There is not a lot of MCN data available to draw firm conclusions but it appears as though the MCN numbers were only unique for a given top level part number. The system of assigning and even marking MCN numbers on the unit changed over time.
#Collins 51s 1 we serial number
Only after a manufactured unit has passed final test and quality control inspection is a serial number affixed to the radio. This is the Manufacturing Control Number and is used for configuration and revision control as the equipment progressed through the manufacturing process. On most receivers you will see an “MCN” followed by several digits. Production ran to about 1982, but no data has been found for units produced after 1979, so I’m estimating 500 units for 1980 and beyond.
#Collins 51s 1 we serial numbers
Other than this instance, the serial numbers are sequential without regard for specific type number until 1975 when different serial number blocks were used for unique 51S-1 types. In general the serial numbers were not purposely scrambled on the 51S-1 however, there are strong indications in the data that around 1975 some 124 51S-1’s were assigned early serial numbers that were likely used for other types (e.g. Note 2 – Very little data has been found for FY80 – 82.
Therefore FY1974 was 13 months long (1 Sep. until 1974 when it was changed to run from 1 Oct to 30 Sep. Note 1 – The Collins fiscal year ran from 1 Sep. Table 1 – Production Quantities of 51S-1 Receivers Fiscal Year 1 Tables 1 and 2 provide details resulting from my research into the production history of this fine radio. By the time production ended, some 12,136 51S-1 receivers came forth from the Collins factories by my count & estimates. But things started to roll in 1962 and continued for 20 years. The first production of the 51S-1 occurred in August 1961 when three units were completed just before the end of fiscal year 1961. There is a tuner shield with holes for alignment and a tube stage on the left.įigure 2 – 51S-1 Receivers – Prototype on the Left It has a five fluted Megacycle knob (Early production 51S-1 were the same and then it was changed to four flutes). The rear panel connections are different. The prototype cabinet is a modified KWM-2 cabinet (obvious from the rear). Under the hood things are similar but different in a few areas as shown in Figure 2 where the prototype on the left is placed beside a 1963 winged emblem production model for comparison. The meter switch is labeled “RF, Line 1, Line 2” (The prototype had two line audio outputs). The “Rejection Tuning” scale has expanded tic marks. The noise blanker knob is located where the production logo was later placed. The Collins logo is located above the phones jack.
The “Zero Set” knob is round like the S/Line instead of the small “bar” type used in production. In addition to the main tuning knob, a list of other changes includes: Arlo Meyer, W0LBK, told me they wanted the feel of a weighted knob for tuning but it was going to turn an extensive gear train. The main tuning knob is machined from solid brass and painted black. For example it has a noise blanker although the module was missing from the chassis. One can see several items that are much different than the production versions we are used to seeing. So I did some minor cleaning and then put it on display in the Rockwell Collins Museum. But after further thought, I decided it was really a historical artifact and shouldn’t be tampered with. I accepted of course and spent some time examining the unit, taking photographs, and even contemplating restoring it to operating condition. Several years back, an engineer from Ed’s 51S-1 team retired and asked me if I would be interested in the prototype 51S-1 receiver. Jerry Vonderheide, W0NGL, later created the 51S-1A – a version powered from 28 Vdc for aircraft operation. It was none other than Ed Andrade, W0DAN – The same fellow who earlier brought forth the Collins 51J-4 and the KWM-2! All three equipments were in production far longer than the average Collins HF equipment – a testimony to the solid design and outstanding performance achieved by Ed and his engineering team.
I would like to acknowledge the project engineer who led the design of the 51S-1 receiver.
#Collins 51s 1 we update
This article is an update – along with some additional information and insight added. I published the results on the reflector and, in the years since, I have continued to gather additional data from other sources. The project was designed to shed light on the many questions collectors had about production quantities, anomalies, scarcity, etc.
A number of years ago I conducted surveys of Collins ham equipment on the CCA reflector.
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