Whats it worth

[Glen Zook]

Heath offered at least 3 modification kits for the DX-100, 2 of which were also applicable to the DX-100B.

The first was the kit to change the switched fixed loading capacitor with the smaller variable capacitor loading to the continuously variable loading.  DX-100 transmitters that had this modification made were known as "DX-100A" transmitters.  That is the main reason that the next version was the DX-100B.

The second kit was for "improved keying" which also added a spotting switch to the front panel.  The modifications to the keying were to give a better "shape" to the r.f. envelope.  However, this modification also caused the VFO to run continuously when the "plate switch" was put in the "transmit" position.  Also, a hole had to be drilled in the panel to install the "spotting switch".

The third kit was to use the SB-10 SSB adapter with either the DX-100 or the DX-100B.  This kit also required drilling a hole in the front panel.  The DX-100B had the 2 holes for the SB-10 connections (2 each SO-239) drilled in the back of the chassis to install the kit.  You had to drill the chassis to install the kit in the DX-100.

The basic differences between the DX-100 and DX-100B are as follows:

The DX-100 had the switched fixed loading capacitors whereas the DX-100B had the continuously variable loading.

The DX-100 had 4 crystal control positions as well as the VFO.  These were switched from the front.  The DX-100B had only 1 crystal control position that had to be selected by opening the lid and moving a slide switch.

The DX-100 had the larger, "fancier", cabinet whereas the DX-100B had basically the same cabinet as the Apache, Mohawk, etc.

There were 3 capacitor values changed in the driver section of the DX-100B.  Those were to "improve" the drive on the 10-meter band.  Basically, they "helped" a "little"!  There was an article in QST telling which capacitors to change in the original DX-100.  Realistically, changing those capacitors helped, but not enough to bother with unless you were working on the transmitter for something else.

There were a relatively small number of various Heath units that were "factory made".  These were for use as demonstrator units at the Heath Stores that were located around the country.  Basically, these were not for sale, just for "samples" of the completed kits.

I have a Heath SB-110A 6-meter transceiver that was one of these "factory built" kits.  My unit came from the Heath Store that was here in Dallas, Texas.

The modifications that help stabilize the Heath VF-1 VFO also apply to the DX-100 and DX-100B.  If you replace the 6AU6 with a 6AH6 that helps considerably with the stability.  Then, replace the 0A2 screen voltage regulator with an 0B2.  This drops the screen voltage from 150 volts to 108 volts.  Both of these do not require any wiring changes.  If you use the 0A2 removed from the screen to regulate the plate voltage on the oscillator tube this helps stabilize the VFO even more.  This requires addition of a resistor as well as a 7-pin tube socket for the tube.

Glen, K9STH

Website:  http://k9sth.com


--- On Wed, 2/10/10, The Pollacks <rinkies at ATT.NET> wrote:

A big factor is whether it has been modified significantly, especially with extra holes in the panel.  There were a few common, reversible, and I think desirable mods, such as timed sequence keying and audio input section mods. (Mine has both).  Are the knobs original?  These are factors.
 
The 100B may be a bit more valuable than the 100, due to better loading control and a top cover that opens.  It's a project to get the 100 out of the cabinet!  I think there were fewer built, too.
 
I don't know that Heath offered a factory built DX100B.  At least the advertising of the period and Penson's book don't mention it.  Johnson offered the Valiant and Ranger in both factory and kit versions, and one way to tell them apart is that the factory versions had riveted tube sockets as opposed to nut and bolt fastening on the kits.


      

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