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retailer · 10th Jun 2021, 3:47 pm

I've had the control panel of a 2 panel tester for some years waiting for a socket panel to turn up at a reasonable price - looks like it isn't going to happen so I may make a banana plug and patch lead type of valve socket panel, however I hadn't ever powered up the control panel so I pulled it out of it's box (the same one it arrived in from Ebay newspaper packing is dated 2003) I hooked up a 6V6 to see if it worked or had issues, the 40 ohm meter swamp resistor was OC so I fitted a temp 40 ohm in it's place, it does seem to work but on checking voltages I found the anode voltage right up at 364V, some more probing and I found most of the anode voltages are over voltage by around 65%-70%. The anode/screen transformer has the correct 232V on the primary, all of the screen voltages are within 5%-7% it is only the anode voltages that are affected. The 12V and 30V are ok and within 10%, the voltages I measured are:-
80V is 109V 37% over
100V is 154V 64% over
125V is 177V 70% over
150V is 208V 72% over
200V is 292V 68% over
250V is 364V 68% over

Leaving it on for 30 min, the transformer did not even get slightly warm, I thought that maybe the transformer was OC between the taps and my DMM was getting some sort of capacitive coupling causing strange readings but a quick check with an Avo 7 found the voltages matched those I measured with the DMM. The circuit shows one continuous winding with taps, but as some of the voltages are duplicated it looks as if there maybe two sets of windings one for screen and one for anode, just wondering if anyone has any ideas.

10th Jun 2021, 3:47 pm	#1
retailer Heptode Join Date: May 2005 Location: Adelaide, South Australia Posts: 541	AVO two panel tester strange fault I've had the control panel of a 2 panel tester for some years waiting for a socket panel to turn up at a reasonable price - looks like it isn't going to happen so I may make a banana plug and patch lead type of valve socket panel, however I hadn't ever powered up the control panel so I pulled it out of it's box (the same one it arrived in from Ebay newspaper packing is dated 2003) I hooked up a 6V6 to see if it worked or had issues, the 40 ohm meter swamp resistor was OC so I fitted a temp 40 ohm in it's place, it does seem to work but on checking voltages I found the anode voltage right up at 364V, some more probing and I found most of the anode voltages are over voltage by around 65%-70%. The anode/screen transformer has the correct 232V on the primary, all of the screen voltages are within 5%-7% it is only the anode voltages that are affected. The 12V and 30V are ok and within 10%, the voltages I measured are:- 80V is 109V 37% over 100V is 154V 64% over 125V is 177V 70% over 150V is 208V 72% over 200V is 292V 68% over 250V is 364V 68% over Leaving it on for 30 min, the transformer did not even get slightly warm, I thought that maybe the transformer was OC between the taps and my DMM was getting some sort of capacitive coupling causing strange readings but a quick check with an Avo 7 found the voltages matched those I measured with the DMM. The circuit shows one continuous winding with taps, but as some of the voltages are duplicated it looks as if there maybe two sets of windings one for screen and one for anode, just wondering if anyone has any ideas.