# Still a problem with a GP9



## dawinter (Jan 2, 2008)

Ok you electronic wizardsâ€¦.


Thanks again Paul but.....


Iâ€™m usually pretty good at logical trouble shooting but Iâ€™m stumped with this one and I have to move on. Perhaps someone can helpâ€¦


1. New lamp PCBâ€™s installed in a GP9. (The old ones were removed for another engine and new ones ordered from USAT.)


2. Engine tested on track with other GP9â€™s and seems to run well â€" in the correct direction etc. Starts to move (on rollers) at 1 volt.


3*. Cab light ok.*


4. Both lamps PCBâ€™s have *NO headlights - in either direction*. (four lamps test ok â€" not open cct anyway)


5. *Marker lights* come on, and flicker, at 6 â€" 8 volts rather than usual 3 â€" 4 volts and are always indicating the wrong direction. i.e. *always red on the going forward end and always green on the going backward end. *


6. Number board lights seem less than about Â½ bright and stay that way as voltage increased.


Should I just order a new main board?


Thanks in advance.


Dave


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## tjburger (Jan 2, 2008)

A quick brain phart, is the connector from the lamp wiring turned around and plugged in 180* out????? 
Just a thought, not looking at the moment. Could the board be turned around??? 
Hopfully someone with actuall knowledge will help


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## Skip (Jan 2, 2008)

Look for polarity reversal to the headlight boards - are they LEDs ? if so, they are polarity sensitive. The boards may not be seeing the right polarity from wherever they are sourced.


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## dawinter (Jan 2, 2008)

Thanks guys 

Turns out the two NEW lamp boards I got from USAT were wired in reverse and I did not have the old ones to do a quick comparison. Anyway, I turned the blk/wht and the grn/yel pairs around and I have proper operation of the markers at both ends. 

Still an issue though. No headlights on either board. Hard to believe that four bulbs are blown out. I'm building a 6VDC PS (batterys) to check out the boards away from the engine. Also ordered a main board. The regulator is probably trashed on one board due it being attached to the same heat sync by former owner. 

I set this project on the shelf for a day or two so I can do some of my own building. 

Dave


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