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ukcol · 3rd May 2014, 10:26 pm

Hi Ed

Agreed, knowing what each switch contact in the matrix does is the key to solving this sort of problem.

Further investigation of the 713 card problem reveals that card C tests the same triode as card B (no surprise there) but, perhaps surprisingly, the voltages on the valve electrodes remain exactly the same whether using card B or C. There is also no change in the heater voltage.

It looks like the difference is going to be in the test limits as the emission test using card C shows a slightly higher reading than for card B.

If nobody has already done this I shall have to go through the manual and list what each contact does.

3rd May 2014, 10:26 pm	#92
ukcol Rest in Peace Join Date: May 2003 Location: Harlaxton, Lincolnshire, UK. Posts: 3,944	Re: Mullard Valve Tester Card Project Hi Ed Agreed, knowing what each switch contact in the matrix does is the key to solving this sort of problem. Further investigation of the 713 card problem reveals that card C tests the same triode as card B (no surprise there) but, perhaps surprisingly, the voltages on the valve electrodes remain exactly the same whether using card B or C. There is also no change in the heater voltage. It looks like the difference is going to be in the test limits as the emission test using card C shows a slightly higher reading than for card B. If nobody has already done this I shall have to go through the manual and list what each contact does.