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Old 20th Aug 2019, 11:46 am   #1
Triggermann
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Default Valve testers Is there a general use one?

I have just acquired an RCA AR88 and I am completely unfamiliar with this unit (but not valve equipment). I intend to restore it.

I do not possess a valve tester of any kind, and was thinking I should buy one, the question is... which one would be most likely to be useful on the AR88 valves?

thanks Andy
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Old 20th Aug 2019, 12:05 pm   #2
Station X
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Default Re: Valve testers Is there a general use one?

This is not what you want to hear, but you do not need a valve tester to restore an AR88.

The set itself can be used as a valve tester testing the valves under the conditions they subjected to in service. It's just a matter of taking voltage measurements and comparing them with the service data.

Even if voltage readings are wrong it's far more likely to be down to an electrically leaky cap or a resistor which has changed value than it is to a faulty valve. On the whole valves are very reliable.
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Old 20th Aug 2019, 12:07 pm   #3
Radio Wrangler
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Default Re: Valve testers Is there a general use one?

You do not need a valve tester of any kind.

Most often some quick voltage checks in the receiver will tell you whether a valve is pulling the right amount of current. If you have doubts, substitute a spare valve.

Valve testers come into theur own if you have a load of valves you want to sort into those worth keeping and those worth chucking.

For some reason the valve audio gang and the guitarists have latched onto valve testers and feel they need them for matching output pairs and for selling valves on auction sites. Demand from these people has sent the prices of valve testers through the roof, they feel they really really have to have one and they will spend whatever it takes.

Like any hifi thing, there is a rigidly ranked pecking order of what has the highest kudos/price down to things which are beneath their interest threshold. Oddly, these undesirable models still check valves perfectly well, but their ebay price-boosting function for the valves they test doesn't seem to work.

My best advice is don't bother
If you do bother, look for an older Taylor model.

The big money is in the later models, the metal octals in the AR88 don't need the later models. They are also very long lived valves.

I have a late model valve tester. I've had it so long it only cost me 20 quid! In all that time, I've never needed to use it on a set of my own. I've checked boxes of valves for the radio club, I've checked several valves I've bought as spares. That's it.

Note that valve testers have NO protection whatsoever against operator error or unfortunate setting of controls. It is very easy to burn out the coil in the meter. Replacement meters are not obtainable and fairly heroic measures are needed to arrange some form of alternative. One quick error can wipe thousands of pounds off of the value of a late model AVO VCM. Also, they are designed for use in quick bursts. Set up a test, press go, note the reading, and stop. Unfortunately, we've had the sad tales of people trying to use these machines to 'burn -in' valves and instead, they burn out the mains transformers in their tester.

This, of course, increases the rarity of good working testers, and the price of the rest goes up!

David
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Old 20th Aug 2019, 12:07 pm   #4
Triggermann
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Default Re: Valve testers Is there a general use one?

Graham & David, sounds fair enough. I've not needed once in the last 35 years, I just thought...…

Thanks for the prompt reply.

Last edited by Triggermann; 20th Aug 2019 at 12:18 pm.
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Old 20th Aug 2019, 12:07 pm   #5
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Default Re: Valve testers Is there a general use one?

Oh, well... At least we both agreed, Graham

David
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Old 20th Aug 2019, 1:40 pm   #6
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Default Re: Valve testers Is there a general use one?

...AND, once you get hold of a reasonably inexpensive, reliable valve-tester like the Heathkit TC-1/TC-2 models (Emission-testers) you'll need to do a renovation/calibration before you can rely on it.
I have 3 of them and each and everyone needed replacement of resistors drifted out of tolerance and I believe it will be the same with whatever you find, Taylor included.

Rgds,

/Torben
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Old 20th Aug 2019, 1:45 pm   #7
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Default Re: Valve testers Is there a general use one?

I mainly use my CT160, bought when prices were low, to test valves which I intend selling or passing on. Most of the faulty ones have inter-electrode shorts and you don't really need a valve tester to tell you that.
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Old 21st Aug 2019, 5:23 pm   #8
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Default Re: Valve testers Is there a general use one?

Quote:
Originally Posted by Station X View Post
This is not what you want to hear, but you do not need a valve tester to restore an AR88.

The set itself can be used as a valve tester testing the valves under the conditions they subjected to in service. It's just a matter of taking voltage measurements and comparing them with the service data.

Even if voltage readings are wrong it's far more likely to be down to an electrically leaky cap or a resistor which has changed value than it is to a faulty valve. On the whole valves are very reliable.
Way back, when I was first starting in this occupation, I thought I really needed a valve or tube tester. I got my first one when I was 14 yo. That was 61 years ago. I was a simpler emissions tester. When you gain experience, you find that the valves are the least of the problem.
I bought a new B&K Dynajet 707 in 1966 and still have it.
I'm generally working on some electronic project daily, but seldom use it.
There's generally other things wrong.
Dave, USradcoll1.
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Old 21st Aug 2019, 5:39 pm   #9
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Default Re: Valve testers Is there a general use one?

Quote:
Originally Posted by Station X View Post
This is not what you want to hear, but you do not need a valve tester to restore an AR88.
Why would he not want to hear that? Not having to pay out for more equipment is what we all want to hear!
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Old 21st Aug 2019, 5:47 pm   #10
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Default Re: Valve testers Is there a general use one?

Of course but these bits of kit have a "magnetic" attraction somehow, like an over expensive Hi-Fi that's not really essential-hence the high prices. Perhaps it all dates from the days when when it would be a mysterious semi-religious item on the counter of the Wireless shop available to few and a valve could be a truly expensive outlay... especially if it wasn't really needing to be replaced

Dave W
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Old 21st Aug 2019, 9:57 pm   #11
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Default Re: Valve testers Is there a general use one?

Many decades ago, when I was still at school, i used to Visit "Chadwicks" in Newcastle-U-Lyme. They had two valve testers, I think a Taylor and one other, maybe a USA model.
People would come in with their sixpences for valves to be tested.
20 years later, I took the 5 valves from my CTV set for testing. I was told some of the tests were pointless. It later transpired it was a faulty LOPT. A pal who worked for a German kiln manufacturer brought one back from Germany for me. It was a special import set, not one imported in bulk, and the supplying shop/importer had ceased trading.
Les.
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Old 22nd Aug 2019, 2:01 am   #12
usradcoll1
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Default Re: Valve testers Is there a general use one?

Quote:
Originally Posted by dave walsh View Post
Of course but these bits of kit have a "magnetic" attraction somehow, like an over expensive Hi-Fi that's not really essential-hence the high prices. Perhaps it all dates from the days when when it would be a mysterious semi-religious item on the counter of the Wireless shop available to few and a valve could be a truly expensive outlay... especially if it wasn't really needing to be replaced

Dave W
I have a few high quality valve or tube checkers. One is a US Government type similar to the Hickok offerings. It's a neat unit and in like-new condition.
I got a mess of used valves from a neighbor, so I ran them through the tester to see if they were worth saving. A few were rather desirable types, that I wanted to use them in the amps I was restoring.
Actually, testing the valves is a last resort when troubleshooting a non or poor performing piece of equipment.
A lot of experience proves this approach.
Dave, opinionated USradcoll1.
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Old 22nd Aug 2019, 8:49 am   #13
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Default Re: Valve testers Is there a general use one?

No matter what others say, I wouldn't be without my Mullard high speed valve tester. No setting up required, just slot in the relevant test card, pull the lever and you're away. CRT, so no meters to damage and there is an overcurrent cut out. Personally, I don't need stats, so the Mullard's 'serviceable'/'not serviceable' deduction works fine for me. It also indicates specific fault areas as the test progresses. I love it.
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Old 22nd Aug 2019, 11:35 am   #14
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Default Re: Valve testers Is there a general use one?

What is wrong for having too much test equipment?
I have a lot of them and it gives just as as much fun as collecting valve radios.
Even a 23 pounds Texscan VS20 wobble generator gives pleasure,because it costs me a lot brainstorming to get a decent sweep.
Just a good thing at my age.

Jard N.
(And off course a Jackson 648 valve tester)
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Old 22nd Aug 2019, 12:34 pm   #15
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Default Re: Valve testers Is there a general use one?

Andy,
Best bet would be to contact another AR88 enthusiast on the Forum & seek mentoring for your project. Maybe there are some of its valves which are prone to failing. Then perhaps you could contact another Forum guy near you who has a valve tester. There is bound to be someone on Merseyside or in Lancashire, if there isn't anyone on the IOM.
As the other guys have said, decent valve testers these days cost an arm & a leg. There is also a wealth of info available via "Search" on building your own.

Regards, David
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Old 22nd Aug 2019, 5:35 pm   #16
usradcoll1
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Default Re: Valve testers Is there a general use one?

Quote:
Originally Posted by stevehertz View Post
No matter what others say, I wouldn't be without my Mullard high speed valve tester. No setting up required, just slot in the relevant test card, pull the lever and you're away. CRT, so no meters to damage and there is an overcurrent cut out. Personally, I don't need stats, so the Mullard's 'serviceable'/'not serviceable' deduction works fine for me. It also indicates specific fault areas as the test progresses. I love it.
I forgot about my two RCA Card-O-Matics. I think the contacts need cleaning, as they're not always accurate, the readings aren't consistent.
Your Mullard tester must be a treat to see in operation! It only proves that Mullard always made the best.
Dave, USradcoll1.
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Old 23rd Aug 2019, 11:20 am   #17
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Default Re: Valve testers Is there a general use one?

You have a wonderful built in valve tester called a hand - let the set run for a few minutes, turn off all the power and feel the glass envelopes - if it's warm it's going if not it may be shot. Remove the valve, whip out the old multimeter set to ohms and test the heater pins for continuity.
In days of old there was even the dabbing a damp finger on the top caps of audio valves while which would give you a lovely blurk from the speaker if things were going BUT later valves put up to 600 volts DC on that top cap so you can see why the test fell out of popular use - but an insulated handle screwdriver/bit of dowling/plastic could substitute. Finally substitution of another identical valve is a good help (not allways I had two once that were totally shot and one was NOS). Like the above people I would suspect capacitors (especially grid coupling electrolytics), resistors (especially anode and even more in output stages as they fry up in the heat), pins/sockets (pull out valve squirt pins with contact cleaner and woggle up and down a few times) then finally the valve in question. This sequence is totally empirical and from my years of servicing but seems to pay off most times. Then go for voltages at pins while on etc.
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Old 23rd Aug 2019, 11:23 am   #18
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Default Re: Valve testers Is there a general use one?

You could of course build you own valve tester - there was a great thread here a few years back on building one. Practical wireless in the 60's had a design for one which used preprogrammed plug in boards and you can find those mags scanned and free to download on an American radio site if you google the name.
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