Valve testing. Help for beginners.

[Collectabug]

My husband and I have become the owners of a vast number of valves, of all sorts, types and ages. We want to sell them but realise that ideally
we need to test them and this is our problem. We have been looking for a cost effective solution and understand that instruments can be bought to test them, that they are capable of testing different valves by using different settings and sockets to accept the valves.

On having a look around we have found several Avo 2 Panel Testers that are in our budget (around £200) but are confused as they superficially seem the same but on closer inspection the sockets seem to have been configured differently, as though they were customised. Is this a possibility, as it seems to us the internal wiring would need to be routed to accept the valve that the socket has been configured for, thus making the operation of each of them entirely unique. We've also seen ones that have a 'heater' switch, but in different locations, and some don't have one at all.

Of course we may be misunderstanding how these work and could really use some advice. We really need to be able to test as many varieties as possible so is there anything we should be looking out for? Any advice would be very helpful and we would be most grateful.

Firstly, test the filament for continuity, With a tester on Ohms, must read 0 (continuity) To know which of the valve pins are the filament, you can look for the valve characteristics on Internet or in a Valve book that there are many arround.

The valves that has continuity on the filament pins are ok for the next test on the valve tester to see the life left.

The valves that not show continuity are faulty, only for display.

I hope this will be useful for you.

Aitor Eneko

[GrimJosef]

Originally Posted by Collectabug

... but on closer inspection the sockets seem to have been configured differently, as though they were customised. Is this a possibility, as it seems to us the internal wiring would need to be routed to accept the valve that the socket has been configured for, thus making the operation of each of them entirely unique ...

Of course we may be misunderstanding how these work ...

I think you are misunderstanding how these work. Each socket has not been configured for just one type of valve. If you consider the IO octal socket, for example, both the KT66 valve and the 6SN7 valve fit this socket. But these two valves are entirely different, both in the actual type of valve (KT66 is a beam tetrode, 6SN7 is a double triode) and, not surprisingly therefore, in the pin connections.

Each and every socket is actually configured using the bank of rotary numbered switches for the particular valve you want to test.

I should say also that while it is tempting to consider testing valves, it's often not economically justified. It's time-consuming and beyond a basic working/not working result it may not add much to many valves' value (although for some more expensive types it might). If you are just testing radio valves, rather than high-end audio ones, I think you would struggle to make the minimum wage when you consider the time you spend versus the economic value that you add.

Cheers,

GJ

[60 oldjohn]

What valves are there? Some are virtually worthless, while PX4, PX25 and a few other working valves are worth £100's testing these on the wrong voltage could burn out the filament making them worthless. I think you need someone you can trust to advise you, or look on the sold section of Ebay, bear in mind asking price and what they are actually sold for can be very different. Also repair men used to put the used valve back in a new pack (just in case valve had a little life left) A basic test would be with a Multi meter cheapest one you can find set to ohms, sometimes with a buzzer, to check for a circuit between two and sometimes three pins.

John.

[Radio Wrangler]

All the valve testers you'll come across for sale are now 50+ years old and are likely to need some restoration work to get them going. They are a hobby in their own right. The later models were somewhat improved, but a glance at selling prices will scare you. Those of us on here with testers got them before the prices went silly. Believe it or not, these things once were treated as scrap.

A second problem is that valve testers are fragile and can be damaged by inappropriate settings of their controls. The parts damaged are pretty much unobtainable. So if you do get one, you'll need showing how to use it.

The first step is to go through the valves you have. Build a list of types. Use a simple, cheap multimeter on its Ohms range to check the valve's heater filament, getting pin assignments from the internet or a valve data book. Any open circuit heaters shows that a valve is useless. This weeds out the obvious duds and saves you wasting time on testing them seriously.

Some valve types, mostly ones developed for TVs are worth little. General purpose valves are worth a bit more, but it's the demand from audio aficionados that have driven up the prices of their favourite types.

Repairers as said before, took a new valve out of its cardboard box, fitted it to the set, and shoved the replacement one into the cardboard box to protect it from breakage. So there are boxes and boxes of part-worn valves kicking around. The boxes look new, the valves rarely show use visibly.

Start with a list and we'll tell you which are worthy of attention.

David

[Diabolical Artificer]

"Start with a list and we'll tell you which are worthy of attention." That's a good idea, but broadly speaking the common valves which fetch the most money use only two types of bases, EG octal and B9A, so a simple meter like this one would do at first - https://orangeamps.com/products/acce.../valve-tester/ it's easy to use in comparison with a "proper" valve tester.

Sort the valves into the various types first P types, any valve starting with the letter P, EG, PL84, PCC84 etc, these are TV valves, and in the main not worth much. U types, used in AC sets etc, Eg UL84 etc are also of a lesser value.

The ones your after from a monetary POV are any valve starting with ECC, EG ECC81, 82, 83, the latter being worth more than the former. these double triodes have another designation - 12, EG 12AT7, 12AU7 and 12AX7, the last being an ECC83, and lastly EL84, all these "E" types have 9 pins, IE B9A base. Other valves to look for are EL34 and EL84, KT66 and 88, these have an octal base or 8 pins and are bigger in size, two other octal valves to put on the "good" pile are the 6SN7 and 6SL7, both octal.

Another way to sort them is by size, older valves will be bigger and have less pins on the whole, usually four or five, two to definitely put on the "good" pile are the PX4 and PX25 as mentioned previously, these can't be tested on the simple tester above, but there's a chance there is someone off the forum local to you who will help testing them.

It's a lot more complex than stated above, there being 1000's of other types of valves. Here's one good site to look up valves - http://www.r-type.org/search.php

Andy.

[Craig Sawyers]

Agree with the small value of radio and TV valves. A quick search showed that last job lot that went on eBay, item 323702708043, was 168 NOS radio/TV valves and went for £51, or 30p each.

Audio ones, depending on brand, age, shape of getter (yadda yadda) can go for tens to hundreds of quid each if NOS.

But the first thing is to sort them as Andy has said. Radio/TV ones sell as a job lot with zero testing, then make an inventory of audio ones and post it here and we can advise further.

Craig

[John M0GLN]

Originally Posted by Diabolical Artificer

Sort the valves into the various types first P types, any valve starting with the letter P, EG, PL84, PCC84 etc, these are TV valves, and in the main not worth much

Except as '60 oldjohn' says in post #4, some P types are very valuable.

John

[Simon Gittins]

The Avo 2 Panel Testers are the oldest of the AVO valve testers and were first made in the late 1930s.

The main differences are in the valve panels themselves. The first testers were sold with two of these, one for USA valves and one for UK valves; this is the less useful version today.

Later 2 Panel Testers had a single valve panel with a roller switch to set the connections as required and allowed testing of a greater range of types.

The heater switch is only needed if testing 1.4 volts battery valves (these are not particularly valuable).

[ajs37]

a working Mullard HSVT machine may be the easiest option for you - they don't appear very often, but they are normally sub £100 (make sure they have the card boxes!)
Cheers
Andy

[GMB]

but they are normally sub £100

A restored and working one will be way more than that these days!

[snowman_al]

One thing no one has mentioned yet and is the place to start is to categorise them into their various valve base types.
Common are B4, B5, B7, Octal, B9A, B7G, etc., but there are dozens more.
Then make a list of each B4 type, B5 type... Octal type etc. etc. Then you can sub categorise into voltages and or letter types, makes etc.

You will waste your money buying a valve tester, one it is a long and tedious task and pointless testing low value valves. Second unless you know what you are doing you can easily damage good valves... The AVO you mention is a museum piece and pre dates several of the more interesting (expensive) valve types and bases.

Best to test for heater or filament continuity as a start. Then weed out any that have gone white inside.

I guess we are all waiting to know what 'a vast amount' is and what gems are in there?

Good luck, Alan

[GrimJosef]

Originally Posted by Simon Gittins

The Avo 2 Panel Testers ...

The main differences are in the valve panels themselves. The first testers were sold with two of these, one for USA valves and one for UK valves; this is the less useful version today.

Later 2 Panel Testers had a single valve panel with a roller switch to set the connections as required ...

Ah. I wasn't aware of the earlier panels. I can see that they would have very limited usefulness. My comment above (post #3) only related to the version with the roller switches.

Cheers,

GJ

[Collectabug]

Thank you all so very much for your time and input. We already appreciated that we were dabbling in a 'dark art' but didn't realise the complexity of what we were dealing with. We are going to spend some time absorbing everything that you've told us and see what we have. We estimate that we have over a thousand of them so it's going to take a while!

Many thanks again. Sharon

[paulsherwin]

It may be worth your while contacting a few valve dealers and asking if they are interested in buying them all as a job lot, untested. You will get a lot less than by testing them all with a tester and selling them individually on eBay, but that involves a great deal of work. Just testing them properly will take several minutes per valve, it's not like testing a light bulb.

As others have said, buying a fully restored and working valve tester is also a major expenditure.

[GrimJosef]

I suppose it goes without saying though that a good tester might not lose much value in, say, 6 months. Depending on where you buy it from (mostly whether you lose much in auction premiums) you might re-sell it when you're done for close to what you paid for it.

EDIT: If you get good at it you could even charge other people to test their valves .

Cheers,

GJ

[Half a Mullard]

Could you post a few photos of a selection of the valves? It could help to give an idea of what you have.

[Herald1360]

It's worth asking......

Did you also acquire any other "stuff" with the valves? Things like old valve amplifiers and even some components may be worth more than you might think.

[CambridgeWorks]

You don't say whether they are lose or boxed. If boxed, does the paper or cardboard wrap within look untouched or well used. Do any boxes have numbers crossed out and different ones written in place.
Rob

[Collectabug]

Just a quick note to reply to the questions, it does look like there are some other items in with them, I'll report back if I find anything that seems related. In regard to the question about whether they are loose or boxed - there are ones that are clearly used and unboxed, ones that appear completely unused and in a pristine box and just about everything inbetween.
As there is so many I'm going to take a random selection and have a look through and sort them out, I'll be back!
Sharon