[Heathkit] DX-100

[Kenneth G. Gordon]

On 28 Dec 2007 at 23:24, Ben Davis wrote:

> I am trying to restore a DX-100 and I want to replace the parts in the
> VFO while I have it apart but I can not find any of the Silver mica
> capacitors.

Why do you want to do that?

> Has anyone replaced all of the resistors and capacitors in the VFO

I have several VF-1s. I much prefer them to the HG-10(*). They are more 
stable and key better.

The VF-1 is the exact same VFO as that in the DX-100. I have never had 
any trouble with any of the silvered mica caps in any of them, and have 
never had to replace a resistor except the HV dropping resistor for the VR 
tube.

I HAVE had trouble with the 4.5 - 25 pfd ceramic trimmers though. 
Recently, a bad one caused the VFO to annoyingly jump frequency 
periodically.

As Glen Zook suggested some time ago, replace the 6AU6 with a 6AH6, 
and the 0A2 with a 0B2. The VFO will be far more stable, and key cleaner.

There originally were two different types of bandswitch included with those 
VFOs: one was all phenolic, and the last section was ceramic in a later 
one.

I have found that the phenolic bandswitches can cause frequency jumping 
unless they are scrupulously clean, and unless you wiggle the knob back 
and forth a bit when switching from 160/80 to 40 and up.

Also, if you parallel the 4.5 - 25 pfd ceramic trimmer which is under the 
chassis (only used for 11 meters) with an about 115 pdf silver mica cap, 
the VFO can be adjusted to tune from about 4.95 to 5.25 Mhz, thus giving 
you coverage of 30 meters. Depending on the rig, you have to then use 
either 40 meters or 20 meters to tune up on 30 meters. You have to 
experiment a bit.

Lastly, you can easily convert the VF-1 or its DX-100 equivalent to 
blocked-grid keying by following the directions here:

http://www.mines.uidaho.edu/~glowbugs/vfo.html

and click on the VF-1 link.

Ken Gordon W7EKB