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Ed_Dinning · 19th Feb 2006, 11:40 am

Hi Gents, this sounds like a MUllard "TRAP" if you obey the instructions and only use A&B all is OK, BUT presented with 3 cards the tester is likely to try to use all 3 with the results mentioned. I assume A,B,C cards are used to test a full wave rect with a different type number as well. These testers were often used by unskilled people in shops so I'm not surorised it caused problems.
This is probably the foundation of the warning about a rouge card that started in the 50's.
A worthwhile mod, that I carried out on my tester was to add fuses in all the HT transformer output windings (about 10 in all). These will then pop with a problem like this and prevent damage to an irriplaceable transformer.
The main trip and fuses will not always blow under these conditions.

Ed

19th Feb 2006, 11:40 am	#32
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,194	Re: Mullard Valve Tester Card Project Hi Gents, this sounds like a MUllard "TRAP" if you obey the instructions and only use A&B all is OK, BUT presented with 3 cards the tester is likely to try to use all 3 with the results mentioned. I assume A,B,C cards are used to test a full wave rect with a different type number as well. These testers were often used by unskilled people in shops so I'm not surorised it caused problems. This is probably the foundation of the warning about a rouge card that started in the 50's. A worthwhile mod, that I carried out on my tester was to add fuses in all the HT transformer output windings (about 10 in all). These will then pop with a problem like this and prevent damage to an irriplaceable transformer. The main trip and fuses will not always blow under these conditions. Ed