MPC transformers and steam sounds questions

Both the 4125 in red or blue are 25 watt….

besides the mighty sounds of static, Lionel did use the old rocks in a tumbler method to make a pseudo chuff sound,…..nothing elaborate, just a rotating drum that rode on the center rail and beads tumbled around inside to make a sound …..

Pat

Mike D, yes Lionel MPC did have a very rudimentary sound system they utilized all the way up to at least 1987.  It consisted of a round container fitted underneath the tender body which would come into contact with the middle rail.  It was covered with a rubber like substance which would aid it in turning as the train ran across the middle rail.  The round container was filled with BB like metal balls which was supposed to simulate a Choo Choo sound as it turned while the train was running.   It was strictly a mechanical device and not electrical.  My daughter-in-law's mother gifted me her late husband's train which has this device.  It is listed as the MOPAR Express and has a 4-4-2 Atlantic type die cast engine for its motive power and three or four freight cars.  The outfit was manufactured in 1987.  I only ran it once and then packed it away.  Believe me when I say the "sound system", if you want to call it that , was quite rudimentary.  Curiously, there was not one word to be found in the operating instruction pamphlet about this sound system.  

Also, the set came with an oval of 027 track and a red 25 watt transformer.

One more note... there was a blue transformer with a metal handle, number 4150 I believe, which was rated for 50 watts.  One of the terminals could be pressed down to interrupt the circuit for direction changes.  It came in the better sets with die-cast locomotives, so if you're trying to be period-correct that's something to think about.  I'm not sure how beefed-up it is "under the hood" to handle twice the wattage.  I grew up an MPC kid, but the year I got my first metal steam loco, I moved up to a postwar 1033 and never looked back.

I agree with what everyone has posted.  The "round thing" your friend describes is probably Lionel's "Mechanical Sound of Steam" which is a hollow rolling drum filled with pellets.  That being said, there were a at least a few different versions of the Electronic Mighty Sound of Steam. Notably, there was an early version with Whistle.  Then EMSoS went back to chuff only until 1980, when they introduced a different electronic whistle.  During this time there were changes to the circuit itself.  The earliest ones used only discrete components: transistors, resistors, etc.  At some point toward the late '70s (I'm not sure when) they introduced an integrated circuit.  IMO, the early versions without whistle have the "cleanest" sound, which is actually static or "white noise."

Also, there are two methods of modulating the "chuff."  One is with a pair of contacts on the smoke generator.  That method was used throughout the 1970s.  Beginning with the UP 8002 in 1980, the balance of Lionel's Collector steam locos relied on a hall effect wheel on the tender truck to control the chuff rate.  I guess this made the wiring easier, but the chuff was no longer guaranteed to sync with the movement of the crosshead.

If you get a loco with EMSoS, please remove the tender shell and re-mount the board with double-sided tape.  The foam pad used at the factory generally disintegrates after 50(!) years.  If the electronic board shorts to the tender frame (which is grounded), it can ruin the board and kill the chuff.  My $.02.