BLI Paragon 3 vs. 4 decoders

[Cajonpassfan]

I've purchased some BLI P4 equipped F3's and F7's to replace a couple of my B unit dummies; they do play well together with the P3's and the additional capacitance of the P4  is a good improvement. The only difference I can see in the two boards is the additional third cap on the P4, see pic, but the improvement is substantial.

Unfortunately, while "servicing" one of the older P3 equipped F3's, I must have tweaked a connection somewhere. The previously fine running unit is now sound only, with a dead motor. Poking at the board and pressing down on it, there's an intermittent connection made and the engine takes off. I think I've narrowed down the problem the white connector on the side of the board; when pressing down on it the loco comes to life, but just temporarily. Sorry about my ignorance, but I don't quite understand how to disconnect and reconnect that particular connector without damaging it. There appears to be no obvious way to disconnect it...do I pull it up, or sideways? Or?
Advice appreciated,
Otto K.

[peteski]

I also have a hard time to believe that just that extra cap would make so much difference.

The connectors on the BLI locos I currently have handy have little shoulders on the ends so they can be pried out more easily. But these look like they don't have those shoulders.  You would just have to pry them out. It is not the easiest thing to do.

Since you didn't disconnected to cause the problem, I'm not sure if the actual connector is the problem.  It might be a cold solder joint to one of the connector's pins, or elsewhere on the PC board, near the connector.

[Cajonpassfan]

Thanks for the response, Pete, appreciated.
I'll attach two more pics showing the offending plug (?) in better detail. It's the one marked blue. You can see it's hollow to the side; I'm not sure I understand what it's connecting to what... but when I press down on it, the loco moves, when I stop so does the loco.
I've poked at it with a large toothpick all around the board and it only responds there or in very close proximity.

Or, another possibility, are there any contacts underneath, on the back side of the board, that need to be firmly pressed in place? I'm afraid of unscrewing it and opening another can of worms unless I know that could be the problem. Anyone who has a P3, perhaps one removed from their loco? What and where are the connections between the board and the motor?
Thanks again,
Otto K.

[Mike C]

   That's not a connecter , it's a chip .  It could have a bad solder joint , is the loco under warranty ?   I'd probably say that there is there is a crack somewhere on the board as Peteski mentioned .    Mike

[bigdawgks]

That is absolutely a connector. All the paragon boards have at least 2 of them, but not all may be used in every model.

[Mike C]

   Hmm I sit corrected 

[Cajonpassfan]

Thanks. Can't be a chip, it's hollow, and it would make sense that perhaps this connector is not in use on this F3 (no extra lighting etc.).
And I remembered I have an extra P4 I acquired a while back and it has no contacts on the back side, just a bunch of chips, so the motor must be fed through a pair of the end connector pin outs. Which ones?
Saga continues. Suffice to say this is not what I enjoy the most about this hobby....
Otto

[peteski]

When Otto posted the additional photos, like Mike I  was also a bit confused because there were signs of blue on couple other small components besides the dab of blue on the unused connector.

BTW, that connector shell seems a bit distorted (melted)?

Otto, as you suspect that connector is unused and has no bearing on any motor connections.  I originally thought that you were talking about the connector  which actually has the motor leads.

Anyway, if pressing on the board fixes the problem than as I mentioned, there is  likely an issue with either cold/fractured solder joint somewhere, or cracked trace. Can't you trace the motor wires  to  see which connector they lead to?  You should really be able to safely remove the screws to slightly lift the decoder to see if you can trace  the wires.

The orange and yellow wire on one connector seem to be fed into a hole in the chassis. Are those far a headlight or maybe motor?  If not then there is only the connector on the other end of the decoder, so the motor leads must be on that connector.

I also see that it looks like you snipped off the Sound of Thunder ^TM wire antenna, and some wire strands stayed on the decoder.  Those aren't shorting to  anywhere on the PC board?

[Cajonpassfan]

Thank you Pete @peteski for your feedback and advice. Yes, the thin connector cover got distorted by me, pushing at it at fairly hard to get the loco to respond. No damage to anything else. I also clipped back the antenna leftovers even though they weren't touching anything. A problem waiting to happen.
I took your advice to track the wiring: The orange and yellow wires go to the speaker and the only two other wires going to the rear connector (grey and black) is rail power from the trucks. Motor and light connections are all at the front connector.

I *think* I got it figured out now. Pressing on the connector was a red herring, the problem apparently was an intermittent connection at the left of the rear truck. Once I started pressing down on the frame in lower left below the connector, I got the same response and I tracked the problem down to the "Kato-style" copper wiper/nub. I rebent it carefully and polished the mating surfaces with some 1200 emery paper, applied a bit of CRC, an voila, everything works (for now too early to celebrate pending testing the four unit set thoroughly on the layout, see pic).

As to why sound and lights were working properly while the motor was dead is a mystery to me. Is it possible enough current was getting through the front truck to run the sound and lights but not enough to supply power to the motor? Or do I have another unpleasant surprise coming?
Thanks for following,
Otto K.

[peteski]

As to why sound and lights were working properly while the motor was dead is a mystery to me. Is it possible enough current was getting through the front truck to run the sound and lights but not enough to supply power to the motor? Or do I have another unpleasant surprise coming?
Thanks for following,
Otto K.

Electrically that makes no sense to me Otto.  If the bad contact with the track through the trucks and any contact areas involved, that would affect all the electricity consumers in the model.  Bad contact mains "high resistance) hig resistance causes voltage drop to everything that is connected in the circuit.  The motor is the highest drain of electricity. Even if the contact resistance was not low enough not  to cause enough voltage drop to make the voltage at the decoder to still allow the sound part of the decder to work, as soon as the decoder powered up the motor, that wold cause increase of the current draw which would (due to poor contact at the truck) drop the decoder's voltage even further, causing both, the sound and motor to stop working.

But if it seems to be fixed then just use it and hope the problem will not reoccur.

[Cajonpassfan]

Yea I know. But she's been running up and down the Pass with a '51 Super Chief set all evening. Two P3 A's, one P4 B, one dummy B.
So far so good...
Otto