[JTbbb]

Don't mess with it if it is working.

Tube tests as NOS and sounds wonderful. I wondered whether it might stabilise the crack? But I may take on board what you suggest.

I bought a tube last year that had a loose base and used a medium cyno, which has worked perfectly. Mind you, that tube didn’t cost me much, so if it had gone horribly wrong, it wouldn’t have mattered.

 

[bcowen]

Don't mess with it if it is working.

I agree. As long as the base is still tight to the glass, there's more risk in making it worse.

 

[TLO]

Hello all,

I’m thinking of squeezing some Epoxy Resin, with a small flat blade screwdriver, into what looks like a huge crack! But actually isn’t. The crack doesn’t extend to the bottom, and the base is tight to the glass. Any other suggestions?

If it really bothers you, use heat tube. The fun part is there are many colors to choose from...
For loose base, I always use the nail remover method, epoxy or glue is too messy and ugly.

 

[JTbbb]

If it really bothers you, use heat tube. The fun part is there are many colors to choose from...
For loose base, I always use the nail remover method, epoxy or glue is too messy and ugly.

What is the nail remover method?

 

[TLO]

What is the nail remover method?

Drip a small amount of nail polish remover along the small gap between the base and glass, rotate the tube as you go, clean the excess then leave it standing upright overnight for it to dry or use a heat gun / blower to speed up the process. This method will only work well if the tube has not lost its cement compound.

 

[TLO]

Before applying the remover, always wrap a small piece of cloth around the base tightly to protect the precious print. Most of the time, I dont really wipe the excess but blow the remover dry with my mouth. You dont want to damage the print and lose a couple of hundred dollars there...

 

[DenverW]

Hello all,

I’m thinking of squeezing some Epoxy Resin, with a small flat blade screwdriver, into what looks like a huge crack! But actually isn’t. The crack doesn’t extend to the bottom, and the base is tight to the glass. Any other suggestions?

Leave it, treat the tube gently.

 

[ostewart]

This turned up from eBay (£11.19 in an auction) - I don't have readings but I reflowed solder to the pins as the black base is quite loose (seems it's not solder that's the issue, and actually epoxy, oh well) and cleaned up the pins (after I took these photos - pins showing flux residue and excess solder that has been filed down).

A 4 - guessing January 1944

I'll grab some clear nail varnish for the base.

Works fine in my Xduoo TA-26

 

[paradoxper]

Not sure where I bought these. Which means slow down. And that is no fun.

I'll run these in 1578 quad against the CFA Hybrid.

 

[ChrisPDX]

Another tube noob question here ... I'm pending payment on a pair of VT-231 / CAA tubes but the seller is only providing one type of measurement ( 2600 / 2700 and 2700 / 2700 ). Those measurements -- I'm afraid I don't know what is being measured nor the units -- seem good, but there are no "ma" measurements (typical range seems to be ~6.0). The seller has a good reputation. Would you feel confident proceeding without the ma measurement? I know there are so many factors and measurements may not be accurate for various reasons. Thanks for any advice or guidance.

 

[u2u2]

Buy the seller, not the tubes. You are satisfied he has a good rep so I would say go ahead.
Enjoy them when they arrive.
Problems? He will help if his rep is genuine.
That has been my experience so far...

 

[bcowen]

Another tube noob question here ... I'm pending payment on a pair of VT-231 / CAA tubes but the seller is only providing one type of measurement ( 2600 / 2700 and 2700 / 2700 ). Those measurements -- I'm afraid I don't know what it being measured nor the units -- seem good, but there are no "ma" measurements (typical range seems to be ~6.0). The seller has a good reputation. Would you feel confident proceeding without the ma measurement? I know there are so many factors and measurements may not be accurate for various reasons. Thanks for any advice or guidance.

The seller is providing GM (transconductance) measurements which are as good a measure as mA/V for small signal tubes like 6SN7's. The generally accepted "bogey" (or average NOS) value for a 6SN7 is 2600, so both triodes in both tubes are measuring at or slightly above average NOS. This is assuming his tester is calibrated which there's no way of knowing for sure.

 

[David222]

Another tube noob question here ... I'm pending payment on a pair of VT-231 / CAA tubes but the seller is only providing one type of measurement ( 2600 / 2700 and 2700 / 2700 ). Those measurements -- I'm afraid I don't know what it being measured nor the units -- seem good, but there are no "ma" measurements (typical range seems to be ~6.0). The seller has a good reputation. Would you feel confident proceeding without the ma measurement? I know there are so many factors and measurements may not be accurate for various reasons. Thanks for any advice or guidance.

There are two triodes...he is giving you a measurement for each (which is what he should do). The "NOS" spec for 6SN7 is 2600 (if not mistaken).... so he is showing you with data that your tubes are in fact NOS.

--> What you want to look for is what type of machine is he using to measure...many ebay dudes have varying machines and if they are not calibrated then the measurements are worth jack... consider looking for an AT1000 as it provides reliable results (IMHO).

 

[cddc]

There are two triodes...he is giving you a measurement for each (which is what he should do). The "NOS" spec for 6SN7 is 2600 (if not mistaken).... so he is showing you with data that your tubes are in fact NOS.

--> What you want to look for is what type of machine is he using to measure...many ebay dudes have varying machines and if they are not calibrated then the measurements are worth jack... you are best looking for an AT1000 as it provides most reliable results (IMHO).

I used to think Amplitrex AT1000 is a great tester, but after reading all the negative reports on the numerous errors in its software and the factor that Amplitrex has NEVER issued any firmware update to correct the reported errors, I have lost my confidence in Amplitrex test results.

For example, the Amplitrex will overstate the 6AS7G and 6080 tubes. Amplitrex claims to use tube datasheet specs to test tubes, so 100% new 6AS7G and 6080 tubes should has a Mutual Conductance of 7000 uMhos according to the RCA 6080/6AS7G datasheets, but Amplitrex incorrectly uses the minimum Mutual Conductance value 5800 uMhos on the RCA datasheets as its 100% new standard to judge 6AS7G / 6080 tubes. Now, a mediocre 5800 uMhos 6AS7G / 6080 tube will be claimed as 100% new when tested on Amplitrex, while in fact it’s merely a used 83% (5800/7000 = 83%) tube, a 17% overstatement from Amplitrex.


There are many other errors reported by users, so I really don’t know if I can trust the Amplitrex test reports. The most terrible thing is that Amplitrex has never issued any firmware update to address the numerous reported errors. My guess is that the programmer who wrote the initial firmware for Amplitrex tester has long left Amplitrex, and Amplitrex just couldn’t or is unwilling to find a capable programmer to update or rewrite the firmware.

Another thing I don’t really like about those computerized testers (like Amplitrex) is that all things are hiding in the codes, it’s like a black box to users, users can never figure out what tube testing parameters are used by the codes and whether they are correct (obviously they’re not always correct, just like the numerous errors reported by Amplitrex users).

 

[JTbbb]

The seller is providing GM (transconductance) measurements which are as good a measure as mA/V for small signal tubes like 6SN7's. The generally accepted "bogey" (or average NOS) value for a 6SN7 is 2600, so both triodes in both tubes are measuring at or slightly above average NOS. This is assuming his tester is calibrated which there's no way of knowing for sure.

This tube testing business can be a real conundrum, can’t it. I’ve just had 9 6sn7gt type tubes, all from the ‘40s, tested by a professional on a calibrated tester. The NOS figures below are what you folk’s would expect from this machine? Out of the 9 tubes I have 4 that are pretty much at or slightly above NOS and the remaining just below.

Valve test data for 6SN7 X9 18/02/2022

Valve tester AVO VCM 163

Test parameters for type 6SN7
Heater, 6 Volts
Plate, 250Volts
Control Grid, 8Volts Negative

Good/New 6SN7, 9 MA 2.9 MA/V