How to use this valve tester?

[analogadikt]

Greetings to all,

This is my first post in this section, although I have a few posts in the vintage audio section.
I have been using valve amps for the past few years, overhauled a few. The usual recap and checking voltages type of jobs.
I have no previous experience of using a valve tester, in fact, this one is the first that I have actually seen and touched in my life, so I need an in depth tutorial about how to go about using it. I hope the good folks here won't mind that.
So I download the datasheet of the valve to be tested, and plugthe specimen in the correct socket. The confusion starts after this. I suppose that now I have to match the pin numbers in the thumb wheel switch to the function marked on top of that. But the markings on this machine and what is written in the datasheet (for example, EL84 pinout) does not match. H+ and H- would be heaters, C is cathode? and A1 /A2 are anodes? G1 could be grid, but where is the second grid connection? And are S, D1 and D2?

Regards,

[Cobaltblue]

Hi it would possibly help to know what kind of valve tester this is apologies if it's hidden in the text somewhere.

Cheers

Mike T

[Electronpusher0]

Hello,
what model valve testerdo you have?
If it is an AVO one then all the information you need is in the AVO book. See attached.
Basically you look up the valve number you are going to test and the tester settings are all there along the line.
If you do not have the instructions for your tester do try and get them and read them before attempting any testing.

Peter

[analogadikt]

Sorry, the images did not attach to the previous post. Here they are.

Regards

[Radio Wrangler]

Knowing and admitting to yourself that you don't know how to use it is a very good starting point. A number of people have bought them and tried to find out how to use them by experimentation. The drawback to this method is that most valve testers can be damaged quite easily by nothing more than using inappropriate settings of their controls. Some parts inside some of the best valve testers are irreplaceable. It's rather distressing to hear of rather nice instruments suffering avoidable damage.

So, as Mike says, the next step is to say which make/model you have so that someone with experience of that sort can provide guidance.

Remember that valve testers are just that, they aren't burn-in rigs and their components are sized only for brief operation. Some people have tried to use them for hours long running and have burned out transformers etc.

Remember also that you don't really need a valve tester. The best arbiter of whether a valve is good or not is how it operates (voltages, currents, gain) in its intended circuit.

Valve testers are good for screening stocks of valves to weed out the bad ones. They weren't much used in repair shops, but often the front shop would have one for testing customer's valves.

David

[analogadikt]

Thank you for the responses.

I am a hi-fi and vintage equipment enthusiast. I have dozens of valve amps, and boxes of valves, most of them rescued from the flea markets of Mumbai (erstwhile Bombay). I and another friend had to teach oursalves to repair these old amps, as technicians from back in the day are no longer available. The repair guys of today do sub assembly level repairs of cheap CD players and flat screen TVs, nothing else.
The valve tester is Indian made. The manufacturer is still around, but I doubt they have any information on something that was made fifty years ago. Am uploading more pics as we go along.

Regards,

[analogadikt]

Last set of pics.

[ms660]

It might be based on the Avo VCM MK111? (so far as I can make out all the correct controls for the settings etc seem to be there) If so there's no shortage of Avo valve data and instructions, eg:

https://frank.pocnet.net/instruments/AVO/index.html

6th photo for the Avo MK111 front panel:

https://antiqueradios.com/forums/viewtopic.php?t=93437

Front panel etc photo's also here:

https://www.radiomuseum.org/r/avo_va..._mk3_mk_3.html

Lawrence.

[retailer]

As ms660 says it certainly looks like it's a copy of an Avo MKIII, but as others have warned it can be damaged by incorrect use - it seems you don't have a user manual as you say you downloaded a data sheet for an EL84 you are trying to test, if I was doing this I'd get a copy of the Avo MKIII user manual read the test procedure and do a few trial runs with no valve plugged in to familiarise myself with the process, and try to understand what is actually happening, it will help you - from personal experience I've learnt that while you have your head down reading the manual for the next step the meter needle may be wrapping itself around the end stop.
Once familiar with the process, try an actual test - S is probably G2 or screen - start with a low current valve, a pentode preamp of some sort - and double check the Avo data book switch settings will work before plugging in the valve - measure voltages (cathode to anode, screen etc) at the valve socket - if it checks out then proceed with a known good valve and keep your spare hand on the power switch, just in case. If luck is with you it will all work out, if you are unwilling to take the chance that your tester is an Avo copy then a you'll need to track down the correct user manual - good luck.

Nicely made bit of kit!

[analogadikt]

Thanks for the tips, suggestions and remarks. Have downloaded the AVO mk III. Manual. The Indian manufacturer is still around, I shall check if they have anything.
https://www.aplab.com/libaray-litera...atalogues.html

Regards,

[Radio Wrangler]

Whatever circuit it uses, the quality of construction is excellent. A beautiful bit of kit.

The panel meter looks American. Simpson or Triplett maybe?

David

[knobtwiddler]

Others have beaten me to it. That thing is an advertisement for Indian-made electronics!

[analogadikt]

Originally Posted by Radio Wrangler

Whatever circuit it uses, the quality of construction is excellent. A beautiful bit of kit.

The panel meter looks American. Simpson or Triplett maybe?

David

Bingo! It is a Simpson meter.

Looking at the carrying case type construction and military green case, I am now suspecting that this could have been made for the defense department. It would not have been cheap when new, and small private businesses could have hardly afforded it.

Regards,

[Craig Sawyers]

The build quality is excellent. Cable loom lacing is very good to see. That is a very nice instrument.

It does indeed seem to be similar to an AVO II or III. The only noticeable difference is that the anode and screen voltage switches don't have as many settings as the AVO's.

Craig

[David Simpson]

Namastey Anwesh,
Shukria for posting this very interesting thread on your valve tester. Certainly a well made piece of test equipment. And the Applied Electronics catalogue is full of very interesting items.
Keep us informed of your progress, Kripaya.

Khudha Haffis, David

[analogadikt]

Originally Posted by David Simpson

Namastey Anwesh,

Khudha Haffis, David

Thank you Davidbhai,

[David Simpson]

Hello again Anwesh, hopefully the AVO VCM MK3 Workshop Manual you have downloaded will prove to show a close relationship to your VCM. If you cannot source an AVO Valve Data Manual(which gives the thumbwheel switch code settings for thousands of valves, plus the required testing voltages, etc.), I have a spare hardback copy you can have for just the postage cost. Just PM me your address.
This forum site has a healthy band of Valve Testing & Valve Tester Collecting enthusiasts. The general concenus over the years is that VCM's & Valve Testers are approaching pensionable age & need lots of careful use & maintainance. Damage to sensitive meters, the Th./Wheel switch, or the multi-secondary mains transformer could cost a Lakh of Rupees. As RW(David) says - they're not for "burning-in" or "soak testing" valves, particularly the likes of KT66's or KT88's or other powerful Beam Tetrodes or Pentodes, or the current trend for using pre-WW2 big Triodes such as PX25's in retro-amps.
Also note - just about all of the commonly used valve testers, and particularly AVO's range(therefore I suspect yours aswell), test valves with mains AC(50Hz in the UK) Sinewave sourced voltage pulses on the Anode, Screen, Grid - NOT DC. Consequently the circuit diagrams can be arkward to understand by the un-initiated. If you've acquired a DC working VCM - then you're the luckiest guy in all India !

Regards, David

[analogadikt]

Originally Posted by David Simpson

Hello again Anwesh, Also note - just about all of the commonly used valve testers, and particularly AVO's range(therefore I suspect yours aswell), test valves with mains AC(50Hz in the UK) Sinewave sourced voltage pulses on the Anode, Screen, Grid - NOT DC. Consequently the circuit diagrams can be arkward to understand by the un-initiated. If you've acquired a DC working VCM - then you're the luckiest guy in all India !

Regards, David

There is a ss rectifier board in there, it has 3 diodes and a few resisters which could droppers. The diodes are BEL (what else) BY126, 127 while I cannot make out the third one.

Is there a rectifier board in all AC VCM?

Regards,

[Radio Wrangler]

The valve testing circuits may be AC, but the meter movement is DC, so there has to be rectification of some form to suit the meter. Sometimes the valve under test does the job, but some DC is needed as well.

David