[time-nuts] 4 KV Power Supply Recommendations

J. L. Trantham jltran at worldnet.att.net
Mon Jan 18 03:13:34 UTC 2010


The more I read about this, the more I think I will just let it 'pump'.

This evening, the voltage on pin 4 is -1.039 VDC and the HV is up to 2151
VDC.

I was wondering how to limit the current capacity of an old HV transformer,
say 750 VAC, power supply and I suspect it is all in the size of the
capacitor.  I will have to do some calculations about that.  I was thinking
of using enough diode/capacitor units to multiply up to around 5 KV with a
variac to drive it and have taps from the diodes along the way for lower
voltages as well.  If I can just find my old transformers.  However, the way
work is now, I suspect the tube will be pumped down before I get around to
this.

I'll keep my eyes open for HV power supplies on eBay as well.

Thanks for all the info and I'll let you know what progress occurs.

Joe

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Stanley Reynolds
Sent: Sunday, January 17, 2010 8:38 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] 4 KV Power Supply Recommendations


Yes even with the mods odds are good the secondary is not well isolated from
the frame and even with the extra secondary windings the primary loading is
high per turn and load regulation is poor. Over all microwave transformers
are not very good, if you goggle them plenty of info and speculation about
them. If 
you have a matched pair you can turn then into a center grounded
configuration. There are ways to limit current and voltage like the
incandescent bulbs in the primary, or the autotransformer already
mentioned, but mistakes could be costly. HV resistors or strings of
resistors could also be used in the secondary to limit current. 

/ rambling on
Not sure working on very old cesium standards is very safe much less using
factory made PS at KVs to revive old tubes but some people jump out of
perfectly good air planes in the name of fun. HV power supplies are scary
and yes I have ended up on the other side of the room with a odd metallic
taste in my mouth, not sure why I lived so long ? $200 to ebay sounds better
than the cost to replace a time-nut, at least this one:-). If you do live to
see your homemade power supply working maybe your luck will hold with the
tube repair, did for me but I only got a few months of lock light and I'm
back to square one. / rambling off

Stanley



----- Original Message ----
From: Bob Camp <lists at cq.nu>
To: Discussion of precise time and frequency measurement
<time-nuts at febo.com>
Sent: Sun, January 17, 2010 7:33:16 PM
Subject: Re: [time-nuts] 4 KV Power Supply Recommendations

Hi

You also could leave the windings as is and feed the secondary voltage into
a voltage multiplier. Still not very safe to wire up. 

If you did wire it up, the available current would be pretty massive. I
certainly would not attach it to an ion pump I cared about.

Bob


On Jan 17, 2010, at 6:53 PM, Stanley Reynolds wrote:

> 
> 
> 
> 
> ----- Original Message ----
> From: Chris Stake <stake at btinternet.com>
> To: Discussion of precise time and frequency measurement 
> <time-nuts at febo.com>
> Sent: Sun, January 17, 2010 5:05:01 PM
> Subject: Re: [time-nuts] 4 KV Power Supply Recommendations
> 
> What is the operating voltage of the magnetron in a domestic microwave 
> oven? Although VERY HAZARDOUS, it might be possible to adapt the PSU 
> from an old one? Chris Stake
> 
> Yes, if you remove the transformer shunts and the filament windings 
> and add more primary windings in the space you would get about 2700v 
> with a full wave bridge. You also need to lift one side of the 
> secondary that is grounded to the frame. Yes very dangerous and yes 
> I'm luck to be able to tell.
> 
> Stanley
> 
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