Re: Hot diodes

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Gregory Hunter by way of Terry Fritz <twftesla-at-qwest-dot-net>" <ghunter31014-at-yahoo-dot-com>

Hi Gregg,

I've blown a diode string too, but it wasn't from
heat. I was running at 3200VA at the time, and I think
a rogue streamer missed the strike rail and hit a
power supply line on the floor. I'm using 1N4007's,
and they don't get warm even on longish runs. Of
course, my MOTs self-limit at about 750ma.
Additionally, the MOT caps ballast the thing to no
more than 710ma. If I were in your place, I'd switch
to 3A diodes. Mouser Electronics sells them on-line
and cheap.

I wonder if this is just plain overcurrent heating &
failure, or if this is RF heating? Are you using a
filter? I bypassed my diodes with 500pF-at-20kv to give
the RF someplace to go besides through the diode
junctions. I also routed my DC through a couple of
output chokes to block the nastier spark gap products
(like VHF).

Solid state devices are the main soft spot in an
otherwise neat little power supply. This is probably
the best argument for using a MOT stack of 4 or more
xfmrs and no electronics.

Regards,

Greg
http://hot-streamer-dot-com/greg

--- Tesla list <tesla-at-pupman-dot-com> wrote:
> Original poster: "Gregg Adams by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <network-at-nexband-dot-com>
> 
> Hello all,
>  
> While I'm collecting up some more necessary items
> for my pig powered coil, I'm
> trying to stablize my MOT powered coil.  I am using
> the same MOT supply design
> as you'll find on Greg Hunter's page.  The problem
> is that the diode string is
> getting hot.  I have burnt one string out and
> noticed that the new one is
> getting very warm.  Is there any way to protect this
> string from heating up? 
> Can the string be placed in oil with the
> transformers?
>  
> Thanks,
> Gregg Adams
> 
> 
>