Valve tester any advice
 

Dear Friends

I think a lot of you know about my test equipment collection, I am thinking of adding a valve tester to the collection at some point. I do intend to make use of the tester since I don't have enough valves for the substitution method when repairing vintage equipment. I have seen a few AVO valve tester on ebay recently having the Model number CT160. These are advertised at huge sums far out side my budget.

Do any of you have experience in valve tester and could advise make and models to look out for.

Regards Christian.

Re: Valve tester any advice
 

Whilst I have an AVO CT160 valve tester, I much prefer to use a Mullard High Speed Valve Tester.
Paul E

Re: Valve tester any advice
 

I also have and use a Mullard High Speed Valve Tester. They are fairly simple to use (intended for shop assistants as well as engineers) but obviously don't give as much information as the Avo testers. However if you want to know if a valve is basically OK or junk, it gives a good indication. If it indicates internal shorts, grid leakage or other nasties, but I tend to be reluctant to discard a valve that it shows as having low emission unless the spot doesn't move at all.

Re: Valve tester any advice
 

Christian,

the Mullard is a good choice for general service work, as it is quick and easy to use. It is also ideal for repetative work - when you get that box full of 2nd hand valves etc.

Another good choice for basic work is the original AVO valve tester (also known as the " two panel " tester, as it comes in two pieces). They will test most small signal and power valves that you will met in radio work - they are not good on " high slope " valves, as the tester is an older design.

The AVO valve characteristic meters (Mk1 to 4 and VCM163) are very versatile units, and will tell you a lot more than just good/bad, but they take longer to set up, and require individual adjustments for each valve (as does the tester, but it is a little easier). The CT160 also comes in to this class, but is a little easier to set up and use.

The great advantage of the AVO models is that you don't need the AVO data book - you can use any basic data book (Bernards manuals, wireless world, manufacturers data), where as the Mullard ( and the Philips tester - if you ever see one), require punch cards - no card no test.

Some of the later American testers are worth consideration (Hickock etc), but the method of setting up uses " code switches " to connect the pins to the relevant test circuits - if the valve is not in the data for the tester, it is very difficult to test it.

There are also the Taylor models (45A to C?), which look to be a poor mans AVO, though I have not used one to comment properly - if anyone has one, can they comment?

Finally, Radio Bygones produced a design for a tester recently, that may be worth alook aswell (I can dig it out if you don't have the magazine).

Jim.

Re: Valve tester any advice
 

I used to borrow the AVO valve characteristic meter from work - till the department closed down, and it was auctioned at Harpenden! A fine instrument if you have the space.

At home I now use a two panel AVO valve tester - it's old, but works well on all the valves I've thrown at it. It comes in several versions (mine is the one with the direct read-out of mA/V rather than the good/bad scale). It has the big advantage that it's tough, fairly simple, and you can easily add extra bases and modify it for testing 1.4 volt filament valves (it was designed before these were around).

Robert

Re: Valve tester any advice
 

Hickoks work well but only have sockets for US tubes: 7 & 9-pin miniature, octal, loktal, and (for older models) 4-5-6-7 pin. European tubes that don't have US equivalents won't be in the data books/roll charts. Also most Hickoks would be fairly expensive to ship. There are any number of cheaper emission testers, lighter in weight, but again, no data for non-US tubes.

Any of these can be set up for unlisted tubes, but you'd need some known-good samples for comparison. The socket switching is no more difficult than on an AVO, just different.

I was under the impression that the two-panel AVOs ran the valves with no bias.

Re: Valve tester any advice
 

Thanks for the useful advice.

I think the mullard high speed tester uses programming cards. I was put off in the past by the complication of the card reading mechanism and its reliability.Maybe I should reconsider. I will probably attend some of the radio fairs this year looking for a bargain.

Many Thanks Chris.

Re: Valve tester any advice
 

Don't think the card reading mechanism is a problem with these testers. I have repaired a couple of these testers and the main problem is normally with the capacitors. Once these are all changed the tester normally works ok. Martin Scobie at www.vintagewireless.net
Repaired my original one, as it was reasonably expensive and I did not think I was knowledgable enough to repair it! I have since repaired others myself.
Paul Stenning has also given me good advise on repairing this type of tester.
Paul E

Re: Valve tester any advice
 

Hi Gents, see my earlier thread about card exchanges for Mullard testers. I've now decided to do some tool making and make a punch to produce my own cards. Basically the manual gives most of the details to decide which of the 1-10 and A-M holes to punch.
BEWARE!!! there exists, number unknown a rogue card whic can short the transformer HT winding. A worthwhile mod is to fit fuses in each of the HT feeds from the transformer(about 10 in all) . This was a design weakness.

Ed Dinning

Re: Valve tester any advice
 

Ouch! If anyone knows the offending card number, please let us know! This could explain why some seem to suffer transformer failures.

I agree with Paul that the card reading contacts are reliable. My tester just needed a load of new caps and a couple of new valve holders on the top (the small 9 and 7 pin ones).