Failed NCE PowerCab

[Teditor]

My NCE Powercab has stopped functioning, cleaned contacts then I tried a new membrane and noticed a faulty pin on the IC (like as if the metal tab disintegrated), put in a new 165B IC and still no luck, tried another cord, no different.
Display is fine, here is what the buttons are doing;

Direction - OK,

Momentum - OK,

INC Fast - OK,

DEC Fast - FAIL,

INC - FAIL,

DEC - OK,

Potentiometer - OK,

Horn - FAIL,

Bell - OK,

Headlight - FAIL,

Optional - OK,

Select Loco - FAIL,

Macro - OK,

Recall - OK,

1 -OK,

2 - OK,

3 - OK,

4 - OK,

5 - OK,

6 - FAIL,

7 - OK,

8 - OK,

9 - OK,

0 - FAIL,

Enter - OK,

 Setup - OK,

Clear ? (because I can't select locos),

Add ?,

Del ?,

Prog - OK,

EXPN ?,

28/128 - OK,

Shift ?

Yours in Model Railroading Ted (Teditor) Freeman

[Cajonpassfan]

Ted, I've had my NCE system since 1999, and own four hammerhead cabs upgraded to radio. Over the years, I've sent three of them back to NCE for service due to minor issues. In each case NCE repaired the cab fee of charge other the  cost of shipping to them. Always excellent service although there's no acknowledgement of receipt or of shipping, but they are trustworthy folks. A repaired cab just shows up within a reasonable time.
I would start there at this point, but call them first as there have been availability issues with some of their chips. Good luck!
Otto K.

[peteski]

Ted, as I mentioned in the LokSound forum, you might try tracing the connections to see what connections the failed buttons have in common. Then you can try to pinpoint the problem even further.

[Teditor]

Peteski,
Beyond my capabilities I'm afraid.
Ted (Teditor) Freeman

[woodone]

Sounds like a good time to send it back to NCE.

[peteski]

Ted lives "down-under" so round trip shipping charges might add up to a non-trivial amount.   

[Teditor]

That is a problem, postage cost may outway the cost of a new one.

[peteski]

I could try to trace the non-functioning buttons for you to see if they have something in common, but I have very little workbench time available lately.

[Teditor]

Just gave a very careful clean of all the contacts "again", now none of the number buttons work, going to take it to the club and see if it will act as a controller on our Power Pro system, if not it may just grow wings.
Ted (Teditor) Freeman.

[peteski]

If the cleaning made things worse it is a good sign (that it is the switches themselves,  not electronics).  What are you cleaning those gold contacts with?  You might be just smearing whatever is coating them.

I hope you also cleaned the black conductive contact "pucks" on the flexible membrane.  Those sometimes leach out some sort of fluid which can prevent them from conducting properly.  I use isopropyl alcohol to clean those "pucks".  I woudl even go as far as cleaning them multiple times.

I occasionally have to take apart and clean my remote controls for TV, etc. and it does wonders for restoring their functionality.

[Teditor]

Did them originally with isopropyl alcohol , just did them with contact cleaner, quite a lot of black from the pucks.

[peteski]

Did them originally with isopropyl alcohol , just did them with contact cleaner, quite a lot of black from the pucks.

Actually the black stuff needs to stay on them. It is a carbon-based conductive paint that completes the electrical path between the metal contacts on the circuit board.
Some contact cleaners also contain contact lubricants which work well for metal-to-metal contacts, but might actually degrade the contact of the "pucks".

Since you mention that the problem got worse, maybe give them another alcohol cleaning.

Also, the keyboard is shared between the ProCab and Power cab, so I doubt it will behave any differently as a ProCab throttle.

[peteski]

Ted, over the weekend I mapped the keyboard connections  and as I suspected, I can pinpoint where the problem  is.  I'll try to post  the specifics later.

[peteski]

Here is a diagram of the mapped keyboard wiring.



The problem as you originally described indicates that all the keys you found failing are located in the column "A".  With that info you can isolate the problem to just few possibilities. If you have a continuity tester/ohmmeter, or have friend who is  handy with electronics, you can ask him to see if he can find where the problem is.  The trace from the microcontroller pin 24 to diode marked "1" can be eliminated because that signal is shared with the display board (serving another function).



This photo shows a short trace from the cathode of the diode "1" to couple of vias passing the signal to the other side of the board, and shows to which contact pads those traces lead.

Possible caused can be cold solder joints on the diode "1" (could refresh those joints to make sure they are good).  Then check continuity between the diode's cathode (on the side marked "1") to the top metal pad of the DEC FAST  button.  those are the only possible areas for an electrical open circuit.  It is also possible that the diode itself is defective.  These look like typical small-signal silicon diodes (like 1N914).

One thing that doesn't add up is the failing HORN button.  I'm wondering if there is another problem, unrelated to the other failed keys.
I also keep forgetting to ask: which pin on the original microcontroller chip was faulty? Was it by chance pin 24?

[eja]

Here is a diagram of the mapped keyboard wiring.


The problem as you originally described indicates that all the keys you found failing are located in the column "A".  With that info you can isolate the problem to just few possibilities. If you have a continuity tester/ohmmeter, or have friend who is  handy with electronics, you can ask him to see if he can find where the problem is.  The trace from the microcontroller pin 24 to diode marked "1" can be eliminated because that signal is shared with the display board (serving another function).

This photo shows a short trace from the cathode of the diode "1" to couple of vias passing the signal to the other side of the board, and shows to which contact pads those traces lead.

Peteski

Not sure what impresses me most - your knowledge or your willingness to help other model railroads.

Thank you for both.

eja