Will running Proto 3 Loco with incompatible transformer hurt?

I don’t know if it will hurt but I would just buy the correct power source. The sound is telling you it’s not happy.

I would avoid any of the pre and post war Lionel power sources.  They are too prone for power spikes which blow up boards.  Ask me how I know!

However I agree that if you are having issues, the correct power source is the best bet.  For MTH, sine wave AC output is the best.  Lionel and the smaller MTH transformers have a chopped wave output the can cause issues.  Not necessarily permanent damage, but just challenges.  For AC I rely on the MTH Z-4000, but the old ROW AC transformers are great.  MRC makes some good quality AC transformers coming out of the HO market that they dominated since the 60's.

@GG1 4877 posted:

I would avoid any of the pre and post war Lionel power sources.  They are too prone for power spikes which blow up boards.  Ask me how I know!

Why are they more prone to spikes than a newer one?

Is this a DC power supply?

Yes, DC.

As rod says, it is not on the list but that noise to me sounds like lubrication. Can you put it in a cradle upside   down and run it? This thread is like the old click and clack radio shows!

@John H posted:

Why are they more prone to spikes than a newer one?

The main issue is just improved technology in managing AC power output.  Alternating Current is based on the concept of introducing a sine wave to the power to create momentum.  AC does vary in voltage.  A good example is that a traditional 120V outlet actually varies from around 110V-130V at any given time.  A modern transformer just regulates the voltage variation better.  Also the fuses trip faster in modern transformers due to sensitive electronics. 

Maybe I'm figuring it wrong, but a 20 volt AC variation would amount to about a 4 volt variation on the secondary side, hardly a high voltage spike. If breaker speed is a problem, that could be remedied with adding a fast one to an old transformer. Besides, adding a TVS is the recommended solution for spikes, and transformers don't have them.

John,

You are correct that a TVS is the ideal way to go.  That does alleviate most issues.  Best practice that many new to the hobby may not be aware of.