dcc

[eddyld]

I bought a Bachmann gp9 L&N ROAD # 506 AT AUCTION. DCC on board. question is do these locomotives come programmed with the unit number already on the chip?

[Hunt]

From the factory, the decoder address is 3 for all Bachmann decoder equipped locomotives.

If your locomotive is used,  the previous owned may have set the decoder address to the locomotive road number.

Program 8 to CV 8 to reset all CVs to their factory default value.

[jward]

your best bet is to contact the seller and ask him what address he programmed into the decoder.