MTH BB-1 Rear Coupler Not Firing

BBasalikOGR Forum Member

Hello everyone,

I've got a slightly quirky issue with my PRR BB-1 (MTH 20-5561-1) couplers. The lead engine's coupler fires just fine, both in conventional and under DCS.
The rear (in this case slave unit I guess) coupler does not.

I checked the coupler, and it works mechanically and electrically (this was done by hooking it up to a different locomotive of on a parallel track and using the firing command from that locomotive on the BB-1's rear coupler.)
After checking the wiring from the harness to the black molex plug for the coupler, everything seems to be in order. No pinched wires or disconnects.

Is there something I'm missing, as I'm presently at a loss.

12/16/2210:00 PM

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Jon GOGR Forum Member SUPPORTING MEMBER

It’s either continuity through the harness (shells removed, checking from the board to the coupler) or the FET on the board is fried. Bringing it to an ASC that has a PS2 tester will verify it.

12/16/2210:30 PM

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Alan MancusOGR Forum Member DIGITAL SUBSCRIBER

Hi, you need the couplers MTH part number are DD0000032 and DD0000033 depending on which one you really need! I agree with Jon G.

you could have a bad FET!

I:\Instruction Manuals\Premier\Electric\20DL10060I_BB1&BB3\20DL10060I.PDF (mthtrains.com)

Alan

12/17/228:41 AM

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gunrunnerjohnOGR Forum Member SUPPORTING MEMBERDIGITAL SUBSCRIBER

If the FET is bad, there's usually a reason. Check the coupler carefully as well as all the wiring. If there's anyplace along the line that the wiring could connect to ground, that will quickly cook the coupler FET on the board.

12/17/229:40 AM

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BBasalikOGR Forum Member

Far as I can tell, there is no ground contact.

I actually had a spare coupler I could test that I knew was good.
Swapped couplers out, nothing. Old coupler worked just fine on my tester locomotive, so I suspect that FET may have gone bad somewhere.

The locomotive still runs like a champ, it just only has one working coupler.

12/17/2210:24 AM

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