W1VZR DX100B mods

[W1DAN]

Hi Folks!

As Peter W1VZR is now an SK, I figured I would scan and publish his Heathkit DX100B modifications that he did for Peter W1ZZZ on August 28 2001. I found this at Peter's QTH a few weeks ago.

Pretty good job, but TOP Secret! :-)

Dan
W1DAN

[Opcom]

Took a liberty and redrew using LTspice. New ink for old eyes.

There are some unmarked values and I'm not getting the keying circuit relay coils voltage rectifier. DX-100 users probably know what's going on there.

2024-02-22 replaced file with corrected file
2024-05-27 replaced file with corrected file to include corrections from the discussion.

Updated the schematic incorporating the valuable comments as Notes and changed the component reference designations so that the original part locations are called properly in comparison to the DX-100B schematic, but reflect the special values of the modifications, and so that all of the added parts start with '100' series so added parts are clear.

[Detroit47]

Patrick

R2 is to low for anything like a D104 it should be 4.7 meg or 5.6 mrg.

Johnathan N8QPC

[Opcom]

No argument here. Wonder what was intended in the modification?

[DMOD]

No argument here. Wonder what was intended in the modification?

Nice schematics Pat, thanks.

The resistance is low enough for a "Line-IN" source from a processor or one of the old mid-impedance mics.

[Tom W2ILA]

R2 was probably intentionally kept low.  W1VZR always ran an MRF102 preamp in the bottom of D104 mics so that it had a nice high impedance to look into.  His FET preamp schematic was also a top secret at one time.  

It was a more successful approach than putting a 5 meg at R2 in DX100's and Valiants and then having to troubleshoot the hum that occasionally popped up.  

[W1DAN]

Hi Patrick:

Thank you for re-drawing the schematics. I have the original paper in my hands, and can say that:

1. C6 is 330pf
2. Question mark ("?") and lines near the driver transformer can be deleted. This was a white-out correction that Peter did.
3. R18 is 2.2k
4. Duno what the value of R17 is, probably original at 0.1 ohm as R16 or R35 in the original DX100B schematic.
5. Pin 9 of the 12BY7 driver may remain grounded as seen in the original DX100-B schematic:

https://wa3dsp.org/heath/dx100/DX-100B_schematic.pdf

Again, thank you. I miss Peter on AM.

Dan

[Opcom]

It's nothing, just some drawing! I replaced the file with a corrected one and appreciate the comments. LOL even got a new tube .asy file out of the deal as the 12BY7 has a center tapped heater.