[Heathkit] DX-40 question

Fri, 26 Dec 2003 09:36:43 -0600

Hello Mark,

Did you say you just did a solid state conversion for a VF-1?  That's on my
winter to-do list.  Do you have an article you can point me to for a
reference?  I have an article from Dec 72 QST that I was going to use, but
if you have something newer it would probably be a better mod.

I have a DX-35, and in the manual it says, "Pin 4 supplies B+ voltage
through a 20k 10w resistor.  This provides approximately 250 volts at 20
milliamperes." {for a VF-1}

So that means there's a 400v (20k x .02A) drop across the 20k / 10w
resistor.  That would put the 6146 plate voltage at 650v (250v at pin 4 plus
400v across the dropping resistor).

If you're planning on powering the solid state VF-1 from that, WATCH OUT!
That's a 650 volt source with a 20k impedance.  I don't know what voltage
you need for the VF-1, but the voltage you will get from pin 4 is:  650v -
(20,000 x I), where I is the current in Amps drawn by your modified VF-1.

If your mod is from that Dec 72 article, you'll be OK because the mod
includes two additional 15k / 5w dropping resistors and a 20v zener.

Hope this helps, and if you have any questions send me an email.  As I said,
the VF-1 mod has been on my list for years, and ... this is the year.

73,
ed - k9ew

----- Original Message -----
From: <[email protected]>
To: <[email protected]>; <[email protected]>
Sent: Friday, December 26, 2003 8:12 AM
Subject: [Heathkit] DX-40 question

>
>   Does anyone know the typical no-load/load plate
> voltage is on the 6146?  I have a schematic, but I can't
> read the printing, looks like 380 volts no load, and
> this seems low.
>  What I really want to do is determine the rated voltage
> at the acc. socket pin 4. I converted a couple of VF-1's to
> all solid state for a friend and I need to make a small
> change in the DX-40.
>
>
>
> Mark  WB8JKR
>
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