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Still a problem with a GP9

1802 Views 3 Replies 3 Participants Last post by  dawinter
Ok you electronic wizards….

Thanks again Paul but.....

I’m usually pretty good at logical trouble shooting but I’m stumped with this one and I have to move on. Perhaps someone can help…

1. New lamp PCB’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 GP9’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 PCB’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 ½ bright and stay that way as voltage increased.

Should I just order a new main board?

Thanks in advance.



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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
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.
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.

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