Lionel S.O.S. replacement?

The SOS circuit in the Hudsons counted the pulses

from the motor to control the on/off cycle for the steam

sound. There is a capacitor on the board that is too small

so some times you get only one chug for 2 revolutions of the

drive wheels. Changing the capacitor from 100 pf to .1 mf will

help the chugging sound. The capacitor is on the end of the

board and connected to one wirer wire of the three wires

connecting the engine to the tender.

It might be easier and less hassle/cost to just look for another tender.  I see S.o.S tenders on sale at swap meets and on e-bay sometimes and they go for very little because most people would rather have the railsounds, etc. 

These boards can be repaired. I know of a gentleman who can repair just about all of the Lionel Electronic Sound Of Steam Circuit Boards. I had a few repaired in the past. 

Email me for the contact info.

I had the same problem in the same engine. I ended up just removing the entire system and am contemplating installing a PW air whistle.

I always liked the S.O.S. in TM videos. It was very "80s" and captured that era pretty well. But in person, it is God-awfully shrill.....

Ah-ha! I suspected that was how they handled the timing on the motor-timed version. You saved me a bit of poking around with the meter if one of mine ever acts up.

Biggest problem with failed SOS boards I've seen is that there are multiple versions and revisions over the years; if you want to keep an MPC engine original, you have to find the same type -- just any SOS tender can't be a donor. If you're familiar with electronics, it can be quicker to repair them.

What do you guys put down between the board and the tender frame if the foam is no longer?

6008708085

Bill

Double sided foam tape.

A TrainSounds box works for me.  Also, i took a PE sound tender, removed shell, got a Western Depot UP shell, and run it behind my 726.  I just pretend it is 844......!

Lionel changed the count down frequency for the SOS board

used in the Hudson or the Southern 2-8-2. There were 2 different

pads that could be jumpered to allow about 1 chugg per wheel

revolution for either the Hudson or the 2-8-2. The motor in the Hudson

required more motor revolutions per wheel revolution than

the 2-8-2 so a different count down was used.

The best SOS was the the PRR turbine. The turbine would

chugg going forward but not in reverse. The motor pulses

would go thru the back up lights in the tender.

The boards were all the same.

The June 1993 issue of the LCCA "The Lion Roars"

has a drawing of the SOS board. The circuit to

operate the whistle does not require that the

center rail be more positive than the outside

rail.