[Heathkit] HG-10 -VFO power supply, DX-60B

[Robert & Linda McGraw K4TAX]

First having restored several Heath DX-60 transmitters I would not suggest 
increasing the C value of the HV filter caps.  They were chosen for critical 
value Xc based on inductance of the secondary of the power transformer. 
Increasing the value can cause exactly the condition of voltage variation 
between keyed and unkeyed.  The HG-10 has an internal regulator which will 
keep the B+ at the correct value.  Obtaining power for the HG-10 from the 
DX-60B accessory socket should not pose any problems.

Normally, electrolytics decrease in value of C as they age.  This can cause 
excessive voltage changes between the keyed and unkeyed modes as the 
critical value of C does not exist.  After all the typical tolerance of a 
new electrolytic is some +/- 50% or more depending on brand.

I would however suggest that you replace the filter caps with 105 degree C 
units in place of the 85 degree C units originally supplied with the kit. 
The electrolytics will live a lot longer and will have a much tighter 
tolerance value of C.

As to the added TR switching function, I suggest you remove it and use a 
relay to do the TR switching.  My experience with tube type TR switching is 
that unless the tube is correctly biased to cut-off, they make wonderful TVI 
generators.  It is hard to beat a good Dow Key relay with a 115 VAC coil 
operated from the mode switch and accessory connector on the rear of the 
unit.

73
Bob, K4TAX


----- Original Message ----- 
From: <KHeck73 at aol.com>
To: <gzook at yahoo.com>; <nr5a at rap.midco.net>; <heathkit at mailman.qth.net>
Sent: Wednesday, December 21, 2005 1:07 PM
Subject: Re: [Heathkit] HG-10 -VFO power supply, DX-60B


>
> In a message dated 12/19/2005 11:11:56 A.M. Eastern Standard Time,
> gzook at yahoo.com writes:
>
> Actually, you don't want to run any
> external VFO from the internal  power supply of any of
> the old "boat anchor" rigs.  The voltage is  just too
> unstable between key up and key down.
>
>
> ..
> I recently obtained a HG-10B to use with my old DX-60B (which hasn't  been
> fired up in 30 years). I always wanted to try it with a VFO instead  of my 
> 3
> crystals! Would it help to replace the filter caps in the DX-60B  with a 
> larger
> capacitance value to help stabilize voltage to the VFO?
>
> Also, this DX-60B has an electronic T-R switch modification in  it. This
> involves an added tube, and was described in a QST article. I  could never 
> really
> use the T-R switch, though, because the transmitter signal  still got 
> through
> to the receiver so strong it was scary. Anybody familiar with  this
> modification?
>
> -Karl.
> _______________________________________________
> List Administrator: Duane Fischer, W8DBF
> ** For Assistance: dfischer at usol.com **
> $$ See the vintage area on the HCI web site - http://www.w9wze.org $$
> Heathkit mailing list
> Heathkit at mailman.qth.net
> http://mailman.qth.net/mailman/listinfo/heathkit
>