DX-100 Load Control Mod

[Tuber]

Hi All:  I am rebuilding a DX-100 (not a 100B) for a friend and want to incorporate the Load Control Mod that replaces the step switch and the incremental 200pf capacitance steps.  I've read there is a mod where you can install a 3 gang variable capacitor ++ to improve that circuit.  Would anyone out there have the info/parts/schematic on how to do this??  I don't see it in the DX-100 Mods I have read about.  Thanks very much. 73s, Steve 

[WQ9E]

Steve,

You can basically just refer to the DX-100B schematic and use the parts/connections shown there.  The modified DX-100 has the same loading circuit as the B variant.

If the original circuit (switch and fixed capacitors) are still OK then it will be fine as is.  Like the Valiant, the switch contacts are easy to burn if the fixed loading is switched while RF is applied.  The original circuit does have the ability to match a slightly wider range of antenna impedance/reactance.

[Tuber]

Thanks for the quick reply, Rodger.  I take what you say to mean that if the switch contacts aren't burned after all these years of switching with RF there, then keep using it without converting to the mod.  I also infer than those 200pf caps in the mushroom looking assembly are good and sturdy and not a source of trouble.

OK then, I will check it out closely.   Thanks for the info and steer to the 100B schematic, just in case.
73,s Steve

[Tuber]

I can't locate a schematic for the DX-100B on the Web........would you or anyone else out there have one they could scan and email me?  I'd sure appreciate it!!  Thanks, Steve

[SA7AUY]

DX-100U (the British version) use a 3x500pF variable capacitor (C37).

/ SA7AUY

[Tuber]

SA7AUY + WQ9E:  Thanks very much!!!
best 73s, Steve