I bought four diode strings off eBay for really cheap. If I recall, they're rated at around 115 kV, 1 amp. They were immersed in oil for 115 kV, but I ran them at 15 kV as a full-wave bridge rectifier in air with no problem, after blowing up my first 34 kV DC PSU.
________________________________
From: Teslalabor <teslalabor@xxxxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Friday, August 22, 2014 8:00 AM
Subject: Re: [TCML] Submerged diode strings hold off distance (transfomer oil)
Hi Jim,
I don't think it's a good idea to mount the rectifiers inside the tank. It's
definetly not necessary to imerse them in oil neither for insulation nor
cooling purposes.
Another reason is: Maybe you will kill some rectifiers probably during some
initial tests so do you really want to pull out the transformer everytime
just for replacing dead diodes?
Regards,
Stefan
----- Original Message -----
From: "Jim Mora" <wavetuner@xxxxxxxxx>
To: "'Tesla Coil Mailing List'" <tesla@xxxxxxxxxx>
Sent: Friday, August 22, 2014 6:54 AM
Subject: [TCML] Submerged diode strings hold off distance (transfomer oil)
> Hello Group,
>
> Since I ordered and tested my Raytheon transformer fluid with a new Dexsil
> 40ppm test kit (available Forestry Supplies), I was pleased and bit
> surprised that it is well below the 40ppm PCB limit, in fact near the
> deepest purple on the lowest end of the test kit scale. It must have been
> maintained for duty and flushed several cycles as was evident when I
> opened
> it. It was military and under tagged FAA auspice after all.
>
> Therefore, I have reconsidered my design a bit to mount the rectifiers
> inside the tank. I removed the tall 12" horns for more space. And I seem
> to
> have ample room to mount my 6 pulse diodes strings recognizing there will
> be
> six pulse 12KV dc + to - to hold off at the ends. The strings (3) will be
> mounted horizontally as a stack and spaced to hold off the stress ~ 5KVac
> (H1,2,3 will go directly to the rectifiers at the isolated centers) and
> the
> ends (+,- 11KV) to any target. All 3 stacks will be joined at the ends for
> plus and minus 6 pulse DC. Doing this frees up my three HV horns on the
> top.
> One will connect to negative the middle horn will connect to the internal
> positive and deque diode junction. And the other side the farthest one
> will
> be dequed downstream positive to go to the external Charge Inductor. I
> will
> paint the base clamps Black, Yellow, and Red. Black is misleading as it is
> well below ground potential (2 HV leads will exit). I will probably ground
> the inductor tank and transformer together and may use 2 x-ray cables coax
> case grounded at the transformer and strip 12" or so off out at the spark
> gap. This has been an ongoing debate on the list unless it has been
> resolved
> in my absence.
>
> This gives me the option to experiment on top with different + to adjacent
> minus storage capacitance (stiffening if needed) and ripple suppression
> and
> a serious reminder to discharge a lethal, hidden energy source (it would
> have bleeder but time is an issue after T1). Hopefully such a cap will not
> be needed, but I like this external simple freedom of selection.
>
> Having said all that, and if you stayed with me (thank you), how far apart
> should the stacks be spaced to prevent flashover, and from other targets
> like the HV coils and grounded case parts. I would mount them equal
> distance
> in the center of the open space. I am more curious about the diode stack
> spacing. I don't have a lot of experience with real transformer oil and
> its
> dielectric strength.
>
> Before the transformer reconfiguration there was 24KV for Raytheon
> engineers
> to contend with and it was crowded in there!
>
> Thanks Much,
> Jim Mora
>
> Ha ha, I am beginning to wish I sold this as a serious retro horror movie
> prop or to the steam punk affectionaire. I do have (7) NOS JAN 8020
> rectifiers in original packing (40KV peak inverse) and vintage EF Johnsons
> sockets that will be for sale. The filaments are thoriated tungsten and
> glow
> pure white and instant on. Definitely old Frankenstein stuff! Those old
> >12"
> white ceramic horns and bases will be on the block too as will the hefty
> highly isolated 5V, 36 amp Filament transformer and maybe the 24KV 150H
> filter choke. It has been interesting working on something older than I am
> in great condition. This kind of device lends itself pretty well to EMP
> and
> was old school nuclear hardening. Forget about modern cars! It would be
> cock
> roaches and old diesel trucks still going ;-^)
>
> _______________________________________________
> Tesla mailing list
> Tesla@xxxxxxxxxx
> http://www.pupman.com/mailman/listinfo/tesla
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla