Graham Farish N Gauge Class 25 DCC problem

[paulontheball]

Hi unusual one I could do with some advice on please.

 

I have an N Gauge Farish class 25. It's about 4 years old and has always been a good runner with a Lenz silver chip. The control system is Lenz 100.

 

Recently I was running the loco on the layout when it stopped for no apparent reason and then proceeded to back up for a very short distance before stopping altogether. It then remained dead.

 

I've since spent ages trying to fault find but still can't find the fault. Things I've tried:

 

1. Reset/reprogrammed the DCC chip - no change

2. Swapped the chip with another - no change

3. Retested the chips in a chip tester - all worked fine.

4. Removed bogies and checked gears - no split gears

5. Bypassed all electrics after disconnecting them and connected a DC supply direct to motor contacts - bingo!, the motor runs fine with no load

6. Checked solder joints and retouched any that looked poor on main Pcb

7. Checked lights - they work fine, switching on and off and reversing

8. Cleaned all contacts - no change

9. Checked contacts from Pcb to motor contacts and just bent them in a little more to ensure that they connect

 

So in summary, the chip is good, the motor runs fine (with no load), the lights are working, the contacts appear clean and are touching so it leads me to think that the Pcb on top of the loco has failed in some way but looking closely it just contains surface mount ceramic capacitors and resistors - I struggle to see what could have failed.

 

Any ideas would be appreciated!

 

Regards

 

Paul

Edited November 1, 2018 by paulontheball

[kev]

A lot of fault finding hold up to bright and see if there is a crack in it ,can you get rid of the pcb and hard wire it ,vero board i think it is called could be used to replace pcb,do not know if a new board is available ,i am sure others will be able to give you more info but from what you have put i would think pcb

[Paul80]

If the directional lights are still working then it's an issue with the motor circuit, using a meter on low resistance or diode test mode, test for low resistance between pins 1 and 2 on the decoder to the contacts to the motor. If either gives a high resistance then that would suggest a brake in the circuit, if you are good with a soldering iron you can run some thin wires from pins 1 & 2 direct to the motor pickups, as the motor feed does not go through any of the components on the PCB they are there for the lights.

[Steven B]

Does the loco behave on DC if you swap the decoder for the DCC blanking plug?