Re: Unidentified electronic Ckt breaker

Michael Sherbak

Thanks Mark
Appreciate you looking it over and the guidance


On Friday, September 19, 2014, Mark Gurries gurriesm@... [WiringForDCC] <WiringForDCC@...> wrote:
> On Sep 19, 2014, at 3:29 AM, Michael Sherbak msherbak11@... [WiringForDCC] <WiringForDCC@...> wrote:

> This was included in a used DCC system I purchased
> Was hoping some one could identify the brand/model so I know how to wire it correctly and may put it in service.

It appears to be a very early DCC circuit breaker design from a company that appears to be out of business.  In my quick search, I cannot find any internet information on the company “MicroDesign”.

What is unique about it is the use of PCB trace as a power resistor, the squiggly lines on the back side, to detect short circuit current flow to cut cost as opposed to using more accurate real power resistors.

I believe the RED device is a LED that lights up when the breaker has tripped.  An external LED is optional.   HOWEVER It looks like an external LED was used before for there appears to be a cut trace between the two wire holes for the external LED labeled “A” and “K” .   In order for the PCB LED to work, you must now re-short the “A” and “K” terminals together -or- install another LED to the two wire terminals.  The polarity of the LED is important.  Get it backwards and none of the LEDs will work or work properly.   Get jt right and both LED will glow brightly when on.

There two large holes which I believe is used to mount the PCB to some surface (wood) using some form of 1/4” tall standoff and an appropriate screw.

Given there is no documentation and I cannot look more carefully at the actual PCB board, I can only speculate on the connections based on the circuit I see.  Specifically I cannot make out the hole names for the two holes used for the red and black wires.  I WILL ASSUME the two wires hole labels are J3 and J3A.

There appear to be 2 sets of wire holes for input and output connections.  Large wire holes J1, J2 and J3.   Small wire holes J1A, J2A and J3A.

This implies there are electrically only 3 connections made to the PCB.   The black wire is going to be a common connection between the input and the output made externally from the board.  So you will need to “Y" the black wire into two wires to get the 2 in (booster) and 2 out (track) wire pairs.


The Booster Red wire input to J3A.
The Booster Black wire input to J3.
The Track Red wire output to J1.

But there is something wrong with the above connections from what I can tell.   There appears to be a small trace on the bottom shorting the J3A and the J3 as expected BUT as connected it is shorting the two Red and Black wires coming from the booster to each other shoring out the booster.   It sort of appears the small PCB trace started to burn near the black wire…. VERY BAD.      I think the J3A red wire coming from the booster is connected incorrectly.


Move the red wiring going to J3A to J2.  This should remove the short.  Make sure the red wire does not short to anything around the hole J2.

That makes the Booster/Track connections as follows:

The Booster Red wire input to J2 .
The Booster Black wire input to J3. (as currently done)
The Track Red wire output to J1.  (as currently done.)


Given this is a early DCC circuit breaker design, it is not suitable for todays DCC locomotives with sound.   It will shutdown prematurely.   I would retire this board and purchase a new modern “High Current Inrush” capable DCC circuit breakers.   There are two such products on the Market.   The DCC Specialties PSX-1 and the NCE EB-1.

Best Regards,

Mark Gurries
Electrical Engineer
DCC Website & NMRA DCC Clinics:



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