What's inside those Power "Bricks?"

[peteski]

That Bachmann unit you reviewed sure uses a very esoteric design I have never seen before.  Needlessly overcomplicated with no added benefits that I see.

[$2 Bill]

That Bachmann unit you reviewed sure uses a very esoteric design I have never seen before.  Needlessly over complicated with no added benefits that I see.

When you see stuff with weird wiring & such is often to Patent a device OR to bypass Patent(s) from others.

What gets me is 2 Breakers in series. I can't see Part # or other marks for them to see same or different values but make little reason. Plus 2 Polly Fuses.

Output to Trains seem Current "Regulated" but not sure just what/how over or no current acts. Maybe the Resistor is too high Ω to test But believe the unit is "Dead" as noted before. So I'm still watching Flea markets etc for another unit.

Maybe this Unit & similar from Bachmann is "Safe" for Coreless Motors now common for N & other tiny trains but even then 2 breakers make no sense.

[mmagliaro]

I have two comments on that odd Bachmann circuit design.
First, I'd ask you to double check that PCB to see if there is anything connected BETWEEN the two thermal fuses.  There appears to be a trace on the board going under one of them in the middle (on the left side of the board) and then snaking off and around down to R2, among other places.  There could be a reason for having two.  I seriously doubt they just put two breakers in series.

Second, as to the design of having two power transistors, one for each polarity, have to you tried flipping the direction switch
while the throttle is up to see how the circuit reacts?  It's hard to tell just from looking at the schematic, but maybe using the two
transistors creates a circuit that will gradually ramp down and back up in the opposite direction without jarring the train.

[$2 Bill]

Bachmann 46605A & related are 1 sided PCB & Parts are often used as "Jumpers."
Fuse 2 jumps over the trace for D1 & D2 1N5401. D1 & D2 also "jumps" traces but on the other side.
Edit--> The trace that "Goes under" Fuse 1 is the same one as Fuse 2 Jumps. IE Just connect those Diodes to "bottom" end of Fuse 1.
Blue follows the trace for the Diodes, Red Fuses. (Breakers are Riveted & solder to the board so not taking them off.)
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There is Nothing between Fuse 1 & 2. Look at pic for Transistors. Just right is D1 but nothing else on "back" of PCB there.
Edit--> second view "Back" of PCB
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As said before the unit is "Dead" & now lost too. (then found again for 2nd pic) Doubt the unit will "soft switch" the direction but if/when I find a "new" one I'll test this.
Can't find the PDF in manual right now. Thought said stop before changing direction like most others.

[$2 Bill]

Second, as to the design of having two power transistors, one for each polarity, have to you tried flipping the direction switch
while the throttle is up to see how the circuit reacts?  It's hard to tell just from looking at the schematic, but maybe using the two
transistors creates a circuit that will gradually ramp down and back up in the opposite direction without jarring the train.

Can't find a Bachmann PDF say much or anything for train direction.
Example: https://www.bachmann.co.uk/dbdocument/1019/36-565%20-%20Bachmann%20Train%20Controller%202018.pdf

So went to garage to look in the box to get Printed copy of EZ Track System that came with the "dead" unit.
Only Says...

To change your locomotive's direction, turn the speed controller to the "OFF" position and slide the switch to the left or right as needed.

Page 7 in doc TRAIN-IS121.

I don't see any "timing" to auto fade the speed by switch direction without bothering the knob. The "big" C1 C2 just smooths DC Ripple coming from D1 & D2.
But I'll check the idea maybe with a "junk" engine not just the resistor.

[peteski]

I don't see anything in that Bachmann circuit which would facilitate a gradual slowdown before reversing direction. I still shake my head about the squirrely circuit! It reminds me of those Rube Goldberg contraptions.  And each direction is powered by a half-wave rectifier (single diode) with a 1000 µF cap to smooth out the serious ripple.

[$2 Bill]

Yea, is weird.

Only Guess for Fuse2 is a "Throw Away" part to automate board build. Some times is cheap to "waste" a part so board fits given space or even work @ all then load whatever in pick & place machines, add inventory, etc.

1 or Both Polly Fuses is likely to Pass UL CE & other Testing.

Same box have different Cat No's for Other Counties with correct "Wall Wart," Safety & other Certs. UK & EU uses Different Plugs for 240VAC & deal with TUV etc.