PS3 upgrade ABA protocoupler/resistor question

Read this 6 times.  Either DONOT fire the Fwd coupler or Keep the B or Trail A attached.  Alternatively you could wire in a coupler switch.  When in position Lead A Only you would have a resistor inside the engine engaged on the rear coupler signal wires.  On the Trail position it would go to the rear connector so that the resistor is out of the circuit and the Trail unit coupler is in.

Once may not damaged the board, but if done multiple times you may damage the board and or the fwd coupler does not work.  G

What's the harm of simply adding the resistor all the time?

Bryant,

I have a PS3  Santa Fe DL109 / DL110  AB engine that has a switch in the A unit to change from the Lead A rear coupler to the rear coupler on the B. That way you can use the A by itself and still have the Proto coupler work on the A unit by just using the switch. 

P.S,     20-20226-1

Now you got me wondering if I forget to switch the coupler switch when running just the A unit and try to operate the rear coupler, would it do damage? I'm petty sure there wasn't anything about this in the manual.

How about feeding the coupler with a jack & socket that closes a resistor circuit when the jack is removed?

It's really hard for me to understand why the resistor is needed, and if so, why it can't simply be left in all the time.

gunrunnerjohn posted:

It's really hard for me to understand why the resistor is needed, and if so, why it can't simply be left in all the time.

You probably could since it is such a high resistance and the low resistance coupler would not be effected.  The why you should know from the service bulletins.  Seems that if the circuit doesn't have a rear coupler in place and the forward coupler is used it may result in component damage on the board.  So some sort of design flaw you electronic engineers are so famous for  G

Leave the resistor in place, problem solved.  No switches, no special connectors, this seems like the obvious solution.

And that would be "some of you electrical engineers" buddy!

gunrunnerjohn posted:

Leave the resistor in place, problem solved.  No switches, no special connectors, this seems like the obvious solution.

And that would be "some of you electrical engineers" buddy!

Could I place this resistor inline on both couplers?  If so, which lead on the harness, not common I assume.

No, Not a series resistor, that would prevent coupler firing.  It is a parallel resistor, and only needed on the rear coupler for your application.  You have a forward coupler. G

So what do you do if an upgrade will not have a front or rear coupler? Do you still need the resistor to prevent damage to the board?

@H1000 posted:

So what do you do if an upgrade will not have a front or rear coupler? Do you still need the resistor to prevent damage to the board?

Yes, or else you will risk blowing the tiny FET.

@Vernon Barry posted:

Yes, or else you will risk blowing the tiny FET.

That's what I figured, thanks for confirming.

I don't know that is true.  If no couplers your not firing them, nor is there a low resistance load on the FET.  It is open.

This is not an instant damage thing.  Fire once and the fet goes bad.  It is a possibility to happen.  G

So maybe the worst-case scenario is that if you fire the non-existent couplers you'll blow the FET you don't need anyway or nothing happens except you get to hear the coupler release sounds.

I had an older 5-volt PS2 steamer that had a broken solder on the proto-coupler.  I fired the couple numerous times before I fixed it years later and it still worked after the resolder job.

This is interesting. I always figured people run their ABA sets as either 'A' alone, 'AB' or 'ABA' depending on what they're feeling like that day

I have a couple PS2 ABA sets that I have run just the lead A unit many times. If I understand this thread correctly, if I accidentally try to fire the rear coupler when doing this, I damage the PS2 board permanently?

Is this in the MTH manual? Seems pretty wild that this could happen so easily. Or is it more of a 'could happen once in a thousand times' kind of thing?

@Jeff_the_Coaster_Guy posted:

This is interesting. I always figured people run their ABA sets as either 'A' alone, 'AB' or 'ABA' depending on what they're feeling like that day

I have a couple PS2 ABA sets that I have run just the lead A unit many times. If I understand this thread correctly, if I accidentally try to fire the rear coupler when doing this, I damage the PS2 board permanently?

Is this in the MTH manual? Seems pretty wild that this could happen so easily. Or is it more of a 'could happen once in a thousand times' kind of thing?

Applies to PS3 Diesel/Electric board version

The reason is, a dual channel- 2 transistors in one "chip" package so firing one- somehow there might be kickback or ringing from local components or traces that kills the other FET likely from voltage spike. Good read up on why and how this can happen in a modern PCB https://www.pololu.com/docs/0J16/all

PS2 different board, different output transistors, thus not the same problem.

Applies to PS-32 also since bottom board is PS-3 diesel based. G