Thoughts on valve testing!

[chriswood1900]

For many years I had not bothered with a valve tester relying on some simple voltage checks and substitution.
A few years ago having gathered a stock of old valves I needed a way of quickly weeding out the duds, so without much knowledge whilst in the US on business spotted very cheaply a simple tester made by Mercury a 990 which I discovered after some research up to be a simple serviceman’s emission tester geared to tv work.
This did prove useful as it weeded out those with OC heaters shorts and very low emissions, the problem now is I kept on wanting to know more and seeing more and more shortcomings in this basic tester.
Next stop I needed an AVO so I spotted a reasonable 2 panel tester which once I mastered the balance idea made a reasonable stab at most older valves but struggled with some of the designs of 50s/60s B9 valves.
Whilst attending RWB auction a couple of years back a smart looking CT 160 came up for sale, from my prior reading it seemed to be one of the ultimate testers so went for it, winning the auction. It turned out to have been well looked after and close to calibration which only needed a few tweaks and a clean to give me a very nice tester. I could now test almost anything I plugged in the only valves it struggled with were UL41, 6BW6 and 6550s partly because the settings given in most Avo data manuals gave settings the 160 doesn’t cover. However that was much easier once I realised that there were different settings for the CT160 given for the CV versions and a 6550 could be tested as KT88.

What are others experiences and thoughts?
Chris

[Station X]

To be quite honest I find that valve testers are only really useful for testing "pulls" where I have no set to try them in.

Most of the faults I find are open circuit heaters and inter-electrode shorts. Low emission and low gm faults are rarer and valves with these faults will often operate perfectly satisfactorily in a set.

I can generally judge a valve's condition from in circuit voltage readings although, more often than not, these indicate faulty caps or resistors. The valve tester merely confirms what I already knew.

I have a CT160, but my DMM, SG and scope see much more use.

[ms660]

The only valve tester I owned was Supreme 1-177-B, essentially a Hickok, it used a mercury vapour rectifier to supply the HT and the meter was quite durable.....

Very well built it was, it was very good for the earlier American valves, which is what I bought it for.

Second time round I'd probably go for a couple of variable PSU's instead, dual functionality and all that.

Lawrence.

[stevehertz]

I wouldn't be without my Mullard mk3 High Speed valve tester. It does what it says on the tin, pure and simple. The first thing I do with any set that I'm working on is test the valves. Knowing that you have a set of good valves in place immediately eliminates them from the equation.

[chriswood1900]

I have to own up to a bit of an addiction to test equipment, however with valve testing there is a practical aspect. I’m due to retire soon and have been building up my stocks of spares to do some of my projects, this includes buying up some valves when the price seems right. This can be at BVWS auctions, fairs and internet, in order to avoid keeping a pile of duds or on higher priced audio valves not knowing if what I buy is any good I now test them and check the results whilst I know this is not a guarantee if a valve meets its spec against the datasheet it should be a reasonable safe bet to keep.
Chris

[Phil G4SPZ]

I bought a Weston emission checker and it was a great help in weeding out the duds from my modest collection of valves. I was later lucky to be given a non-functioning Avo Mk III which I repaired, and find it invaluable.

Originally Posted by stevehertz

The first thing I do with any set that I'm working on is test the valves. Knowing that you have a set of good valves in place immediately eliminates them from the equation.

It takes but a few minutes to test the valves in a newly-acquired set and, as Steve rightly says, gives a much greater degree of confidence for forthcoming fault-finding.

[mole42uk]

The only valve tester I have is a Sussex. I gave my Mullard HSVT away after I'd built the Sussex. It does everything I need.

No, I am mistaken. I also have a two-panel AVO but I don't know if it works!

[Phil G4SPZ]

The twin-panel Avo is useful if you've got nothing else, particularly for pre-war valves, but it can be prone to oscillation when testing modern high slope valves. There are a couple of waxies inside that will need replacing if you ever decide to use it, plus a lot of exposed un-earthed metalwork. A 3-core mains lead is a worthwhile update.

[mole42uk]

Phil,
It's unlikey to get anything like mains supplied to it in the forseeable future, I don't even remember where it is!