About a dozen posts up, the question of when CHEC ("Constant Horsepower Excitation Control") was introduced came up.
Data point.
I have the 1974 edition of the (Simmons-Boardman Publishing, published for or in collaboration with the AAR Mechanical division) "Car and Locomotive Cyclopedia," published (according to date on title page) in … 1974. This isn't quite a General Electric document, but… Chapters aren't signed, so it isn't clear who actually wrote various parts: Simmons-Boardman employees, AAR committee members, or manufacturer staff are all in principle possible. However, it LOOKS to me as if the information in the technical chapters was PROBABLY provided by the manufacturers: the descriptions of GE, EMD and MLW engines and control systems differ enough in format and organization that I think the final writer must have been essentially cutting and pasting material provided by the three manufactures. SO: for the moment I am tempted to think the Cyc should be accorded "almost official" status.
Punch line. The half-page description of CHEC (page S17-2, near the beginning of the section on GE control systems) says that General Electric locomotives with AC transmissions have CHEC. No suggestion that it is an option, or that it is something that is about to be introduced, just a blanket statement. So I think a cautious, minimum, guess is that any U-series GE unit with AC/DC transmission built in 1975 or later had a CHEC engine, and that it is likely that CHEC became standard a bit earlier: 1974 maybe.
What units would this cover? (Many late U23B had AC transmission, but for the moment I'll limit myself to models with 16 cylinder engines.) The last U33C (for Southern Pacific) and U36B (the units ordered by Auto Train and a few years later delivered to Conrail) were built in 1974: so, maybe-maybe-not. Units built in or after 1975 include (i) Amtrak's P30CH, (ii) the last five U30B (for SLSF), (iii) a few late U30C for BN, (iv) a large number of U30C (two orders, one in 1975 and one in 1976) for UP, and (v) some U36C for ATSF and NdeM (both railroads had sizeable orders built partly in 1974 and partly in 1975). (Tally from roster at the mack of Greg McDonnell's "The U-Boats.")
(Pretty puny piece of information compared to Will's posts, but the best I could do!)
Data point.
I have the 1974 edition of the (Simmons-Boardman Publishing, published for or in collaboration with the AAR Mechanical division) "Car and Locomotive Cyclopedia," published (according to date on title page) in … 1974. This isn't quite a General Electric document, but… Chapters aren't signed, so it isn't clear who actually wrote various parts: Simmons-Boardman employees, AAR committee members, or manufacturer staff are all in principle possible. However, it LOOKS to me as if the information in the technical chapters was PROBABLY provided by the manufacturers: the descriptions of GE, EMD and MLW engines and control systems differ enough in format and organization that I think the final writer must have been essentially cutting and pasting material provided by the three manufactures. SO: for the moment I am tempted to think the Cyc should be accorded "almost official" status.
Punch line. The half-page description of CHEC (page S17-2, near the beginning of the section on GE control systems) says that General Electric locomotives with AC transmissions have CHEC. No suggestion that it is an option, or that it is something that is about to be introduced, just a blanket statement. So I think a cautious, minimum, guess is that any U-series GE unit with AC/DC transmission built in 1975 or later had a CHEC engine, and that it is likely that CHEC became standard a bit earlier: 1974 maybe.
What units would this cover? (Many late U23B had AC transmission, but for the moment I'll limit myself to models with 16 cylinder engines.) The last U33C (for Southern Pacific) and U36B (the units ordered by Auto Train and a few years later delivered to Conrail) were built in 1974: so, maybe-maybe-not. Units built in or after 1975 include (i) Amtrak's P30CH, (ii) the last five U30B (for SLSF), (iii) a few late U30C for BN, (iv) a large number of U30C (two orders, one in 1975 and one in 1976) for UP, and (v) some U36C for ATSF and NdeM (both railroads had sizeable orders built partly in 1974 and partly in 1975). (Tally from roster at the mack of Greg McDonnell's "The U-Boats.")
(Pretty puny piece of information compared to Will's posts, but the best I could do!)