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 Valve/CRT testers, any good?
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 Return to top of page · Post #: 1 · Written at 10:17:37 AM on 3 February 2012.
scorezero's Gravatar
 Location: Bentleigh East, VIC
 Member since 4 January 2012
 Member #: 1055
 Postcount: 39

Hi all,

I was reading about valve testers as they seem like a great idea in our field.

I saw this info online where the guy basically says that they're a waste of time:

http://www.jacmusic.com/Tube-testers/index.html#FineScale

His English isn't perfect, but you get the idea. And he has some for sale! A bit of a head scratcher this one. If anyone here can suggest a good tube tester to look out for in terms of brand and model, it would be really useful.

Cheers,

Adam Smile


‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
"What's that big box by the back door? You didn't buy another old TV from eBay did you?"

 
 Return to top of page · Post #: 2 · Written at 10:19:42 AM on 16 February 2012.
Little Nipper's Gravatar
 Location: Australia, SA
 Member since 21 December 2011
 Member #: 1047
 Postcount: 85

Greetings,
Although I am no expert on this I can give you my opinion.
When I was a school kid I asked a radio repairman this and he said he did not have one because they did not test a valve properly. I have since heard that there are two or three different aspects you can measure and a valve tester will only test one of these.

I use a CRO to test mine as I can see exactly what is happening under working conditions. With a Signal Generator and a Volt Meter you can test the actual gain of each stage.

I think Valve Testers were made for corner shops and unskilled people to use, much the same as battery and cell testers are used today in corner shops. You take your suspect valve to the shop, measure it then measure a new valve and compare readings. If they measure differently, you buy the valve but if they measure the same you take your equipment to the radio repair man.

I have been trying to purchase a Valve Tester for awhile now, just to play with one but $50 is my price limit and they sell for around $300. You can purchase a lot of parts for $300. I recently purchased a 100MHz CRO for $200 which I can use to test everything electronic. I did not need another CRO but oneday 100MHz may come in useful.

If the average price of a valve is $20 you could buy 15 new valves for the price of the tester. How many years does it take you to buy an average of 15 valves?

I hope this has put things in perspective for you.


Regards, LN


 
 Return to top of page · Post #: 3 · Written at 11:56:16 AM on 16 February 2012.
Brad's avatar
 Administrator
 Location: Greenwich, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 6663

I would like to have a valve tester but I don't for pretty much the same reasn - too expensive for the amount of time it'll get used.

The other thing is that when I am satisfied that a radio should work I plug the valves in, fire it up and if it doesn't work I check to see if a heater is not working. If all is well I then wriggle the valves to check for bad socket connections. If there is still no noise I change each valve, one by one, until there is a sound. If there is still no sound I usually assume that I have either missed or stuffed something in the rest of the circuit and then backtrack.

Nine times out of ten I manage to get a radio I restore running without all the fancy gear and I usually tweak the coil grubscrews by ear too.

It's just like tuning an old Holden red motor if you don't have an engine analyser. You just get the correct gap on the points with a feeler gauge then turn the dizzy until the engine runs smoothest.


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A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 4 · Written at 8:18:56 PM on 21 February 2012.
scorezero's Gravatar
 Location: Bentleigh East, VIC
 Member since 4 January 2012
 Member #: 1055
 Postcount: 39

Thanks guys, I have also read about how testers don't always measure every aspect of a valve's operation. Some of the better ones can reportedly test more accurately, but who knows. I notice that some specifically mention that they can test 12AX7 and 300B valves, these are obviously tricky because of their dual functions.

A CRO is definitely on the shopping list!

Cheers,

Adam


‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
"What's that big box by the back door? You didn't buy another old TV from eBay did you?"

 
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