Low insulation puzzle: what's this?

[DPG]

Resistance decade box?

Or something related to valve testing? Maybe to set the appropriate voltage to one of the valve electrodes?

 

[HappyHippyDad]

If you show me the completed picture, then explain exactly what this machine does.... I still don't believe I would get it.

 

[Lucien Nunes]

On something else at the moment - the quest for M8 turnbuckles that are a few mm shorter than the DIN standard size. Looking at some pics online I got an idea that versions with locking nuts had shorter bodies so I ordered samples, but the bodies are the same size. The eye screws are threaded further to the end which is useful though.

I'll.put this back together after lunch and a bit of admin.

And then I will do some 026 540 310

 

[timhoward]

On something else at the moment - the quest for M8 turnbuckles that are a few mm shorter than the DIN standard size. Looking at some pics online I got an idea that versions with locking nuts had shorter bodies so I ordered samples, but the bodies are the same size. The eye screws are threaded further to the end which is useful though.

I'll.put this back together after lunch and a bit of admin.

And then I will do some 026 540 310

KT66 ?

 

[littlespark]

KT66 ?

C3PO?
R2D2?

your just spouting random letters and numbers now.. ?

 

[timhoward]

Bad picture, best I could find online.
Take it you have a vintage AVO panel tester?

 

[Lucien Nunes]

Got it. Anyone not with us, keep watching.

 

[Lucien Nunes]

VCM IV

 

[DPG]

Did I get it in post #21 then?

 

[timhoward]

Did I get it in post #21 then?

I'd say so!

 

[Lucien Nunes]

OK yes joint win, didn't see your edit, when I looked at that post it only mentioned the resistance decade box.

 

[DPG]

Thanks flip. Made my brain hurt!

 

[DPG]

OK yes joint win, didn't see your edit, when I looked at that post it only mentioned the resistance decade box.

Yes, it occurred to me afterwards. Luckily well within the edit window.

 

[DPG]

My next guess was going to be some sort of capacitance or inductance measuring bridge.

 

[Lucien Nunes]

Back in an hour or so...

 

[timhoward]

I wouldn't have got it without the valve specification clue:

KT66
026 540 310 A100V, S60V, MAV6 HTR6
It's been many years, anode, screen, ma/v, heater I think?

 

[DPG]

I wouldn't have got it without the valve specification clue:

KT66
026 540 310 A100V, S60V, MAV6 HTR6
It's been many years, anode, screen, ma/v, heater I think?

Didn't cotton on to that! Nice one

 

[Lucien Nunes]

Those settings are not for the VCM though. The 2-panel tester is a simple zero-bias tester that is not well suited to later high-gain power bottles and has to test them at low voltages. The VCM operates the valve under realistic operating conditions and can be used to plot curves. A:250, G2:250, G1: -15V. Then you are looking for Ia=65mA and gm=6.3mA/V.

Those still not with us, the rotary switch assembly I was servicing, called a 'roller switch', allows each 'test lead' of the instrument circuit to be connected to any pin of the valveholder (=socket). There were thousands of different types of valves on dozens of different types of bases, with the same pin being used for different functions on different valves. I..e for a KT66, in addition to dialling in the anode voltage as 250V, you also have to dial in that the anode is on pin 3. and the same for all the other electrodes.

Different testers had different ways of doing this but the AVO roller switch is generally considered one of the best and slickest. The settings are given in the AVO data book but if you know the valve pinout you can work them out on the fly.

For a reminder of the KT66, one of Britain's best-loved audio output bottles, see:

KT66 @ The Valve Museum

or download the dataheet here:

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwi0odDxm6HxAhXWA2MBHQGlAwwQFjAAegQIBRAF&url=https%3A%2F%2Ffrank.pocnet.net%2Fsheets%2F084%2Fk%2FKT66_GEC.pdf&usg=AOvVaw2vfZVC_ScvGOenDNbR6XBD

 

[SJD]

I wouldn't have got it without the valve specification clue: KT66

At that point, I was wondering was this some newer Kewtech MFT model I'd not heard of . . . . .

 

[telectrix]

Those settings are not for the VCM though. The 2-panel tester is a simple zero-bias tester that is not well suited to later high-gain power bottles and has to test them at low voltages. The VCM operates the valve under realistic operating conditions and can be used to plot curves. A:250, G2:250, G1: -15V. Then you are looking for Ia=65mA and gm=6.3mA/V.

Those still not with us, the rotary switch assembly I was servicing, called a 'roller switch', allows each 'test lead' of the instrument circuit to be connected to any pin of the valveholder (=socket). There were thousands of different types of valves on dozens of different types of bases, with the same pin being used for different functions on different valves. I..e for a KT66, in addition to dialling in the anode voltage as 250V, you also have to dial in that the anode is on pin 3. and the same for all the other electrodes.

Different testers had different ways of doing this but the AVO roller switch is generally considered one of the best and slickest. The settings are given in the AVO data book but if you know the valve pinout you can work them out on the fly.

For a reminder of the KT66, one of Britain's best-loved audio output bottles, see:

KT66 @ The Valve Museum

or download the dataheet here:

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwi0odDxm6HxAhXWA2MBHQGlAwwQFjAAegQIBRAF&url=https%3A%2F%2Ffrank.pocnet.net%2Fsheets%2F084%2Fk%2FKT66_GEC.pdf&usg=AOvVaw2vfZVC_ScvGOenDNbR6XBD

I'm convinced now. yous was born on Mars and come here to confuse us all into abject surrender.