Low insulation puzzle: what's this?

Lucien Nunes · Jun 18, 2021

Damp here this morning, and the insulation resistance on a piece of workshop equipment seemed a bit low. I could influence the reading by pressing my hands against the outside of one of its controls. That, and the fact it is getting a bit stiff to operate, show that it's time for this control to be stripped down and cleaned. Metal deposits and dirt build up inside over the years and cause leakage.

The main core of the thing consists of 36 parts threaded onto a shaft. I slide them onto a long screwdriver to preserve their order and orientation as I take them off. Then as I clean each one I put it back onto the shaft.

What equipment is it part of? The maker's name will be familiar but the equipment itself probably not so much. A couple of people here will get it in one. Give the others a chance.

DPG · Jun 18, 2021

When you said about the items on the shaft I was thinking some sort of cam operated programmer. But the photo doesn't show one.

Lucien Nunes · Jun 18, 2021

Definite similarities though. That pic shows some of the conductive build-up on a moving part. It rotates around this part:

DPG · Jun 18, 2021

Some sort of slip ring then? A rotating table?

Lucien Nunes · Jun 18, 2021

Nine sliprings, if you want to call them that.

DPG · Jun 18, 2021

So transferring power to a rotating part. Nine rings to cope with the amount of current needed to be transferred?

Lucien Nunes · Jun 18, 2021

Nine because there are nine separately movable subassemblies. Hub, fixed contact (slipring), rotor and moving contact.

DPG · Jun 18, 2021

Tricky. Is it a machine tool of some sort, or some obscure test rig?

Lucien Nunes · Jun 18, 2021

Measuring instrument. Hurry up, I'm on section 8 of 9

littlespark · Jun 18, 2021

Is it the Enigma Machine??

Lucien Nunes · Jun 18, 2021

Also lots of similarities.
Section 9's wheel and moving contact cleaned

DPG · Jun 18, 2021

Struggling. If nobody guesses can we have another clue?

Lucien Nunes · Jun 18, 2021

Inserting the contact rods.

DPG · Jun 18, 2021

Still looks like a cam programmer to me.

littlespark · Jun 18, 2021

Some form of calculating machine.

Lucien Nunes · Jun 18, 2021

Operated manually. Nine 1-pole 10-way switches in a matrix. Dial each of the nine wheels to a setting from 0-9.

Bear in mind that it is a piece of equipment that I actually need to use. I don't have a substitute. And that insulation resistance is important.

littlespark · Jun 18, 2021

So thats how lucien types up his threads?

Lucien Nunes · Jun 18, 2021

I did make a ZX81 input device consisting of three dials and two buttons, when my membrane keyboard gave out in the middle of a project.

Lucien Nunes · Jun 18, 2021

Detent springs adjusted and shaft nuts locked with lacquer

timhoward · Jun 18, 2021

Lucien Nunes said:
I did make a ZX81 input device consisting of three dials and two buttons, when my membrane keyboard gave out in the middle of a project.

The ZX81 keyboard wasn't the finest piece of engineering ever! Had that ribbon cable in and out many times....

DPG · Jun 18, 2021

Resistance decade box?

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

HappyHippyDad · Jun 18, 2021

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 · Jun 18, 2021

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 · Jun 18, 2021

Lucien Nunes said:
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 · Jun 18, 2021

timhoward said:
KT66 ?

C3PO?
R2D2?

your just spouting random letters and numbers now.. ?

timhoward · Jun 18, 2021

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

Lucien Nunes · Jun 18, 2021

Got it. Anyone not with us, keep watching.

Lucien Nunes · Jun 18, 2021

VCM IV

DPG · Jun 18, 2021

Did I get it in post #21 then?

timhoward · Jun 18, 2021

DPG said:
Did I get it in post #21 then?

I'd say so!

Lucien Nunes · Jun 18, 2021

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

DPG · Jun 18, 2021

Thanks flip. Made my brain hurt!

DPG · Jun 18, 2021

Lucien Nunes said:
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 · Jun 18, 2021

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

Lucien Nunes · Jun 18, 2021

Back in an hour or so...

timhoward · Jun 18, 2021

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 · Jun 18, 2021

timhoward said:
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 · Jun 18, 2021

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 · Jun 18, 2021

timhoward said:
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 · Jun 18, 2021

Lucien Nunes said:
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.

Lucien Nunes

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