Farish 108 problems

[TomJ]

Since going DCC my Farish N gauge 108 DMU has given me nothing but trouble! It burnt  a chip out at the start (no idea why, perhaps I installed it wrong?). Then it worked for a while but then gave up the ghost completely. Sent it back to Bachmann service department who simply fixed a few pickups that weren't connecting properly.

Seemed to run ok since then but no where near as smooth or as well as other stock. Looking at it today I realised that the real bogie (the power one) wasn't picking up at all. Carefully took it apart - seemed the copper pick up strip wasn't touching. So very gently adjusted it - seemed to be all connected. But on trying to run it things went wrong again! In one direction it runs fine but in the other just whines and smokes from the decoder!! Taken out the decoder and on DC test it runs fine (except the rear bogie is still making poor contact!) but nothing on trying the chip again. When I try to reprogram it says 'short circuit detected'. I haven't touch anything else or any of the wiring so don't know where this has come from.

 

So where do I go next?? Do I try another chip. Worried I'll burn another one out. Send it back to Bachmann? If they test it on DC it will seem to run fine. Or stop throwing good money after bad - buy a new unit and condemn this one to live as an unpowered dummy??

 

Any advice gratefully received. Its not doing my blood pressure any good!

[Nigelcliffe]

Though not in every example,  I have known Farish 108's to suffer shorts where the motor is connected to the PCB.  The pins/prongs which descend from the PCB can (if poorly adjusted in assembly) touch the chassis block.   Rough handling, and applying too much twist pressure when removing the body can make this short appear and disappear when assembling/disassembling.

This short has no bad effects on DC running, nor will it show on simple DC testing. The short simply connects the pickup (which comes through the split frame chassis) to the motor, which is what the blanking plug achieves anyway. 

But, such a short can be curtains to a DCC decoder as it delivers track power to the outputs of the decoder's motor circuit. 

 

So, look very carefully where the motor connects to the PCB, and consider adding a small amount of tape to the chassis block in the area to ensure that a short cannot occur.  It is possible to check for this short with a multi-meter and the blanking plug removed; it should show no path from brushes to pickups/wheels. 

 

 

Most of the other issues sound like poor assembly/adjustment of pickups.  There is a careful knack to get things correct in any N loco; too much pressure can be as bad as too little.  

Not running in reverse needs checking on DC first; if it happens on DC, then start looking for split gears (famous Farish feature !).  If smoke has emerged from a DCC decoder, then a fair chance that the decoder is now damaged in one direction (so scrap), but I'd still be checking the motor to PCB prongs above.

 

Though a bit harsh, if a decoder doesn't program correctly on a programming track, and the programming track reports a fault, and you then run it on the layout there's a certain amount of "well you asked for it to smoke".   It should not be possible to "smoke" a 6-pin DCC decoder by plugging it in the wrong way round.  All that happens is that the decoder outputs to the motor are connected to the lights, so it won't run. 

[TomJ]

Thanks for the tips - much appreciated. To be honest I think a lot of the problems stem from all the problems I had getting the body off in the first place. Some glue and leaked from the windows to the chassis making removal very difficult - I wonder if I damaged/moved pick ups in the process. I'll check all the pick ups and connections.

 

In my defence it started smoking before I re-programmed it!!! It was running ok ish (but only picking up from one bogie) so I adjusted the pick up and put it back on the track. Then it started smokng!! I quite removed it and put it on the programming track but damage done. Luckily only a cheap Bachmann decoder.

[PaulCheffus]

Thanks for the tips - much appreciated. To be honest I think a lot of the problems stem from all the problems I had getting the body off in the first place. Some glue and leaked from the windows to the chassis making removal very difficult - I wonder if I damaged/moved pick ups in the process. I'll check all the pick ups and connections.

In my defence it started smoking before I re-programmed it!!! It was running ok ish (but only picking up from one bogie) so I adjusted the pick up and put it back on the track. Then it started smokng!! I quite removed it and put it on the programming track but damage done. Luckily only a cheap Bachmann decoder.

Hi

 

Any time I make an adjustment I always put it on the programming track first just in case.

 

Cheers

 

Paul