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Old 7th Apr 2005, 8:01 pm   #1
PaulR
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Default Buying a Valve Tester

I am toying with treating myself to a valve tester. They go for widely differing prices on Ebay with the AVO seeming to get the best prices. Recently a Taylor 45C went for £117 which is a bit more affordable A bewildering variety of them apprears on Ebay.

My questions are:

a) Are any of them worth buying other than the very expensive AVOs? I mean are they any use and do they test a large range of valves. I realise they are probably not cost effective as you could test a lot of valves by substitution, even for the price of the cheaper ones.

b) Another that turns up fairly regularly is the Mullard High Speed. Presumably this needs a specific card for each valve. Most seem to have getting on for 300 cards. How is this used and am I fairly likely to get all the cards for the more common 1950s radio valves? Are the cards available?

c) Are they fairly reliable? I imagine they are difficult to impossible to repair if they go wrong.

d) Is it just a daft idea to buy one

Thanks once again

Paul
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Old 7th Apr 2005, 10:02 pm   #2
Paul Stenning
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Default Re: Buying a Valve Tester

Some people are critical of the Mullard High Speed tester, but I rather like mine. Obviously it is not as comprehensive as the AVO, but then the AVO is a "Characteristic meter" which is not really the same as a "tester".

The Mullard is a go/no-go tester. It does not give any figures, so it is no use for matching pairs of audio output valves for example. You simply see where the spot on the CRT is for each test, and if it's below the threshold the valve is in need of replacement. I find the thresholds tend towards replacing valves that are servicable, and although some suggest it's a ploy by the manufacturers to sell more valves, I think it is just them being realistic and setting the limit at something like three months regular use.

Valves that are a bit below the threshold on emission I tend to keep and label as such, whereas ones where the spot hardly moves get discarded. Tests for grid current and internal shorts etc are more definitive, and such valves get discarded. You get a feel for what's probably OK and what is hopeless with a bit of use.

There should be two boxes of cards with the tester. Each card has a number, so you need the cross-reference charts to look up the card to use for a specific valve. Some valves have two to four cards - this is generally multi-part valves. My index goes up to around 1100, however several were never issued and some sets seem to be missing some of the earlier ones. Mine has all the more recent ones I need, apart from one, and I got someone to send me a photocopy of this and made one from thin plastic from a model shop.

There should also be three cards labeled "mains", "HT" and "reject" which are used for setting the unit up.

Operation is very straightforward, and is exlained in the manual and on the frst page of the cross-reference charts. it only takes a couple of minutes including looking up the card to use and doing the job (a bit longer for multi-card valves). The quick operation makes it a good choice for working through a load of untested valves, and it's quick enough to make it worth testing all the valves in a set you are repairing. Even if you don't use it that often, there isn't much to remember. If the chart and/or instructions are missing, they are on my Valve Data CD-ROM

As for reliability, the only problem I had with mine was leaky caps. They had been replaced in the past with metal cased ones, but I needed to replace them all again. I used the yellow 1000V polyprop types.

The spring contacts on the card slot could be a cause of problems I guess, but mine have been fine. I believe a couple of people have had transformer failures though, which would be more problematic to sort out (although I guess you could get it rewound).

If you are thinking of buying one, I'd suggest collecting in person. The tester is very heavy, and the full boxes of test cards are rather heavy too. Carraige on something like this would be expensive, and many eBay sellers would not have the facilities to pack it properly (a pallet may be the best idea).

I hope that's some help!
Paul.
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Old 7th Apr 2005, 10:35 pm   #3
tvden
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Wink Re: Buying a Valve Tester

Hi Paul R, I think it all depends on how much use you have for a valve tester and how much you are prepared to spend on one, I had a Avo MK1V characteristic tester a very nice machine one I could not fault, the only trouble was that it sat on the shelf a lot, and at £500 pounds !!! I felt it was wasted money so I sold it, and bought a Taylor 45c off of ebay last year for £60, a bargain, the taylor 45c is not as good as the Avo but does the job and tests most valves, and its still a charactistic meter, for myself I have found the Taylor 45c to be good value for money and have been very happy with mine in my opinion the taylor is a good middle of the road tester very easy to use as oposed to the Avo which is more fiddly,the taylor is not a heavy machine and easy to post, I think at the moment most valve testers are down in price from last year !!! good Taylors were fetching £200 on ebay so a good time to buy, regards Den

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Old 8th Apr 2005, 5:43 pm   #4
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Default Re: Buying a Valve Tester

Thanks Paul and Den,

I probably don't have a great deal of use for a tester if you look at it objectively, I would just like one! I usually justify this sort of thing by saying it can be a birthday present!! I bought a signal generator a couple of years ago. I very rarely use it, but I love just having it - try explaining that to my wife!

I wonder whether the Mullard might be a bit cumbersome with all the cards, but I am very tempted by a Taylor 45C as they seem to go for somewaht lower prices. Will this test all the valves I am likely to need for 1950s and maybe 30s radios? I am concerned about buying something only to find that it will not test the later valves.

Thanks

Paul
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Old 8th Apr 2005, 6:18 pm   #5
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Default Re: Buying a Valve Tester

Yes, the Mullard certainly takes up a fair amount of space. You need somewhere to leave it out, as it's far too heavy and bulky to be fetching it out when you want to use it

Fortunately my workshop is the smallest bedroom and has a recessed alcove above the stairs with a "floor" at about table height (probably intended as a baby nappy changing area) which is just the right size for the tester and two boxes of cards. It's also the sort of space that's not much use for anything else.
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Old 8th Apr 2005, 6:53 pm   #6
PaulR
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Default Re: Buying a Valve Tester

Yes, we had a very similar room, but the baby who used to have his mat on the useful shelf thing is now 18 and he takes up all the room!! I saw the pictures of your workshop at the weekend whilst following a fascinating thread about the mains supply and isolating tarnsformers. I'd really like something like that.

I think I might go for a Taylor if I see a suitable one. Wait for the new thread entitled "My Valve Tester Won't Work"!

Thanks

Paul
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