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Old 5th Nov 2018, 4:50 pm   #1503
Chris55000
Nonode
 
Join Date: Aug 2007
Location: Walsall Wood, Aldridge, Walsall, UK.
Posts: 2,853
Default Re: The "Sussex" Homebrew Valve Tester.

Hi!

For those who want or need to test series–operated valves in TVs or universal radios, etc., the traditional method of catering for these on valve–testers has always been to use multitudes of selecor switches and transformer secondary taps, etc., etc., which, in the 40s/50s was the only reasonable way of dealing with these types of valve, but as other Members have pounted out, rapidly makes expanding the "Sussex" to deal with series–operated valves a no–go in the traditional methods!

Now that economical semiconductors/modules are available it's time fo look at this problem afresh!

If you consider these valves again, the maker always stated "Sîeries Supply" for the heaters in their data, so instead of having to try and guess myriads of heater–voltages that might range from 3.6V to over 60V (leaving out such gems as the 117L7/117N7 for now!), we provide a simple high–voltage current controlled supply, with a simple selector switch in the current regulator giving currents of 100, 150, 200 and 300mA, with a simple Asian High Voltage Boost Voltage Converter Module, feeding a floating 7805 connected in Constant–Current Mode, with four resistors to select the current output.

A fourth 0–200V meter can then be added across the heater terminals to monitor the valve's heater voltage, and this test is also suitable for testing for partial s/c's across CRT heaters!

Circuit Information and parts list to follow when I've bought the module and tested it!

Chris Williams
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It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed!
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