Collins 30L-1 Serial Number Guide – VK6ADA

Collins 30L-1 — Serial Number & Production Guide

VK6ADA Technical Reference · Collins S-Line Vintage Amateur Equipment · March 2026 · Mike Peace VK6ADA

The Collins 30L-1 RF Linear Amplifier was produced from 1961 through the mid-1970s at the Cedar Rapids, Iowa facility.^[1] This reference guide consolidates serial number ranges, emblem transitions, manual edition history, and known circuit variations to help collectors and restorers authenticate and date their units.

Overview & Specifications

The 30L-1 was designed by Gene Senti, W0ROW^[8] — the same engineer responsible for the KWM-2 transceiver and the commercial KWS-1 transmitter. Introduced in 1961 at a list price of $500 USD (as advertised in QST),^[10] it became the standard companion linear amplifier for the Collins S-Line station. Four 811A triode tubes drive a broadband pi-network output, covering the five principal HF amateur bands.^[1]

Manufacturer

Collins Radio Company — Cedar Rapids Division, Cedar Rapids, Iowa

Model Number

30L-1 (Collins type designation: RF Linear Amplifier)

Production Period

1961 – approximately 1975–1976

Power Tubes

4 × 811A triode (572B approved as direct replacement)

Power Input (max)

1,000 W PEP SSB / 1,000 W CW

Frequency Coverage

3.4 – 30.0 MHz — Amateur bands 80, 40, 20, 15, 10 metres

Harmonic Suppression

All harmonics ≥ 50 dB below output signal

Mains Supply

115 V AC (primaries parallel) or 230 V AC (primaries series), 60 Hz single-phase

Modes

SSB (USB / LSB), CW, AM

Cooling

Forced-air fan, 115 V AC, 60 Hz, single-phase

Introduced Price

$500 USD (QST, 1961)^[10]

Designer

Gene Senti, W0ROW — Collins Radio Cedar Rapids Engineering^[8]

Important Note on Serial Number Sequencing

⚠ Random Serial Number Assignment — Collins S-Line Policy
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 — a policy designed to prevent price discrimination among model variants sharing the same chassis. As a result, a lower serial number does not necessarily indicate an earlier production date. However, broad ranges — especially in relation to emblem type — do correlate meaningfully with production eras.

The emblem type on the front panel is the most reliable single dating indicator for a 30L-1. Serial number ranges serve as secondary corroborating evidence, particularly when cross-referenced with component date codes inside the chassis.^[3]

Collins Logo / Emblem Production Eras

Collins Radio used several distinct front-panel badge emblems across the production life of the 30L-1. The emblem is located at the lower-right of the front panel and is one of the most useful quick-identification markers for the collector.^[3]

Winged Emblem 1961–1969

Trans.

Small Round Emblem

Large Round

1961196619701973

Emblem Type	Production Period	Approx. S/N Range	Physical Description	Collector Notes
Winged Winged Emblem	1961 – Fall 1969^[3]	~1 – ~28,000 (approximate upper boundary)	Classic silver-and-blue winged Collins insignia. Two mounting holes visible on either side if badge replaced. Most desirable to collectors.	Majority of surviving 30L-1 units. KWM-1 interface wiring varies by KWM-1 S/N above or below 861.^[1]
RE Trans Round Emblem Transition	Fall 1969 only^[3]	~27,000 – ~30,000 (overlap zone)	Round “meatball” Collins emblem plus two small grey screws either side plugging former winged-emblem holes. Immediately identifiable.	Least common variant. The grey screws avoided scrapping front panels already on the factory floor when the new emblem policy was issued.^[3]
Small RE Small Round Emblem	Fall 1969 – ~1975^[3]	~28,000 – ~38,000 (approximate)	Circular Collins emblem approximately dime-sized (~18 mm diameter). No flanking screw holes. Single central attachment point.	Post-Rockwell acquisition era. Circuit design essentially unchanged from late Winged Emblem production.
Large RE Large Round Emblem	~1974 – FY1976^[3]	~36,000 – ~43,000+ (approximate)	Round Collins emblem approximately nickel-sized (~21 mm diameter). Slightly bolder typeface on the emblem.	Late-production. S/N 41,728 documented as a late Large Round Emblem unit.^[7]

Note: S/N range boundaries above are derived from the CCA 30L-1 Production Survey by Rod Blocksome K0DAS,^[4] documented sales, and component date-code analysis by the collector community. They are best-estimate ranges, not definitive cut-offs. Cross-referencing component date codes with the serial number is the most reliable dating method.

Serial Number Lookup Reference

Quick Era Identifier — Enter Your Serial Number

⚠ Estimates only — individual serial numbers were issued in random order per Collins S-Line policy.^[9] Always verify with physical emblem inspection and internal component date codes.

Documented Serial Number Data Points

The following table lists serial numbers from known, physically inspected units. This corpus forms the basis for the era range estimates above.^[4]

Serial Number	Emblem / Era	Notable Features	Source / Reference
10,798	Winged	Confirmed Winged Emblem unit; excellent cosmetic condition.	ke9pq.com — documented equipment sale
12,500	Winged	Winged Emblem; 120 VAC wiring. Long-term storage; HV capacitor replacement required.	ke9pq.com — documented equipment sale^[6]
13,954	Winged	Owner-reported S/N; consistent with Winged Emblem period c.1963–1965.	QRZ Forums — WA4RTE^[7]
27,366	RE Trans Military	Round Emblem unit, military-origin rear-panel label. Internal resistor date-coded 1968 Week 22. Missing plate caps and parasitic suppressors at inspection.	EB5AGV Workbench — José V. Gavila Alcalá EB5AGV^[5]
41,728	Large RE	Documented “late serial number” Large Round Emblem unit in excellent condition.	ke9pq.com — documented equipment sale^[7]

Manual Edition History

Collins published multiple instruction book editions for the 30L-1 throughout its production life. The manual edition in your documentation package can help corroborate the approximate production era.^[1],[2]

Edition	Date	Collins Part Number	Copyright Years	Notes
1st Edition	1961	—	© 1961	Original publication with initial production units.^[10]
~2nd–6th Editions	1961–1964	Various	© 1961, 1962, 1964	Progressive service bulletin amendments. Archived at worldradiohistory.com.
7th Edition	15 February 1965	523-0122000-007311	© 1961, 1962, 1964, 1965	Comprehensive revision incorporating all service letter amendments to that date. Archive: CRA PDF.^[1]
8th Edition	Post-1965	—	© 1961–1966+	Final known major edition. Archive: CRA PDF.^[2]

Circuit Variations by Production Era

The 30L-1 underwent documented circuit changes during its production run, primarily communicated via Collins Service Bulletins and incorporated into subsequent manual editions.^[1],[2]

Known Factory-Incorporated Changes

Change Description	Component(s) Affected	Nature of Change	Era Indicator
Input circuit capacitor addition	C8, C12 (same as C3); R6, R13	Added to parts list and Fig. 7-1 schematic. Improves input SWR at band edges.^[1]	Mid-production; 7th Ed. service notes
Plate bleeder resistor change	R1; C11 deleted	R1 changed to 4,700 Ω; C11 removed from circuit.^[1]	Mid-production; 7th Ed. schematics
F1 fuse terminal change	F1	Reconnected to Terminal 4 on PSU board. See Fig. 7-1 revised connection notes.^[1]	Late Winged / early Round Emblem era
Rectifier diode specification	CR1–CR16	All specified as 1N4007 equivalents per assembly 1492. Improves HV supply reliability.^[1]	Progressive; many field-repaired units show this regardless of era
572B tube approval as 811A replacement	V1–V4 (power tubes)	572B approved as direct pin-for-pin replacement. Optimise Bias Adjust (R16) to 50 mA idling plate current after substitution.^[1]	All eras; 572B is the current recommended tube
C72 substitution for C12/C13	C12, C13 → C72	In later schematics C12/C13 references superseded by single C72. Where manual cites C12 and C13, substitute C72.^[1]	7th Ed. errata; mid and late production

KWM-1 Compatibility by Serial Number

The 30L-1 instruction book specifies different cabling depending on the paired KWM-1 exciter’s serial number — the only case where an exciter serial number governs 30L-1 installation.^[1]

KWM-1 Serial Number	30L-1 Cabling Procedure	Manual Reference
861 and above	Standard interconnection per Figure 1-3 main diagram.	§ 1.3.3 — KWM-1 S/N Above 861^[1]
Below 861	Alternative scheme; Note 4 and Detail A apply. Green wire to ground. Different ANT RELAY connection.	§ 1.3.4 — KWM-1 S/N Below 861; Fig. 1-3 Note 4^[1]

Note: This cabling distinction does not affect the 30L-1’s serial number or production era. KWM-2/2A and S-Line exciters (75S-x / 32S-x) are unaffected and use standard cabling throughout.

Physical Identification Guide

A systematic approach to dating and authenticating a 30L-1 from physical inspection, in priority order of reliability:

Step 1 — Front Panel Emblem

Winged Emblem: 1961–Fall 1969.^[3] Two screw holes may flank the position if the badge was replaced.
Round Emblem with flanking grey screws: Transition unit, Fall 1969 only. Extremely rare.^[3]
Small Round Emblem (dime-sized, ~18 mm): Post-Fall 1969 to approximately 1975.^[3]
Large Round Emblem (nickel-sized, ~21 mm): Mid-1970s through FY1976.^[3]

Step 2 — Serial Number Plate

Located on the rear panel. Plain integer format — no alphabetic prefix or suffix.
Cross-reference with range tables above. Random assignment means overlap is possible.^[9]
~1 – ~10,000: early production Winged Emblem era (1961–1963).
~10,000 – ~28,000: mid production Winged Emblem era (1963–1969).
~28,000 – ~43,000+: Round Emblem era (Fall 1969–1976).

Step 3 — Internal Component Date Codes

Electrolytic capacitors carry a two-digit date code in format YY WW (year / week of manufacture).
Resistors and film capacitors often carry similar date codes.
The latest date code on original components establishes the earliest possible ship date.
Example: S/N 27,366 contained a power resistor date-coded 1968 Week 22, placing manufacture no earlier than May 1968.^[5]
Replacement components post-date original production and should not be used for dating.

Step 4 — Manual Edition Check

Examine the copyright page of any original accompanying instruction book.^[1],[2]
7th Edition (15 February 1965, P/N 523-0122000-007311) is the most commonly encountered archived edition.
Copyright dates extending to 1966+ indicate a later-production unit or a replacement manual.

Step 5 — Military vs. Commercial Origin

Some 30L-1 units were procured by the US military (as with S/N 27,366, which carried a military rear-panel label).^[5]
Military-contract units may show additional serialisation plates or wiring modifications on the rear panel.
Military procurement does not alter the 30L-1 circuit design in documented cases; the front-panel emblem sequence still applies.
Military units typically command lower collector premiums due to occasional modifications and cosmetic differences.

Typical Restoration Considerations by Era

Component	All Eras — Recommended Action	Early Winged Era Notes	Round Emblem Era Notes
HV Filter Capacitors	Replace or reform as first priority. The most common failure on stored units. Aftermarket PSU board kits available.	Original large-can electrolytics. Reform carefully; replace if older than 40 years.	Same recommendation; later caps may differ physically.
Rectifier Diodes (CR1–CR16)	Replace with 1N4007 or equivalent. Original selenium or early silicon types are failure-prone.^[1]	May have original selenium rectifiers — replace without exception.	Likely already silicon from factory; verify.
Power Tubes (V1–V4)	572B is the modern standard for 811A. Set bias to 50 mA idling plate current after substitution.^[1]	Original 811A may be present; test before replacing.	Mix of 811A and 572B often found; standardise to one type.
Plate Caps & Parasitic Suppressors	Often missing from stored units. Required for safe operation. Reproduction and NOS parts available via Collins community suppliers.^[5]	Same design as later units.	Check for heat damage on suppressors.
Cooling Fan	Original fan: 115 V AC, 60 Hz. Test bearing operation. Replacement modern fans can be adapted.^[1]	Bearing grease may have dried; re-lubricate or replace.	Same recommendation.
Meter Glass	Frequently cracked or scratched. Reproductions available. Meter movement usually intact.^[5]	Winged-era meters cosmetically identical to Round-era meters.	Same as above.

This guide consolidates publicly available CCA survey data, community restoration reports, and documented sale records. Serial number range estimates should be treated as approximations. Contributions and corrections are welcome via vk6ada.com.au or through the Collins community at r-390a.net. Always cross-reference physical inspection with documented data before drawing conclusions about production date.

References, Citations & Credits

Collins Radio Company. 30L-1 RF Linear Amplifier Instruction Book, 7th Edition. Cedar Rapids Division, Cedar Rapids, Iowa. Part No. 523-0122000-007311. 15 February 1965. Copyright © 1961, 1962, 1964, 1965 Collins Radio Company. Archived by the Collins Radio Association (CRA): collinsradio.org — 30L-1 7th Edition Manual (PDF)
Collins Radio Company. 30L-1 RF Linear Amplifier Instruction Book, 8th Edition. Cedar Rapids Division, Cedar Rapids, Iowa. Post-1965. Archived by the Collins Radio Association (CRA): collinsradio.org — 30L-1 8th Edition Manual (PDF)
Blocksome, Rod K0DAS. “The Collins 51S-1 HF Receiver — Logo and Emblem Transition History.” Collins Collectors Association (CCA) Historical Archives. 2013–2016. Documents the Winged Emblem (1961–Fall 1969), Round Emblem Transition (Fall 1969), Small Round Emblem (~1969–1975), and Large Round Emblem (~1974–FY1976) chronology — applicable across all S-Line and amateur Collins products including the 30L-1. collinsradio.org — 51S-1 Emblem History
Blocksome, Rod K0DAS. Collins 30L-1 Production Survey 2014. Collins Collectors Association (CCA) Technical Archives. 2014. Survey of serial number data, production quantities, and design change chronology for the 30L-1 amplifier. collinsradio.org — 30L-1 Survey 2014 (PDF) — See also: Rod Blocksome’s full Collins Surveys index: collinsradio.org — Blocksome Surveys
Gavila Alcalá, José Vicente EB5AGV. “EB5AGV’s Workbench: Collins 30L-1 Restoration.” Personal technical restoration log documenting S/N 27,366 — a Round Emblem unit of military origin. Key finding: internal power resistor date-coded 1968 Week 22, establishing a minimum manufacture date of May 1968. Unit missing plate caps and parasitic suppressors at time of inspection. Accessed 2026. jvgavila.com/30l1.htm
KE9PQ Ham Radio Equipment Sales. Collins 30L-1 Winged Emblem HF Linear Amplifier — S/N 12,500 and S/N 10,798 (documented listings). Accessed 2026. ke9pq.com
Multiple QRZ / community sources documenting specific serial numbers:
• WA4RTE — QRZ Forums thread: “Collins 30L-1 Date of Manufacture” (S/N 13,954). forums.qrz.com — WA4RTE thread 2019.
• S/N 41,728 documented as a late Large Round Emblem unit: ke9pq.com — documented equipment sale Accessed 2026.
Collins Collectors Association. The Collins Collectors Association FAQ. Credits and biographical notes on Collins Radio engineers:
• Gene Senti, W0ROW — Designer of the KWM-2, 30L-1, and KWS-1 (and head of the engineering group covering both HF commercial and amateur products).
• Warren Bruene, W5OLY — Designer of the 30S-1 linear amplifier and 30K-1 transmitter; Collins’ most-tenured employee, retired 1984.
• Dennis Day — Prime engineer on the 75S-3 receiver series.
Hosted by the WA3KEY Virtual Collins Radio Museum WA3KEY: wa3key.com — CCA FAQ Accessed 2026.
Anonymous (attributed to a former Collins employee; reported by Roger KB4THL). “[Collins] Winged versus Round Emblems” — QTH.net Collins Reflector, July 2005. Documents that Art Collins decreed S-Line serial numbers to be issued in random (non-sequential) order to prevent price discrimination among model variants sharing the same chassis. The policy was confirmed as of c.1963–1964. qth.net/pipermail/collins — July 2005
QST Magazine — Collins Radio advertisement, 30L-1 RF Linear Amplifier, introductory price $500 USD. American Radio Relay League (ARRL). 1961. QST archive (1915–1969): worldradiohistory.com — QST Archive
Collins Radio Association (CRA). Collins Radio Technical Archives — Manuals, Service Bulletins, and Historical Articles. Comprehensive archive of Collins Radio documentation, including all 30L-1 manual editions. collinsradio.org — Technical Archives Accessed 2026.
WA3KEY Virtual Collins Radio Museum WA3KEY. Collins 30L-1 Reference Pages. Comprehensive community reference including Gene Senti history, circuit documentation, and collector resources. wa3key.com/30l1.html Accessed 2026.
Peace, Mike VK6ADA. Collins 30L-1 Amplifier Project — vk6ada.com.au. Personal project documentation, restoration notes, and S-Line station reference. vk6ada.com.au/collins-30l-1-amplifier-project/ 2025–2026.
Peace, Mike VK6ADA (Administrator). r-390a.net — R-390A/URR Frequently Asked Questions and Collins Community Knowledge Base. Peer-reviewed community resource for R-390A and Collins radio restoration, parts, service, and technical documentation. r-390a.net Administered 2010–present.