[AMRadio] Too much HV

[Todd, KA1KAQ]

On Tue, Oct 18, 2011 at 10:47 AM, CL in NC <mjcal77 at yahoo.com> wrote:
> Other than using a variac or a boost buck xfmr, does anybody have a solid cure for the problem of excessive high voltage when 866's are removed and replaced with a solid state diode string?  I do not remember having this problem when I replaced 866's or 3B28's with the commercially made  direct plug in equivalent SS replacements, but only when modifying ham gear.  Bill, W4TYQ in Asheville, NC and myself are both working over a couple HA10 amps, and having to deal with 2500VDC on the plates of 4 811's instead of 1500 or so.  Both our amps came with the 866's already replaced, and we are toying with the idea of just putting 866's back in.

That's a pretty big spike! Sounds like something else is going on. I'd
be digging into those rigs and checking other things, like voltage
taps on transformers and such. An elevated line voltage will add to
it, but.......1000V difference??

The bigger issue beyond what should be a slight elevation in HV is
slamming the rig with full B+ without the built in soft start of using
tubes. MV tubes like the 866 and 872 have a habit of arcing as they
age, but the equivalent 3B28 and 4B32 don't have this issue, and only
change the voltage drop slightly. I've changed all my rigs using MV to
the Xenon equivalents and never had a HV problem since.

~ Todd,  KA1KAQ/4