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ukcol · 18th Feb 2006, 11:55 pm

It has been mentioned that some mistakes were made by Mullard when they produced the cards which can damage the valve being tested and/or the tester. Having just restored a 7600/4 to working order I have identified one such mistake. In the first box of valves I was testing I came across a PY32 which is a half wave rectifier with an octal base designed for television. The Mullard card index lists the test cards as 967 AB but when I pulled out the cards there were 3, that is 967 ABC. To have 3 cards is usually the pattern for a full wave rectifier. Card A marked ELECTRODE (to test for shorts) and cards A and B one for each anode to check emission. Cards A and B worked fine and the valve tested OK, but when I tried card B, I switched off quickly when I was greeted with the very unhealthy sound of a lot of current flowing. So if you have a set of 967 cards, throw card C away and change the number of cards mark on cards A and B to 2.

18th Feb 2006, 11:55 pm	#31
ukcol Rest in Peace Join Date: May 2003 Location: Harlaxton, Lincolnshire, UK. Posts: 3,944	Re: Mullard Valve Tester Card Project It has been mentioned that some mistakes were made by Mullard when they produced the cards which can damage the valve being tested and/or the tester. Having just restored a 7600/4 to working order I have identified one such mistake. In the first box of valves I was testing I came across a PY32 which is a half wave rectifier with an octal base designed for television. The Mullard card index lists the test cards as 967 AB but when I pulled out the cards there were 3, that is 967 ABC. To have 3 cards is usually the pattern for a full wave rectifier. Card A marked ELECTRODE (to test for shorts) and cards A and B one for each anode to check emission. Cards A and B worked fine and the valve tested OK, but when I tried card B, I switched off quickly when I was greeted with the very unhealthy sound of a lot of current flowing. So if you have a set of 967 cards, throw card C away and change the number of cards mark on cards A and B to 2.