howdy!! i have a super old truck that we use as a shop vehicle, moving things around and such. it was being driven, all was fine. it was parked, now it wont drive forward and back. jacked the drive wheel up to find the motor IS turning, just real slow. checked the brakes, made sure they arent bound up. all is well. put 8 new brushes in the motor. no change. new Pot. doesn't make any difference. also, the M-speed contactor isn't closing. if i manually close the contactor, it winds up the drive motor for a split second, simultaneously kicks the forward or reverse contactor open, and opens itself (the M-Speed contactor). i've disconnected the field and armature points and taped them off to guage the operation of the system, minus the load of the motor, hoping it would isolate something, but it didn't. maybe i'm missing it.

Last thing, i don't have a full service manual for it. there is nothing about *how* to check the SCR's, just troubleshooting paths telling me i *should* check the SCR's. i've been at it for two days now, and i'm at my wit's end. please help!!

Model: 20-R30TN
Serial: 020-R30TN-7137S

thank you for your time!!