Chuck Rippel WA4HHG
r390a.com, the Practical Restoration Canon, and His Legacy to the R-390A Community

Section 1 — r390a.com: What It Was and Why It Mattered

r390a.com was Chuck Rippel’s primary contribution to the R-390A restoration community: a purpose-built website dedicated entirely to the practical restoration, alignment, and operation of the Collins R-390A/URR. At its height it was the most complete single-source reference for the receiver’s physical restoration — not the circuit analysis of the Hollow State Newsletter articles, but the tangible, hands-on process of taking a 60-year-old military receiver from unknown condition to calibrated operation.

The content of r390a.com addressed aspects of R-390A restoration that the TM-11 service manual, written for trained Signal Corps technicians, had never needed to address: how to identify the contract year and manufacturer from the nameplate and serial number; which components to service first and why; the physical disassembly and reassembly sequence that avoids damage to ageing mechanical parts; the photographs of what good and bad examples look like in situ; and the practical interpretation of the TM-11 alignment procedures for a restorer who does not have access to a military-specification test bench.

Archive Preservation

The r390a.com website, like many early community web resources, was not designed with permanent availability in mind. As hosting arrangements changed and domain renewals lapsed, the content became intermittently unavailable. The community recognised the preservation risk and the r-390a.net archive effort captured the material before it was lost. The preserved content is accessible through r-390a.net and cross-linked from this site. Restorers who need the r390a.com restoration documentation should use the r-390a.net archive copy; the original domain may or may not be active at any given time.

Section 2 — Contract Year and Manufacturer Documentation

One of the most practically useful bodies of work on r390a.com was Chuck Rippel’s systematic documentation of the differences between R-390A production runs by contract manufacturer and contract year. The R-390A was produced under military contract by four primary manufacturers — Collins Radio (Cedar Rapids, Iowa), Motorola, General Dynamics, and Stewart Warner — across contract years from 1951 through 1964. A unit marked with one manufacturer’s nameplate and a date code may differ substantially from another manufacturer’s unit of the same nominal specification in ways that matter for restoration, alignment, and parts sourcing.

Why Contract Year Matters in Practice

Rippel’s contract year documentation identified the following types of contractor-specific variation, all of which affect restoration decisions:

• Component sourcing differences. Different contractors purchased resistors, capacitors, and tube types from different suppliers. The specific carbon composition resistor types used by Motorola were from different manufacturers than those used by Collins, with different ageing characteristics. A restorer who knows the contract year can look up which specific component types were used and what failure pattern to expect.
• Mechanical assembly differences. The manufacturing tolerances and assembly sequences differed between contractors. Some contractors had tighter worm gear mesh than others; some used slightly different oscillator deck coupling arrangements. These differences affect how a unit responds to the TM-11 alignment procedure and what adjustments are required to achieve compliance.
• Circuit modification history. Units produced under later contracts incorporated changes from TM-11 Change documents; earlier units may be in original unmodified condition or may have been updated in the field. Rippel’s documentation provides a baseline for what a unit of a specific contract year should look like in unmodified condition, allowing field modifications to be identified and evaluated.
• Serial number and nameplate identification. The relationship between serial number ranges and contract years is documented, allowing a restorer to determine the production context of any unit from the nameplate information alone.

Section 3 — Specific Technical Contributions

• R620
  POT
  R620 Audio Gain Potentiometer — Taper Standard and Correct Replacement The AF GAIN (audio gain) control in the R-390A is a potentiometer designated R620 in the TM-11. Like all audio gain controls in tube equipment, it uses a logarithmic (audio) taper rather than a linear taper, so that the perceived volume increase as the knob is rotated feels approximately linear to the human ear. Rippel documented the specific taper characteristic required for the R-390A application, the consequences of installing a linear-taper replacement (the volume control becomes nearly all-or-nothing rather than smoothly progressive), and the correct specifications for sourcing a suitable replacement. His documentation of this apparently minor detail has prevented a large number of restorers from installing linear-taper substitutes that appear to work but make the receiver uncomfortable to use at low volume settings. The R620 taper standard is now standard community knowledge, but it arrived in that status through his published documentation rather than through any other source.
• B+
  RISE
  B+ Rise Rate as a Bleeder Diagnostic — A Practical Field Test One of Rippel’s most elegant practical contributions is the B+ rise rate diagnostic: a method for assessing the health of the R-390A bleeder resistor network without measuring resistance values directly. The technique observes the rate at which the B+ supply voltage rises after switch-on. In a correctly functioning unit with correctly valued bleeders, the B+ rises at a characteristic rate determined by the RC time constant of the filter capacitors and the bleeder network. A bleeder network whose total resistance has drifted high (a common carbon composition failure mode) allows B+ to rise faster than it should, because the minimum load current is lower than designed. Rippel documented the expected rise behaviour for a correctly restored unit, providing a field-observable baseline against which any unit can be assessed without special test equipment.
  
  The complementary technique — the timed decay test after power-off, to verify the bleeders are safely discharging the filter capacitors — is documented in the vk6ada.com.au R-390A Bleeder Resistor Reference post, which cites Rippel’s rise-rate work as the original practical framing of both measurements. Together, rise rate and decay rate provide a complete practical characterisation of bleeder network health without requiring the bleeder resistors to be removed or measured individually.
• REST
  SEQ
  Practical Restoration Sequencing — The r390a.com Order of Operations Perhaps the most directly actionable content on r390a.com was the restoration sequencing guide: an ordered sequence of work steps for an R-390A restoration that minimised rework by addressing dependencies in the correct order. The principle is straightforward but poorly documented elsewhere: certain work creates verified baselines that subsequent work depends on. If you align the receiver before replacing the bleeders, you may need to re-align because the bleeder replacement changed the supply tap voltages. If you replace tubes before verifying the oscillator deck is mechanically sound, a subsequent oscillator deck repair may disturb the tube sockets. The r390a.com sequencing guide documented the correct order in concrete terms, from initial condition assessment through to final alignment verification.
  
  This sequencing guidance is distinct from the TM-11 maintenance procedure, which describes a fully equipped military workshop. Rippel’s sequencing is for the individual restorer working from the outside of an unknown unit inward, discovering faults rather than maintaining a known-condition receiver. The difference in starting point completely changes the optimal sequence, and his documentation of this distinction is something the TM-11 never addresses because it never had to.
• HSN
  REFL
  Hollow State Newsletter and R-390 Reflector Presence Beyond r390a.com, Chuck Rippel was a sustained contributor to both the Hollow State Newsletter (HSN) and the R-390 Reflector mailing list, providing the practical complement to Dallas Lankford’s analytical contributions in both forums. Where Lankford’s HSN articles described circuit behaviour from first principles, Rippel’s contributions described physical restoration observations: what the chassis looked like at various stages of restoration, which specific components showed the most consistent failure in units he had worked on, and the practical skill development required for the mechanical aspects of R-390A restoration — particularly the oscillator deck service, which requires a combination of mechanical precision and electrical measurement that the TM-11’s alignment procedure does not fully convey.
  
  His Reflector presence was characterised by the same practical orientation: when a restorer posted a fault description, Rippel’s response was typically a specific sequence of things to look at and touch, not an abstract circuit analysis. This complemented Lankford’s more analytical Reflector style precisely because the two approached the same receiver from different disciplines. A restorer who received both responses had a complete picture: what was theoretically happening and what to do about it physically.
• PHOT
  DOC
  Photographic Documentation — The Visual Record of R-390A Restoration r390a.com was notable in the early R-390A community for its photographic documentation of the restoration process. Textual descriptions of component appearance, correct and incorrect assembly, and the physical state of a well-restored versus poorly-restored unit are difficult to convey in the absence of reference photographs. Rippel supplied those reference photographs across the full scope of the restoration: before-and-after chassis cleaning, oscillator deck condition at various stages of service, the appearance of correctly re-soldered IF transformer shield lids compared to lids that have cracked or resettled, and the physical state of bleeder resistors after several decades of thermal loading. The value of this photographic record is difficult to quantify but is immediately obvious to any restorer who has tried to assess an unknown unit and needed a visual reference for “what should this look like?”

Section 4 — The Rippel–Lankford Complementary Pair

No assessment of Chuck Rippel’s contributions to the R-390A community is complete without addressing his relationship to Dallas Lankford’s parallel body of work. The two men approached the same receiver from fundamentally different disciplines across the same period of community history, producing a combined body of knowledge that is significantly more complete than either could have produced alone.

Dallas Lankford’s work is analytical and deductive: start with the circuit schematic, derive what the operating voltages and currents should be, identify which measurements distinguish between competing failure hypotheses, and publish the methodology so that others can repeat it. Chuck Rippel’s work is empirical and inductive: start with actual units, observe what they look like and how they behave, document what interventions produce what results, and publish the observations as a practical guide. Both approaches produce valid and useful knowledge; together they produce a complete restoration picture.

  ┌──────────────────────────────────────────────────────────────────────────┐
  │   THE RIPPEL–LANKFORD COMPLEMENTARY PAIR — R-390A KNOWLEDGE COVERAGE   │
  └──────────────────────────────────────────────────────────────────────────┘

  DALLAS LANKFORD                          CHUCK RIPPEL WA4HHG
  ─────────────────────────────────────    ────────────────────────────────────
  Approach:   Analytical / deductive       Approach:   Empirical / practical
  Question:   "How does it work?"          Question:   "What do I do with it?"
  Format:     Technical papers (HSN)       Format:     Restoration guides, photos
  Strength:   Circuit theory & math        Strength:   Physical restoration craft
  Tool:       DVM, schematic, derivation   Tool:       Scope, hands, camera

  WHAT EACH CONTRIBUTED TO R-390A KNOWLEDGE
  ┌────────────────────────────────────┬───────────────────────────────────────┐
  │  Lankford primary contributions    │  Rippel primary contributions         │
  │  ──────────────────────────────    │  ────────────────────────────────────  │
  │  AGC threshold analysis (C515/518) │  r390a.com full restoration reference  │
  │  PTO end-of-travel stop mechanism  │  Contract year + manufacturer ID guide │
  │  Bleeder 3-function documentation  │  B+ rise rate bleeder field test       │
  │  Slug rack frequency distribution  │  R620 pot taper standard + substitute  │
  │  Y2K R-390A Service Manual         │  Restoration sequencing order          │
  │  IF transformer thermal mechanism  │  Photographic condition reference      │
  │  Measurement-first methodology     │  Practical oscillator deck service     │
  └────────────────────────────────────┴───────────────────────────────────────┘

  WHAT THE COMBINATION PRODUCES
  ┌────────────────────────────────────────────────────────────────────────────┐
  │  Lankford provides:  The analytical framework for understanding faults     │
  │  Rippel provides:    The physical sequence for addressing them             │
  │                                                                            │
  │  A restorer with access to both:                                           │
  │  1.  Identifies the unit (contract year, manufacturer) — Rippel           │
  │  2.  Plans the restoration sequence — Rippel                              │
  │  3.  Makes baseline measurements (B+ rise, bleeder decay) — Rippel/both   │
  │  4.  Interprets anomalies from circuit theory — Lankford                  │
  │  5.  Selects and orders replacement components — Rippel (part ID)         │
  │  6.  Verifies AGC and sensitivity after restoration — Lankford             │
  │  7.  Documents results against community baseline — both                  │
  │                                                                            │
  │  The community archive preserves both bodies of work precisely because    │
  │  neither is complete without the other.                                   │
  └────────────────────────────────────────────────────────────────────────────┘

The Rippel–Lankford complementary pair: how the two primary R-390A community contributors’ work combined to produce the complete restoration knowledge base. The diagram is analytical rather than biographical; real restorations use both bodies of work in interleaved fashion, not in the strict sequence shown.

Section 5 — Contributions Reference

Chuck Rippel’s confirmed R-390A-related publications and contributions, as recorded in the r390a.com archive and community records. Archive access is via r-390a.net and the vk6ada.com.au HSN index at vk6ada.com.au/hollow-state-newsletter-complete-topic-index/.

Section 6 — Legacy

Chuck Rippel’s legacy in the R-390A community is most accurately described in terms of accessibility: he made a technically demanding restoration accessible to a far larger community of restorers than could have navigated the TM-11 alone. The barrier to entry for a first-time R-390A restoration dropped substantially when r390a.com provided the visual reference, the sequencing guidance, and the contract year identification that transforms a bewildering unknown-condition military receiver into a tractable restoration project with a documented starting point.

The specific technical contributions — the B+ rise diagnostic, the R620 taper standard, the contractor documentation — are individually significant. But the aggregate effect of r390a.com as a complete practical reference is harder to quantify and arguably more important: it represents the kind of community knowledge that exists only when someone with both the experience and the willingness to document it sits down and writes the guide that nobody else has written. Chuck Rippel did that, at a time when it mattered, and the community is measurably better at restoring R-390A receivers as a result.