Re: {Collins} Serial # Range - 75S-3B SB1?

?Would sure be interested in the "instructions" issued by Mr. Collins with regard to S-Line SN scrambling. I talked to one of the configuration management guys from the S-Line era and he denies there was any scrambling. I have also talked to several engineers and techs involved with the S-Line and they were not aware of intentional scrambling.

Everyone agrees that the serial number discontinuity is likely a result of the fact that blocks of serial numbers were issued on individual contracts. Rod Blocksome and I looked at some of the old micro film records several years ago and had hoped to establish a good data base for S/Ns vs delivery dates, but before we able to complete the project, the records got moved to "secure storage" at an off site location. We could still access the records, but we needed to provide a "business case" and provide charge center numbers for the fairly significant costs associated with getting the records. Both of us were extremely busy with our "day" jobs at RC, so we had to abandon the project.

An interesting aspect of the project revealed that there were many SN 1s ( as well as 101s and1001s). When I talked to the nameplate issuers, they said if the customer was military/govt, the nameplate would have included the contract information and the SN was issued against the contract. I don't think any of the commercial contracts had the contract number on the nameplate, therefore the requirement for the serial number blocks.

Another thing to consider is that there were a fairly large number of "dash" numbers. The KWM-2 had 7 or 8 dash numbers, so each dash would require a new SN sequence. (Most of the dash number differences were related to nameplate requirements).

The other thing to consider is the MCN system (Manufacturing Control Number). I think it was introduced sometime during S-line Production, but I have never been able to absolutely determine when. This number is a better indication of build sequence for a particular assembly. This allows building common assemblies and conducting unique contract required testing before the final serial number nameplate is installed.

The other thing that may have impacted SN sequencing is that some units had to be reworked or repaired after serial numbers were applied. I don't think the delays were generally enough to a be a factor, but I understand there were a few units that got shelved for up to a year before they made it back through testing.

Interesting stuff.

Jim w0nkn

From: "Glen Zook" <gzook@xxxxxxxxx>
Sent: Thursday, June 02, 2011 12:22 AM
To: <collins@xxxxxxxxxxxxx>; "Rich Hallman - N7TR" <rich@xxxxxxxx>
Subject: Re: {Collins} Serial # Range - 75S-3B SB1?

At the instructions of Art Collins the serial numbers were "scrambled" and therefore you can't tell from the serial number the date of production. This was because the 75A-4 receivers were valued depending on the serial number. There are ways of estimating the date of the receiver including the dates on the heterodyne oscillator crystals (if they have not all been changed). Typically, the crystals were used within a month, or two, of the date which they were made.

Glen, K9STH


--- On Wed, 6/1/11, Rich Hallman - N7TR <rich@xxxxxxxx> wrote:

Is there a serial number range that all 75S-3B's had the SB1 / 2 included from the factory?

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