[Skylab]

The main purpose of using a tube tester for me is to eliminate tubes that are for sure bad before sticking them in an amp where REALLY bad things could happen.

 

[Solude]

To be fair, noise testing from my seller is done in a phono pre-amp out to speakers, ie super high gain to spot light any noise.