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speakerfritz 10th December 2010 08:19 PM

Mercury 1000/2000 KT-88 and 6l6 design bug
Well it turns out that the Mercury 1000/2000 has a design glitch. It can test 5881, el34, 8417, 6550's for transconductance, but seems to only offer emmissions testing for KT-88's and 6l6's.

A lot of folks are just using 5881, el34, 8417, 6550's settings and changing the load, to test KT-88's and 6l6's for transconductance.

Having played around with this whole family of tubes recently, my first thought was that the tester can not handle the current of a kt-88 or 6l6.

I took a look at the schematic and don't think it's a voltage bias problem since the tester can test 8417's. The schematic is available here to large in size to post

Pacific T.V. - Online Schematics

So my thinking is that it's a transformer current problem. WOndering if I add a 15 volt transformer where indicated, if that would help?

Also thinking, sure I'll have to re-calibrate, maybe I can plus up the bais DC quality using bigger caps, which might get me some more current for a short term test.

Anyone cross this bridge?

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