Model Railway Forum

Hi guys hope you can help me
I had a surface mounted point with a guagemaster rely in line to operate led to show what they were doing worked via a CDU and normal switch.I change this to a accessory decoder instead of the switch but now the relay dosen't work.

Any Ideas why as nothing much has changed it still has a CDU?
thanks

At the best idea either the accessory decoders CDU isn't as powerful as what you removed and its not latching the relay. or that the pulse that the decoder is sending is too short compared to a push button operation.
What accessory decoder are you using? as some have inbuild relays so would allow you to do away with the GM unit

Hi
Really could do with a bit more information... Relay unit.. Is this the Gaugemaster GM500 or the GM500D or something else??

You're Accessory decoder outputs DC and the 'C' connection is common Positive to the '+' and '-' connections which are switched negatives. This is possibly the reverse of how you originally had it wired using a CDU, where it is more conventional to switch the positive to the motors and have common negative return

Assuming the relays are the GM500, they will not work with an Accessory decoder as they have on-board diodes that are blocking the relays operation. You need the GM500D version for use with a decoder.

thanks for your reply. I have a PC2 train tech decodder and Its the guagemaster 500 relays that I have guess ill have to change it for the digital ones, try to make wiring simple hasn't realy help me