RS-3 versionsUsing information from a number of places, I believe that as of December 2007, there are approximately 5 versions of this loco. (if you have corrections to this information, please let me know)Version 1:Introduced in early 1997. George Schreyer has a receipt for his in February.The first version has the axles going into bearings in the journals in the sideframes, and these are sprung. The bearings are normal brass sleeve bearings, not ball bearings. There is an adjustment screw on one end of each power block to adjust gear lash.(looks like both ends.... need to check with George) (Picture courtesy of George Schreyer)Inside, the wiring seems to be pretty much point to point; wires from the trucks go to a small square board on the chassis, and then up to the switch board in the shell.Version 2:There is a second version that looks identical externally to Version 1, but internally the power trucks were changed; there is no gear lash adjustment screw on the pivoting axle. (Picture courtesy of George Schreyer)More significantly, the wiring was changed; the motor blocks now plug a long circuit board on the chassis. They plug in from the bottom and there is a 2 pin and a 3 pin connector (one from track pickups, one from the motors). The external spotting feature is that the cover to the switch compartment now has small lips molded into it to make it easier to remove.There is now a small daughter board on the switch circuit board that has a voltage regulator, using a Motorola 8 pin IC. This is to give full light intensity at lower voltages.Version 3:The third version has the "new" ball bearing power trucks. These trucks can handle more weight without premature wear. Even though not sprung, they seem to be better running. As far as I can tell, they did not come with the weight pre-installed in the fuel tank. Somewhere in this production run, the MU cables were added. The axles no longer ride in the journals, even though the journals are still sprung and look identical from the side.The regulator circuit on the daughter board uses the now familiar PIC processor (it has a lot more pins) that is used as a voltage regulator on many current Aristo diesels.Version 4:This version came with new internal wiring, significantly the Aristo standard socket. MU cables were also found at the ends of the loco. There is a new style smoke generator. The fuel tank weight is pre-installed. The fan grill is an etched metal piece, and the handrails are formed differently.Note: in this version the components on the chassis are reversed end to end, so while the DC "shorting" plug will fit, adding ANY decoder to the Aristo socket will interfere with the speaker. The components on the chassis need to be removed and reversed end to end and will require lengthening of one set of wires from the main board to the small boards at each end of the chassis.Version 5:This version came out in late 2007, and it has the internal assembly (boards and weight plates) on the chassis reversed from version 4. This means that plugging in an Aristo onboard TE (Train Engineer) receiver or QSI decoder (see the DCC section for more on QSI) will no longer hit the speaker. I have found no other differences.Version 6:Not sure of the date or reason, but the insides are assembled backwards again! Come on guys!Other notes:Some of the first RS-3's in the new power block style had traction tires. This was for just a few years, and all traction tires were eliminated about 1998 - 2000.At some point Aristo upgraded the speaker from a small magnet to a large one. If the speaker magnet is almost as wide as the speaker frame, then you have the upgraded speaker. I have been told the upgraded speaker is also water resistant, but I can tell you it is not! I left my RS-3 out when my sprinklers went off and it ruined the speaker.I believe the speaker change happened pretty early in the production. If you have the original one, it may distort if you have a quality sound system.There was at one time an optional sound system by PH hobbies. I do not know which versions this was available for, but most of the existing ones are dead by now; it was Aristo part number ART-29338. It had prime mover sounds, horn, bell, and "cab chatter". The last 3 are triggered independently by reed switches and magnets. It lived in the fuel tank, subsequent versions have weights inside.See George Schreyer's site for more detailed information.