U-boat memories! Sweet! They had a very unusual glitchy OLD school transistor. For old heads that remember early electronics. The Generator field was controlled by a single transistor of the old can type, About a 3'4 in sized thing. The neat thing about these is that when they fail, they short circuit. What that does then is it applies maximum field to the generator! This, of course, can cause issues! My first experience with that particular problem was rather exciting! I had just fired up a unit we had rebuilt, and set it to do a "1 and 1." That is a stall check, powered up in notch one against full independent brake application. It should yield 300 amps and no movement. However, on this unit, I made sure the brakes were set, and handbrake, and wedges. Then fired it up, checked various voltages and charging rates, then climbed in the seat and set up for the "1 and 1" test. Put her in notch one and watched the ammeter peg at over 2000 amps!!!! She lurched over the wedges and moved about 6 feet towards the shop door before I could put it back in idle! Talk about pucker!!! My foreman stepped over to the floor beside my cab and had this grin on his face that said a lot! He was an old GE guy and knew exactly what to swap out, so I swapped out the FC card and tried again, same thing! Tried a third used card and proceeded to respond normally. WOW!!! To be fair, after I got outside with the unit, I tried this a few more times and discovered that the locomotives Load Regulator did it's job and ran the field signal down to 300 amps, after moving 8 - 12 feet down the track! The load regulator Is a hydraulic device that drops the electrical load to match the diesels rpm. To say that the dash 7 was a step up from these knuckle breakers is saying a LOT!