Re: 3V BCR capacitor polarity

Jeff_the_Coaster_GuyOGR Forum Member SUPPORTING MEMBERDIGITAL SUBSCRIBER

Hey guys,

I'm confusing myself at the moment while I install a PS2 BCR.

In @gunrunnerjohn s posts, he has a photo of a supercap and mentions to connect the positive lead to the positive wire from the PS2 harness, and includes this photo:

Looks simple enough... But from my harness I've got on my table, the red wire appears to be in the other side of the connector:

The connector is black instead of white, but as far as I can tell they're the same connector series and the retaining flaps (the tiny flaps that lick the crimped ends into the connector) are on the top in both of our pictures.

John, did you switch the red and black wires in your connector?

I suppose the question is really which pin the positive leg of the capacitor needs to connect to in this photo: positive to pin 1 or positive to pin 2?

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10/9/229:17 PM

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Vernon BarryOGR Forum Member SUPPORTING MEMBERDIGITAL SUBSCRIBER

Yes, and what should be said is buying factory pre-crimped connectors may not match the MTH polarity. Simply re-pin your connector or reuse the factory connector.

Again, consider the original connector as "the standard".

10/9/229:24 PM

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Jeff_the_Coaster_GuyOGR Forum Member SUPPORTING MEMBERDIGITAL SUBSCRIBER

@Vernon Barry, thanks for the feedback. I suppose I'm still a bit confused though, as I don't think it's likely that @gunrunnerjohn would wire his BCR wrong and post a photo. But unless the red wire in his photo is attached to the negative leg of his capacitor, it seems like it's different from the factory setup on the PS2 board? However, in his instructions, he clearly says to wire the positive leg of the capacitor to the red wire from the original connector.

I hope John chimes in soon. What's frustrating is that I made three of these 2 years ago and they're working great. But I forgot how I wired them and I'm not at dad's place to get into those engines and see what I did.

10/9/229:32 PM

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Vernon BarryOGR Forum Member SUPPORTING MEMBERDIGITAL SUBSCRIBER

For a 3V PS2 setup, either reuse the original factory harness and connector when soldering to the 5V rated super capacitor, Red to positive of the super cap, black to the negative (white stripe) side of the super cap.

If you buy premade connectors- they may not match the pinout polarity. No problem, just repin by extracting the wires and crimped ends by prying up the plastic tab of the connector and make it match the original harness.

10/9/229:36 PM

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Vernon BarryOGR Forum Member SUPPORTING MEMBERDIGITAL SUBSCRIBER

Confirmed on a genuine MTH PS2 3V harness as plugged in.

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10/9/2211:55 PM

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Vernon BarryOGR Forum Member SUPPORTING MEMBERDIGITAL SUBSCRIBER

The capacitor is just replacing the battery. Red is positive, black is negative, there is no trickery going on here. Especially on a PS2 3V.

Just like I often do, buying bulk pre-made JST-PH connectors there is no "standard" and so from brand to brand, batch to batch, you may find and buy different polarity. Again, bottom line, you are best to re-pin premade connectors so that your connectors match factory harness polarity. Nothing worse than trying to troubleshoot something with reverse color wiring.

What you may be confusing is the PS2 5V which uses the 9V style battery. This is important because you might also buy premade 9V battery snap connectors. The issue there is, the connectors are made to snap onto a 9V battery as a source. Thus, when plugged into a 9V battery, the red wire is the positive of the 9V battery. The flipside is, using that same bulk connector for making a capacitor replacement, now this connector is acting like the battery side. So unfortunately, the wires are reversed (red becomes negative of the super capacitor, black becomes positive.). Again, in this situation, because it is impractical to change the 9V premade battery snap wiring and swap it, instead we do take a shorcut and reverse at the supercap.

PS2 3V should be obvious- red to positive, black to negative of the supercap. If using premade connectors - correct and ensure the connector end pinout matched the MTH original wiring.

When plugged into the board

PS2 5V (AKA 9V battery style) when using the premade typical 9V battery snap- this is the exception where wiring reversed at the super cap. Again, this is because we know we are getting reversed premade connectors and cannot easily switch at the connector end. @gunrunnerjohn has also in that case, suggested using a non-prewired battery snap.

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10/10/2212:00 AM

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gunrunnerjohnOGR Forum Member SUPPORTING MEMBERDIGITAL SUBSCRIBER

@Jeff_the_Coaster_Guy posted:
Hey guys,
I'm confusing myself at the moment while I install a PS2 BCR.
In @gunrunnerjohn s posts, he has a photo of a supercap and mentions to connect the positive lead to the positive wire from the PS2 harness, and includes this photo:

That picture was a mistake before I noticed my pre-made connector cables were backwards from what was needed. That's the polarity of the cable used for Lionel RailSounds-Lite boards. Really, I don't make them that way.

To insure no misunderstanding, this is the correctly wired model! Sorry for the mixup, I only noticed the pre-wired cables were backwards after taking the photo and forgot to come back and fix it.