Hi, I have a PS3, GP9 diesel that has recently started to open the rear coupler randomly in use. This afternoon the rear coupler continuously ‘buzzes’ and won’t close at all.  I would appreciate any help with this please.

David Yarwood

Original Post

If this shorted to chassis, I am sure you also damaged the coupler FET and it is shorted proving continuous voltage/current.  The board needs to be tested and repaired most likely.  IF you put a new coupler in and wire is all good and it immediately buzzes with power applied, turn it off until board fixed.

Couplers also can occasionally short internally, so that may be the issue, but need to ensure board not damaged.  G

MTH Authorized Service Center

Authorized ERR Dealer

Lionel Independent Repair Tech

Virginia Train Collectors Member

GGG posted:

If this shorted to chassis, I am sure you also damaged the coupler FET and it is shorted proving continuous voltage/current.  The board needs to be tested and repaired most likely.  IF you put a new coupler in and wire is all good and it immediately buzzes with power applied, turn it off until board fixed.

Couplers also can occasionally short internally, so that may be the issue, but need to ensure board not damaged.  G

George,

Have you replaced a coupler FET on a PS3 board yet?  They are pretty tiny.

Dave

David Minarik posted:
gunrunnerjohn posted:

I can't even find Q76 on the board or the drawing.

They are Q221 and Q228   roughly middle if the board left to right.  Right below the middle cap.

Stupid me, I was looking at the steam tender board.  However, the list of replaceable parts says Q76, but the steam tender board doesn't have that part.

Those parts on the diesel board are the SOT-23 form factor.  Small, but not impossible to replace.  For stuff that small, I tend to use the small nozzle on my rework station and just release the part and flick it off.  Then I can heat the new part holding it on the pads, usually that works.

Yes I have.  I have occasionally jumped the led resistor stack also with a thru hole resistor if you lose a headlight and the buffer chip is good. 

Biggest problem is too much heat when fails that damages traces.  G

MTH Authorized Service Center

Authorized ERR Dealer

Lionel Independent Repair Tech

Virginia Train Collectors Member

You have fancier stuff then me.  I just use an iron.  The coupler chips are not hard to come off.  As far as the lighting buffer, I soldered a normal resistor across the pads.  Have to be careful because of close spacing.  I think the new chip is larger, but would need a hot air set up to remove in my opinion.  G

MTH Authorized Service Center

Authorized ERR Dealer

Lionel Independent Repair Tech

Virginia Train Collectors Member

Add Reply

Likes (0)
Post
The DCS Forum is sponsored by
OGR Publishing, Inc., 1310 Eastside Centre Ct, Suite 6, Mountain Home, AR 72653
330-757-3020

www.ogaugerr.com
×
×
×
×
×