Is it safe to assume if you have an electronic E unit with 2 heat sink tab style transistors, and one that is identical with 4, the one with 4 will run two motors? I have the Lionel reverse engineered solid state E unit schematic and parts list, but it does not say anything about the number of motors. I also saw an ad for one with 4 transistors and the ad called it a '4 motor' E unit. Anything obvious to the casual observer when it comes to guessing motor capacity?
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Not at all, usually the difference is one may be a half-wave motor drive. The real way to judge the motor drive capability is by their amperage ratings.
Thanks John, but there was no spec given, and the TIP 31 and 32 transistors feeding the motor have a 3 amp continuous current rating, so at first blush it would seem a single pair would be in the 3 amp range, and doubling them up would mean maybe 6 amps. I will have to investigate further and see if the higher current units use something other than TIP 31's and 32's.
You have to read the fine print. The TIP31/32 only have a 3 amp rating when they're properly heatsinked! Any of these transistors will only handle a fraction of their maximum ratings with no heatsink.
Also, they're probably configured in a H-Bridge so that each transistor carries the full load of the motor. In the circuit below, Q1 and Q3 are turned on to run in one direction, and Q2 and Q4 are turned on to run in the other direction. For speed control, typically they would have a PWM input signal on the A or B inputs to modulate the power to the motor.
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