3 year old Lionel 4-4-2 (road number 8632) that will not run on antique track. Does anyone have any insight into whether this locomotive needs a digital power source or if it would have an issue running on a regular Lionel transformer?

AC or DC isn't the actual problem here. The locomotive is three years old and the transformer, also a Lionel, is only about 2 or 3 years older. Of six locomotives, only one is exhibiting this behavior.

There's a circuit board on the inside of the locomotive that has triacs, diodes, resistors, transistors, and an IC on it that looks to be the issue, if not a solid symptom of the root cause. (The triacs are overheating)

If this were HO or N scale, I would suspect a DC / DCC problem, but I'm unaware of any Lionels that require the use of a DCC-like transformer. Do those exist? AC or DC isn't the actual problem here. The locomotive is three years old and the transformer, also a Lionel, is only about 2 or 3 years older. Of six locomotives, only one is exhibiting this behavior. There's a circuit board on the inside of the locomotive that has triacs, diodes, resistors, transistors, and an IC on it that looks to be the issue, if not a solid symptom of the root cause. (The triacs are overheating) If this were HO or N scale, I would suspect a DC / DCC problem, but I'm unaware of any Lionels that require the use of a DCC-like transformer. Do those exist?

it may be the IC or some diodes but if you have a mulitmeter check the resistance of the resistors test the diodes and then if those check out then it ma be some contact issues it may be the IC or some diodes but if you have a mulitmeter check the resistance of the resistors test the diodes and then if those check out then it ma be some contact issues