Issues with a class 156 2 car set Dalpol

spitaljunction · May 13, 2020, 01:53:04 PM

Hello everyone, I'm a new member so I hope you'll bear with me if I make mistakes. I would like to know peoples experiences with their locos exhibiting the kinds of fault I've been experiencing with the class 156 DMU I bought 18m ago. Initially ran OK then after fitting internal lights started to exhibit the SVdA fault which I understand is a short circuit. I disconnected the internal lights but the fault persisted, sometimes it would run OK but generally speaking on powering up the layout the controller would display the fault code SVdA coming and going. I've had it back to DCC Controls twice under warranty with diodes having been changed on both occasions but the fault persisted. When in fault condition pressing down on the driven loco would clear the fault.In the last week I identified that removing the roof of the driven carriage would clear the fault, I then realized that the 2 plastic pins central on the roof structure which seem to be there to hold the seating assembly in place were causing the problem. I snipped them off and the loco is more reliable but still not 100%. Has anyone experienced this fault with this loco and what can be going on where a downward pressure on the seating can cause this kind of problem.

ntpntpntp · May 13, 2020, 02:42:53 PM

"SVdA" - never heard of that, what DCC system are you using which displays that code?

[edit] Ah, googled it. MRC / Gaugemaster Prodigy system

Steven B · May 13, 2020, 02:46:24 PM

SVdA is a Gaugemaster Prodigy 2 for a short circuit.

Does the fault occur when you have just the powered half of the unit on the track?
What about if just the unpowered car?
Do you have a decoder in the unpowered car? If not, is the DCC blanking plug fitted?

When fitting the lights did you dislodge any of the insulation tape around the light-bar connector or the decoder socket?

Steven B.

spitaljunction · May 13, 2020, 04:30:09 PM

The fault is related to the power carriage only, I originally had a 6 pin decoder in the carriage but removed it as I understand its purpose is to change the lights from red to white if running in reverse which I can live without and I had a need for a decoder for a new loco. I did not put the blanking plug in but I will replace it.
The insulation under the decoder chip is in place.
What I'm trying to get some info about is why a relatively light pressure on the seating assembly would create short circuits.
In answer to the first response I use a Gaugemaster Prodigy Express2 controller.

ntpntpntp · May 13, 2020, 04:37:41 PM

Quote from: spitaljunction on May 13, 2020, 04:30:09 PM
What I'm trying to get some info about is why a relatively light pressure on the seating assembly would create short circuits.

Could be a wire with damaged insulation maybe? Could be the decoder is not properly isolated from the chassis? Difficult to diagnose remotely by discussion, but it should be easy enough to track down and fix if you say the fault can be replicated with a little pressure in a certain place.

spitaljunction · May 13, 2020, 06:34:15 PM

Thanks "only me" that sounds like what I've been experiencing. As I said since snipping off the small prongs on the roof the loco has performed a bit more reliably. I'm amazed that the people at DCC weren't able to diagnose this for me.

robert shrives · May 14, 2020, 08:20:39 AM

Diagnosis is always a minefield- ask any GP ...

I bet the first thing was to pop off the roof and try a run so thereby removing the problem... It is good to read that also forum has played a positive role. Also has helped me with a 153 - I will look to adding a bit of tape under a seat unit.

Everyday a school day!

Robert

Izzy · May 14, 2020, 08:39:00 AM

I would not put the blanking plug back into the trailer if you are using it on DCC. Either fit a decoder or leave it out altogether. Otherwise the pcb circuit board will be subjected to the 15v AC current which it might not be able to cope with.

Izzy

spitaljunction · May 14, 2020, 12:34:42 PM

Thanks all for your help its been a good experience for my first post and good to know that I'm not alone if I get further issues with my layout.
As well as the DMU I run a class 68 loco, a steam loco Ulstarifleman and a class 37 which unfortunately failed on me just before the lockdown. I used my local model shop in Carlisle C & M Models to return it for repair, still waiting to see it again. I chose these locos as trains I have seen passing down the Carlisle to Barrow line which runs past fields behind my home.