Is this PS2 3v board repairable? - Fixed

Sent you an email Bob, hopefully that will help you.

@H1000 posted:

Sent you an email Bob, hopefully that will help you.

Got it, thanks.

Any other thoughts on how to proceed?  

Bob

Have you tried a Feature and Factory reset?

There is no reverse fet.  One motor fet, the relay changes polarity of the motor wires.  There is a diode for the relay to handle spike.  Maybe damaged. 

I am confused about operation.  Is this DCS?  Not sure why successfully switch to reverse but can't drive motor FET, if it can drive forward FET.  Stumper.  Would been to see what voltage and current doing when you do it.  G

@GGG posted:

There is no reverse fet.  One motor fet, the relay changes polarity of the motor wires.  There is a diode for the relay to handle spike.  Maybe damaged.

I am confused about operation.  Is this DCS?  Not sure why successfully switch to reverse but can't drive motor FET, if it can drive forward FET.  Stumper.  Would been to see what voltage and current doing when you do it.  G

Ok thanks George. Yes I am controlling with DCS. I will look at current and voltage. Does the relay that changes motor polarity also control directional lighting?  If no, what is the best way to test if relay is functioning?  
Bob

George

You got me on the right path.  I checked the voltage and current when the failure occurred and there was no jump in the current.  So I thought, do I have dirty track or wheels?  I moved it to another section of track with no improvement. So as I was shooting a video to post, it reversed without shutting down.  I tested it a few more times with some successes and some failures.  

I checked the wheels and rollers and while they did not appear very dirty, I cleaned them with IPA and got a lot of black crud off.  Problem fixed.  It's odd that it only failed in reverse, but I was only running it a couple inches at a time.

Anyway, thanks George and others who posted.  And also thanks to the MTH engineers that designed a board that can handle 36v!  Or maybe is was the dirty wheels that offered the protection.

Bob

MTH boards can handle higher volts than the Lionel ones do (IME).

I run my G scale set at 25 volts for example. It sees about 21+ at the rails.

I fried a Lionel board by accident with the handle set too high on my Z4000. They don't go above 18 volts.

Higher voltages (above 25 on the rails for example) to MTH boards does seem to cause them to act weird. I didn't see them fry though. My Bridgewerks Mag25 DC pack on my G scale goes well above standards that O scale run at. That helps them run better outside where track voltages can vary over huge distances and several engines are on the rails.

I don't wish to argue with Rich here again about this but I'm convinced that a higher voltage is needed when the power draw is heavy.

I run up to 5 G scale diesels on a train with smoke on. Amps are low when the voltage is set higher. Maybe there's another reason?

If I lower the track to 18 volts, my 10 amp protection fuses will pop. If I run at over 21 volts on the rails, no issues. Might be something about power delivery I'm missing? I thought it was basic electrical theory in play.

Getting a little off-topic but I agree with you Joe. 24V has been the informal standard in G scale for years, and at least 20V in O scale with the ZW and 773 Hudson as salient examples.  In general, locomotives will start smoother and run better with lower current draw by using motors with higher-voltage windings.  We all would have been better off if Lionel had designed the electronics to handle 24V, and spec'd 19V or 24V motors in our trains.

@Engineer-Joe posted:

If I lower the track to 18 volts, my 10 amp protection fuses will pop. If I run at over 21 volts on the rails, no issues. Might be something about power delivery I'm missing? I thought it was basic electrical theory in play.

There is some logic to that.  Since most of the cruise systems drive the motors with PWM, a higher voltage into the board will result in less average current into the boards.  Given that the voltage drop is determined by the current flowing in the circuit, the higher voltage to the boards will result in less voltage drop due to less current to the board.

You can vividly illustrate this effect measuring the voltage and current to the tracks with a single engine.  Run a PS/2 or PS/3 engine at 12V and observe the current to the track.  Increase the voltage to 24 volts and note the current drops to almost half of the current at 12V.

With that observation, it's clear that at 12V, the voltage drop in the wiring will be almost double the drop when running at 24V.  This also explains why the fuses blow, there will be less current at the higher voltages given the same speed and cruise control.