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Old 28th Nov 2008, 11:24 pm   #49
Electrical
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Join Date: Jul 2008
Location: Gateshead, Tyne & Wear, UK.
Posts: 336
Default Re: Mullard Valve Tester Card Project

Hi Ed, thanks for the offer, over the years I have collected 5 boxes of cards and at present I am short of about 215 cards. I checked this against my January 1966 Test Card Index list so I am sure there will be a few, more modern ones missing, as I am sure there must be a more modern list out there. I know the interface looks a bit big and cumbersome at present but at present I would like to see if the principal will work, that’s why I transistorised the relays so that if I ever get around to building a computer interface and find a way to multiplex all 130 relays the drivers are already there. When I connect it all up to a tester I feel sure there may be instability problems to solve first as I found when I built a jig to measure octal audio valves and applied a digital voltmeter to the grid. This is the reason I decided to make a simple diode matrix plug board to do the testing as I could end up with more faults in the computer programming and multiplexing, making it even harder to sort out. When it is complete and working, I will design a single PCB, with all the relays on an only use 400-volt 16A relays in the mains and HT rows. I am sure smaller 250 volt 7A PCB relays could be used in the base selection, so the size could be reduced considerably, also ULN2003 IC drivers instead of the resistor, transistor and diode drivers.
Dare I ask how far the complete list is off completion?
Regards Stan.
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