DX-100 grid current flicker

[Brian Wood]

I just noticed that the DX-100 I restored has something funny going on with
the grid current. It's especially noticeable on 10, but it does it on other
bands to a lesser extent. The grid current seems to flicker - it'll start at
5 mA, then suddenly jump to 4 or 3 mA then back up. Sometimes it'll just
drift gradually down and then suddenly jump back up. I replaced the meter
switch, modified the drive pot circuit and replaced the finals, all to no
avail. Can't convince myself the bandswitch is dirty. Crystals do it too, so
it's not the VFO. DC bias voltages are rock solid. Meter itself is good (I
disconnected it and put a dmm in there and it also flickered.)

I'm kinda lost as to how to explain this without a good HF scope and RF
probe, which I don't have. I think the grid current really is doing this,
and since it's not DC, it has to be the actual RF drive is flickering. So it
could be the 12BY7 xtal osc/buffer or 5763 driver stage, or maybe the
coupling cap to the driver. Or???

73,

Brian, W0DZ

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