Hello everyone!
I am working on a friends SB 200 amp. Works on 75, 40 and 20m. Has a slightly
negative grid current on 15 m and low output. A very negative grid current and
lower output on 10 meters.
Tubes are new ebay units. Unknown quality. The SB 200 uses a pair of 572Bs.
1.
My tube tester will not test 572Bs but I can test 811As. Can I use the same
tube tester set up to test the 572Bs?
2.
What is likely causing the negative grid current?
Thanks!
Alton, NU8L
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