Help required with Mehano G 1206 Vossloh Diesel Lighting PCB

[sncfbill]

I have a Mehano Vossloh G 1206 which has taken a tumble from my layout. After reassembly the LED reversing lights do not work and a resistor has burnt out on the PCB.   The resistor fitted by Mehano is dark brown in colour with a 1 black and 1 green band and I am unable to find one of the colour to replace. Can I use a substitute and if so what value ???  Attached photo

of top of lighting PCB

[jpendle]

Hi,

 

Resistors have 3 or 4 colour code bands so I suspect that what burnt out is a diode. On the small mezzanine board there is a Surface Mount LL4148 diode. Assuming the two solder pads below it are where the burnt out component was, then I suspect you need to add a replacement diode there. Your photo is a bit blurry but I think you would want to mount it with opposite polarity to the diode that's already there.

 

Regards,

 

John P

[Huw Griffiths]

Just out of curiosity, did this board work properly before the fall?

 

In case anyone's puzzled by my question, if the board worked correctly before (and the diodes weren't replaced), this would make me question the "diode polarity" theory.

 

 

Edited May 10, 2022 by Huw Griffiths

[sncfbill]

Thanks Huw yes the board worked OK before the fall - after putting everything back - some

of the delicate wiring to the light board had become unsoldered and I reconnected as I

thought from the numbering on the PCB  When track tested the loco smoked and the

component now missing had burnt out.

[sncfbill]

Many thanks J.Pendle for your valuable info on the diode reference I gave up searching and passed the loco to a local repairer - I have given them the reference in the hope it will aid repair. 

[Stephen Freeman]

I believe it is what is known as a Schottky Diode, which are faster switching than your normal diode, presumably they think the LEDs need more protection than usual.

[jpendle]

Hi,

 

They're just general purpose diodes in a SOD-80 surface mount package. They are used to switch between head and tail lights depending on which direction the loco is running.

Dapol use them in the same way on some of their loco PCB's.

 

Regards,

 

John P