Collins 75S-2 — Serial Number & Production Guide
VK6ADA Technical Reference · Collins S-Line Vintage Amateur Equipment · March 2026 · Mike Peace VK6ADA
The Collins 75S-2 SSB Receiver was the second generation of the S-Line receiver series, introduced approximately 1962 and produced through approximately 1964–1965 at the Cedar Rapids, Iowa facility.[1] Building on the 75S-1 platform, the 75S-2 expanded the Collins Mechanical Filter bandwidth selection and served as the companion receiver to the 32S-2 transmitter. This guide consolidates serial number ranges, emblem transitions, manual edition history, and known circuit characteristics to assist collectors and restorers.
Overview & Specifications
Manufacturer | Collins Radio Company — Cedar Rapids Division, Cedar Rapids, Iowa |
Model Number | 75S-2 (Collins type designation: SSB/CW Receiver) |
Production Period | ~1962 – approximately 1964–1965 |
Receiver Type | Double-conversion superheterodyne with Collins Mechanical Filters |
Frequency Coverage | 3.4 – 30.0 MHz (amateur bands: 80, 40, 20, 15, 10 m) |
IF Frequency | First IF: 3.395 MHz; Second IF: 455 kHz (Mechanical Filter selectivity) |
Standard Mechanical Filters | 500 Hz (CW), 2.1 kHz, 3.1 kHz, 4.0 kHz — expanded bandwidth selection vs. 75S-1 |
Modes | USB, LSB, CW, AM (envelope detector) |
Sensitivity (SSB/CW) | ≤ 0.5 µV for 10 dB S+N/N |
Mains Supply | 115 V AC or 230 V AC, 60 Hz single-phase (primary wiring selectable) |
Companion Transmitter | Collins 32S-2 (also rare) |
Companion Amplifier | Collins 30L-1 Linear Amplifier |
Introduced | ~1962 [10] |
Collector Status | RARE — one of the lowest-production S-Line receivers. Matched 75S-2 / 32S-2 pairs especially sought-after. |
Important Note on Serial Number Sequencing
Per CCA historical research and a direct account from a former Collins employee,[9] Art Collins decreed that S-Line serial numbers were to be issued in random (non-sequential) order. For the 75S-2, the combination of low total production and random S/N assignment means serial number ranges are particularly uncertain. Physical inspection — emblem type, model designation on the serial plate, and internal component date codes — is especially critical for the 75S-2.
Collins Logo / Emblem Production Eras
The 75S-2 production concluded approximately 1964–1965, before the Collins emblem transition in Fall 1969. All authentic 75S-2 units should carry the Winged Emblem. A Round Emblem on a claimed 75S-2 is a significant authentication red flag.[3]
| Emblem Type | 75S-2 Applicability | Physical Description |
|---|---|---|
| Winged Emblem | Standard / expected on all authentic 75S-2 units. Production ended ~4–5 years before emblem transition. | Classic silver-and-blue winged Collins insignia. Two mounting holes flanking position if badge was ever replaced. |
| Round Emblem (any type) | Not applicable — authentication required if present. | Round Collins emblem — if present on a claimed 75S-2, verify serial plate, model designation, and internal date codes carefully. |
Serial Number Lookup Reference
Quick Era Identifier — Enter Your Serial Number
Documented Serial Number Data Points
| Serial Number | Emblem / Era | Notable Features | Source / Reference |
|---|---|---|---|
| ~1xx – ~1,xxx range | Winged | Early production; 1962–1963. 500 Hz, 2.1 kHz, 3.1 kHz, 4.0 kHz filter complement. Verify all four filter positions are populated with original Collins Mechanical Filters. | CCA survey data [4] |
| ~2,xxx – 3,xxx range | Winged | Mid production; c.1963–1964. Confirm all mechanical filters present and original. VK6ADA collection includes a 75S-2 — see vk6ada.com.au project page. | CCA survey / VK6ADA collection [12] |
Key Differences: 75S-1 vs 75S-2 vs 75S-3
| Feature | 75S-1 (~1959–1963) | 75S-2 (~1962–1965) | 75S-3 (~1964–1980) |
|---|---|---|---|
| Production Volume | Moderate | Low (rare) | High (most common) |
| Filter Complement | 500 Hz, 2.1 kHz, 3.1 kHz | 500 Hz, 2.1 kHz, 3.1 kHz, 4.0 kHz | 500 Hz, 1.0 kHz (3B/3C), 2.1 kHz, 3.1 kHz (base 3) |
| Companion Transmitter | 32S-1 | 32S-2 (also rare) | 32S-3 |
| Emblem Type | Winged only | Winged only | Winged, Transition Round, Small Round, Large Round |
| Collector Premium | Standard S-Line | Significant rarity premium | Standard (high volume); Winged Emblem premium |
Manual Edition History
| Edition | Date | Notes |
|---|---|---|
| 1st Edition | ~1962 | Original publication. Archived at Collins Radio Association (CRA).[1] |
| ~2nd–3rd Editions | 1963–1965 | Service bulletin amendments. Available via CRA archive: collinsradio.org. |
Physical Identification Guide
Step 1 — Front Panel Emblem
All authentic 75S-2 units carry the Winged Emblem. This is the single most important visual identifier when evaluating a claimed 75S-2.
Step 2 — Model Designation and Filter Count
Verify “75S-2” on the front panel and rear serial plate. A key identification feature of the 75S-2 is the presence of the 4.0 kHz bandwidth position on the filter selector — this is present on the 75S-2 but absent on the 75S-1. The 75S-3 has different filter options. Verify all filter positions are populated with original Collins Mechanical Filters.
Step 3 — Component Date Codes
Internal electrolytic capacitors carry YY WW date codes. For an authentic 75S-2, the latest original date codes should fall in the 1962–1965 window. Date codes beyond 1965 on original (unreplaced) components would be inconsistent with 75S-2 production dates.
Step 4 — Manual Edition
Original 75S-2 instruction books have copyright dates of 1962–1965 only. Confirm the manual covers the 75S-2 specifically — not the 75S-1 or 75S-3, which have different filter configurations.
Typical Restoration Considerations
| Component | Recommended Action | Notes for the Rare 75S-2 |
|---|---|---|
| Electrolytic Capacitors | Reform or replace — first priority | 60+ year old electrolytics. Given the unit’s rarity and value, consider full capacitor replacement with documented original-spec equivalents. |
| Power Supply Rectifiers | Replace with 1N4007 or equivalent | Original selenium rectifiers must be replaced. Document original configuration before removal. |
| Mechanical Filters (×4) | Test all four; confirm 4.0 kHz position is original 75S-2 filter | The 4.0 kHz filter is the 75S-2’s unique feature. Confirm it is a genuine Collins Mechanical Filter of appropriate type. Replacements may have been substituted from 75S-3 filter types — cross-reference part numbers with instruction book. |
| Tube Complement | Test all tubes; document original types | For a rare unit, original tube types have provenance value. Test before replacing; keep originals where serviceable. |
| PTO Alignment | Verify drift only; do not adjust unless out of spec | The permeability-tuned oscillator is a precision Collins assembly. Allow 30+ minute warm-up. Do not adjust if within specification. |
This guide consolidates publicly available CCA survey data, community restoration reports, and personal collection documentation. Serial number range estimates carry higher uncertainty for the 75S-2 than for any other S-Line receiver due to its low production volume. Contributions and corrections welcome via vk6ada.com.au or r-390a.net.
References, Citations & Credits
- Collins Radio Company. 75S-2 Receiver Instruction Book. Cedar Rapids Division, Cedar Rapids, Iowa. Various editions ~1962–1965. Archived by the CRA: collinsradio.org — Technical Archives
- Collins Radio Company. 75S-2 Receiver Instruction Book, final edition. CRA archive: collinsradio.org
- Blocksome, Rod K0DAS. “The Collins S-Line Logo and Emblem Transition History.” CCA Historical Archives. 2013–2016. collinsradio.org — Historical Archives
- Blocksome, Rod K0DAS. Collins S-Line Receiver Production Surveys. CCA Technical Archives. Various years. collinsradio.org — Blocksome Surveys
- Collins Radio Association. Collins Radio Technical Archives. collinsradio.org
- WA3KEY Virtual Collins Radio Museum. Collins S-Line Reference Pages. wa3key.com. Accessed 2026.
- QRZ Forums — threads documenting Collins 75S-2 rarity, serial numbers, and filter configurations. forums.qrz.com. Accessed 2026.
- Collins Collectors Association FAQ. WA3KEY: wa3key.com/ccafaq.html. Accessed 2026.
- Anonymous (attributed to a former Collins employee; reported by Roger KB4THL). “[Collins] Winged versus Round Emblems.” QTH.net Collins Reflector, July 2005. qth.net — July 2005
- QST Magazine — Collins Radio advertisement, 75S-2 Receiver, ARRL, ~1962. worldradiohistory.com
- Peace, Mike VK6ADA (Administrator). r-390a.net. r-390a.net.
- Peace, Mike VK6ADA. Collins 75S-2 Receiver (RARE) — Project Page. vk6ada.com.au. vk6ada.com.au/collins-75s-2-receiver-rare/. 2025–2026.