[AMRadio] Too much HV

[James Liles]

Hi Todd:
The 866 needs to be warmed up to vaporize the mercury or they will ARC over. 
Maybe too fast on the HV switch.

Kindest regards Jim K9AXN

-----Original Message----- 
From: wb3fau at att.net
Sent: Tuesday, November 15, 2011 8:04 PM
To: Discussion of AM Radio in the Amateur Service
Subject: Re: [AMRadio] Too much HV

I  agree  with you Todd. Some  years  back, i  had  silicon in  my t-368F.
one shorted out and the other opened.  i  put in 3B28s and never had any 
trouble after that.  Russ.

--- On Tue, 10/18/11, Todd, KA1KAQ <ka1kaq at gmail.com> wrote:

> From: Todd, KA1KAQ <ka1kaq at gmail.com>
> Subject: Re: [AMRadio] Too much HV
> To: "Discussion of AM Radio in the Amateur Service" 
> <amradio at mailman.qth.net>
> Date: Tuesday, October 18, 2011, 10:58 AM
> 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
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