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Old 23rd Aug 2013, 5:50 pm   #1
ITAM805
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Default Yet another Valve Tester

After years of fidling and fixing valve amps I never felt the need of a valve tester. My method has always been to sub a suspect one with a known goodun, job done.

But I've built up a stock old valves that all work, but how well they work is something I've never been too sure of?

Enter the "East-Kent Mk1" named with tongue firmly in cheek after the superb "Sussex" tester, highly regarded in this parish.

Circuit wise it's just a copy of Dave Ball's simple valve tester but with full wave rectification. The parts came from some generous folk hereabouts, ebay, Maplins and the junk box. As can be seen I've crammed it into an old ATX case and yes, there is an EL81 in there somewhere! It originally sported a nice 500 Volt digital display mounted on the case top, but I managed to destroy it fairly quickly, so it's presently lashed up to my trusty old Maplin DVM.

I repair the odd guitar amp for a local music shop and so there's only ever four types of valve ever likely to cross its path: 6L6/EL34, EL84 and ECC83. In fact my stock of old valves consist mostly of those types, hence it only needed an Octal and two B9A sockets and minimal switching to cover all bases.

I didn't have a spare 6.3V tx for the extra heater supply so it's derived from a 12V/2A wall wart which goes into an LM338T, trimmed for 6.3V - this gets quite hot with an EL34 plugged in!

I was rather pleased and somewhat surprised that it all worked first time, however I soon became somewhat bewildered by the test results. I think I need a bit more practice on it to be sure!
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Old 23rd Aug 2013, 10:27 pm   #2
Herald1360
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Default Re: Yet another valve tester

I reckon that's an "Essex" not an "East Kent"
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Old 23rd Aug 2013, 11:22 pm   #3
jay_oldstuff
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Default Re: Yet another valve tester

Very nice reuse of an old pc psu case there, looking good.

Jay
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Old 23rd Aug 2013, 11:38 pm   #4
ITAM805
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Default Re: Yet another valve tester

Quote:
Originally Posted by Herald1360 View Post
I reckon that's an "Essex" not an "East Kent"
Chris, in hindsight perhaps I should have named it "The Monet" - seeing as it's looks good from a distance


Thanks Jay, I knew that one day there'd be a use for those ATX boxes stacked up under the stairs!

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Old 8th Jul 2015, 6:48 pm   #5
Dan Payne
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Default Re: Yet another valve tester

Good to hear your homemade tube tester works. What were you surprised about when you went through your pile of tubes?
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Old 18th Jul 2015, 12:48 pm   #6
ITAM805
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Default Re: Yet another valve tester

Hi Dan, I was getting odd readings, this was due partly to an out of spec meter shunt plus my incompetence in using the instrument

The tester is now the 'MklV' and is in regular use, so if you looking for a simple emission tester, the circuit I used will do the trick.
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