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Looking for some diagnostic, and potentially hardware part number help.  I have the second generation Great Northern 2-8-8-2 (20-3384-1) released in 2010.  I purchased this recently new.  The engine performs flawlessly, however, the headlight burned out quickly upon running.  I took the engine apart and noticed that the harness for the bulb had an exposed wire.  I thought this may have had an impact on the bulb burning out.  I since have replaced the grain of wheat bulb (got new one and harness from Midge at MTH) and installed (these are 6V GOW bulbs).  The light worked briefly and then burned out again.  I reopened the engine again and checked the voltage at the bulb and connector on mini board on the engine and it showed 23.xx VDC on my voltmeter.  I know that these constant voltage headlights are supposedly PWM, but I figured I should see 6v at the connector.

Does anyone know what the problem could be?  Do you think the voltage regulator board could have gone bad (maybe the short on the exposed wires)?  Do I need to replace this voltage regulator board?  If so does anyone know part numbers. 

Below are pics of the inside of the engine showing the small connector board (appears to be multi connector board the 10 pin harness plugs into as well as the headlight light connector), as well as the board attached to the underside of the boiler (is this board in fact the headlight regulator board)?

By the way, all other lights work fine, marker, cab, rear tender light....

Thanks for your help and direction.

Greg

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the ps 2 board has a problem and is putting out to much voltage which is causing the light to burn out! Ill bet your light glass turns black that is an indication of over voltage GGG can repair your board!

if your exposed wire contacted the frame at one point that's what probably damaged the electronics in the ps 2 board. that can be repaired! or if you want a cheaper way you can  check the voltage on the light with a vom meter and just install a higher voltage light in place of the bulb that is presently in there

Last edited by Alan Mancus

It's fairly common for a ground in the wiring to take out the FET that drives the headlight, then you're getting around 18-20 volts on the bulb.  You need a board repair, replacing the FET is a fairly simple process and should solve your problem.  Since that locomotive has the mux boards, the FET in question is on the board in the locomotive.  The entire board can also be replaced, they're not that expensive.

All, thanks for your input.  I was thinking it was the transistor.

John, so the mux board I show in the pic that is attached to the top of the boiler is the one with the bad FET, and not the PS2 board?  Thanks for the clarification.  BTW, do you know the part number for the board?  I will either call Midge for the part or get with GGG, he has done some great work for me in the past when I fried a FET on a PS2 board.

Thanks,

Greg

 

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