Ending the Moment of Silence
David Wise is one of the most technically rigorous contributors in the R-390A community’s history. His signature achievement is the landmark document “R-390/R-390A AGC — Ending The Moment Of Silence,” hosted on r-390a.net, which dissects and solves a fundamental design flaw in the R-390A’s AGC speed switching circuit.
The problem was notorious among R-390A owners: switching the AGC from SLOW to MED position caused the receiver to go silent for several seconds before recovering. The effect was caused by the dual use of capacitor C551, whose charge state differed radically between AGC modes.
What makes Wise’s document exceptional is not just the solution but the methodology. He traces the engineering of the original circuit in exhaustive detail, explains precisely why the problem occurs, documents multiple approaches he tried and rejected, and arrives at an elegant modification grounded in deep circuit understanding. His willingness to show failed approaches makes the document uniquely valuable as both a fix and a teaching tool.
Larry Haney regularly directs newcomers to Wise’s AGC documents when AGC questions arise on the reflector, calling them essential reading for understanding a “major design flaw” in the R-390 family’s IF deck.
A Prolific Technical Voice
David was a prolific contributor to the R-390 reflector from at least 2002 through 2024 and beyond. He contributed detailed analysis on ballast tube replacement circuits, including designing a reverse phase control analog prototype for the 3TF7 ballast tube and working on a digital replacement that would simulate the original’s orange glow. He developed PTO endpoint adjustment techniques and tooling suggestions that were adopted by other contributors — Larry Haney photographed and credited Wise’s recommended alignment tool in his own Cosmos PTO Observations document.
He provided expert guidance on signal generator calibration, bevel gear repair using JB Weld and washer reinforcement for shrunken plastic gears, detent spring adjustment, and general receiver circuit theory. He is listed as a contributor to the Y2K Manual.
Key Contributions
- “Ending The Moment Of Silence” — definitive AGC mod document for R-390/R-390A
- Ballast tube (3TF7) solid-state replacement designs including analog and digital prototypes
- PTO alignment tooling and endpoint adjustment techniques
- Bevel gear repair methods for the RF deck mechanism
- Signal generator calibration and test equipment guidance
- Y2K Manual contributor
- Two decades of detailed technical analysis on the R-390 Reflector
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Mike Peace VK6ADA / r-390a.net Administrator
Compiled March 2026 from the Hollow State Newsletter, R-390 Reflector Archives, and r-390a.net FAQ