----- Original Message -----
From: "Jim Thomson" <jim.thom@telus.net>
To: <amps@contesting.com>
Sent: Sunday, October 31, 2010 5:29 AM
Subject: [Amps] HV rectifier strings - to bypass or not?
> Date: Sat, 30 Oct 2010 20:50:37 -0400
> From: "Carl" <km1h@jeremy.mv.com>
> Subject: Re: [Amps] HV rectifier strings - to bypass or not?
>
> White noise is real but in an amp with RX/TX relay isolation you wont hear
> it and it may not occur with big diodes.
>
> It is noticable with SS receiving and audio gear and a single .01 or so
> bypass across each leg of the rectifier takes care of it.
>
> ## Ok, so 10,000 pf across each of the 4 x legs.
** You will see these in most rigs, entertainment gear, etc. I can hear it
from the usual 12VDC supplies used to feed transverters and VHF/UHF bricks
because the backround noise is so low.
>
> I like to add a SINGLE .0047 across the full string in an amp and another
> at
> the output to ground to keep any high intensity and transformer stretched
> spikes from bothering the diodes or electrolytics. The one to ground also
> catches any stray RF that the plate choke or its bypass missed.
>
> ## whoa. Where exactly is this 1st .0047uf wired to and from ? What
> do you mean by... "across the full string" I lost you some where.
** Redraw each string to represent one diode, use one cap across it; tht
woould be 2 caps in a doubler and 4 in a FWB. I went with a .0047 as it
appeared to work best with what I saw on the scope. This was a stand alone
PS, no amp involved. Yes, Im using 10-15KV caps which is cheap insurance for
the even one time they are needed. As I said earlier, my lines are not the
best around and the utility company does very little PM unless forced to.
Having power kick off and on in a few seconds is a regular occurance.
** National used a .1uF HV secondary bypass on several radios that saw
commercial/government service in countries with poor utilities. Without the
cap the tube rectifiers would short taking out transformers. Now those leaky
paper caps take out transformers! Now the USA has 3rd world utilities (-;
>
> ## BTW, these 1N5408's + 6A10's will typ hi-pot test to 1.4 kv.
** Thats not much overhead, whats the worse case?
Carl
KM1H
>
> Jim VE7RF
>
>
> Carl
> KM1H
>
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