5V Proto2 Engine failures

What condition are the batteries in????

Bruce, It depends, but the answer is usually no.  Much lower success rate on PS-2 5V once they fail.  It is best to give to an MTH tech who can test and repair at component level.  IF the board is dead, the best alternative is installing the PS-2 3V board with 5V connectors, change the speaker to 4 ohm and install the 2.4V battery and charging harness.  An upgrade sound file is installed and your engine is better than new, at least electronically.  I can do the work, if you don't have a tech in your area.  E-mail in profile.  G

One question, can they run in conventional?

I've fixed a couple of 5V boards that had total failures, but most are dead and they stay that way.  Individual lights or couplers being out is a different manner, those can usually be fixed.

I actually went through my little pile of 3V bad boards and rescued most of them, just got a couple that will probably never run again.  Those are much easier to fix.

John, send them to GGG.  He can fix anything but a broken heart.

If the 5V board will run in conventional it can somethimes be fixed with a hard reset.  I have got lucky with many.

Marty, the boards that I'm talking about have cooked diodes in the center of the stack.  They're impossible to reach in there.

Interesting idea about the hard reset, I presume you're talking conventional?  I have one 5V board that won't wake up in command, I could try a conventional reset on it, can't hurt.

John, Did you try a recover engine on the one that works conventionally but not in command? 

Actually, I found some jumper points so you can replace those internal diodes with external, the problem is that they are not always the cause of the problem.   G

Yep, Recover Engine is one of my basic tests when nothing else works.  Most of the ones I blame the internal diodes for you can actually see and smell the issue, not likely to be any doubt there's a problem there.

I'd be interested in where you located the external points.  That would also allow you to test the internal diodes.

I do have a couple that have no obvious flaws that still don't work, I haven't given up on them, just tinker with them when I get the urge.

The last several I have done, had a Capacitor blown apart in them, always the same cap on every board.

Usually, you'd think something would take the cap out.  Typically, a shorted diode will put AC on the caps and they'll pop like firecrackers.

The unanswered but essential question is why do the diodes fail?  Poor component type selection?

That's a question that only MTH can answer, the design of that board set is not documented for the world to see.

The question was essentially rhetorical.

There are a number of circuits those diodes feed that drive the board, charge the battery, etc...  Any of those circuit failures can cause the diodes to overload and fail.  I have restored a few where the diodes were the issue, but more often than not there was another short that overloaded the diodes.

I have never been lucky to just replace the cap, when cvap is blown something else was always shorted.  G