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Homebrew Equipment A place to show, design and discuss the weird and wonderful electronic creations from the hands of individual members. |
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23rd Aug 2013, 5:50 pm | #1 |
Nonode
Join Date: Jul 2010
Location: Folkestone, Kent, UK.
Posts: 2,172
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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! |
23rd Aug 2013, 10:27 pm | #2 |
Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,535
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Re: Yet another valve tester
I reckon that's an "Essex" not an "East Kent"
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23rd Aug 2013, 11:22 pm | #3 |
Octode
Join Date: Jan 2005
Location: Hyde, Greater Manchester, UK.
Posts: 1,074
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Re: Yet another valve tester
Very nice reuse of an old pc psu case there, looking good.
Jay
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23rd Aug 2013, 11:38 pm | #4 |
Nonode
Join Date: Jul 2010
Location: Folkestone, Kent, UK.
Posts: 2,172
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Re: Yet another valve tester
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! Last edited by ITAM805; 23rd Aug 2013 at 11:43 pm. |
8th Jul 2015, 6:48 pm | #5 |
Triode
Join Date: Jul 2015
Location: Pickering, Ontario, Canada
Posts: 33
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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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18th Jul 2015, 12:48 pm | #6 |
Nonode
Join Date: Jul 2010
Location: Folkestone, Kent, UK.
Posts: 2,172
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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. |