Classic UK Minitrix Models  -  Gaugemaster Chip
Convert to DCC



The upper circuit board needs to be removed, and this requires disconnecting the green wire which is soldered where the green wire is shown on this picture.

When you remove the circuit board, the two grain of wheat light bulbs are free to fall out.  The front from  one side, the rear from the other.  Keep them safe.

Two shots of the upper circuit board in the Class 47.   The top photo shows the underside, the lower photo shows the soldered tracks.
The underside has 4 components that will need to be removed, shown above and below the long slot.

Above the slot - a choke coil of very thin wire protected on this model in a yellow sleeve.  To the right, a capacitor small, yellow with a green top.
Below the slot -  2 Diodes.

All 4 components each have two ends which are soldered on the top side.  It may be necessary to ease each connection out a little at a time, alternating between the two - especially the green/yellow capacitor.

None of these components are needed.  The capacitor and coil are used to supress ineterference.  The diodes allow the lights to operate in the direction of travel.  Both of these functions will be carried out by the DCC chip.

Do not de-solder any of the 3 bonze coloured connectors which stick out on the lower side of the board.  These are for the motor +ve connection and for the two light bulbs.

Take the motor out, releasing the two bearing clips at each end and the spring motor clips near the motor body (both described on pages relating to the motor).

Carefully remove the cap which has a solder tag on it.  Beware the spring and the tiny motor brush.  They can remain in place if the motor can be kept upright, but don't knock it over - those springs bounce a long way !

Solder a length of thin black wire to the tag - as shown.

Cover the tag with an insulating sleeve.  Here I have used some heat shrink tubing.  The idea is to keep this tag from touching the chassis.  A bit of card or tape stuck between the tag and the chassis would do just as well - until it falls out.

Replace the motor in the chassis - you will have to feed the wire through first.  Make sure the wire sits as shown, and then replace the axle bearing clips (see text and photos in the section on refitting the motor). The wire makes this a little awkward, and I found it easier to slot the motor into position loosely, ease out one end of the axle and put one axle bearing clip in place (loosely), and then do the same at the other end.  Finally push the motor home, and ensure the axle bearing clips lock into position.   Make sure the spring clips are properly inserted to hold the motor. 

Another shot of the motor, the motor earth wire and the green +ve track feed which comes from the lower circuit board.  The existing wire is good enough, but you may want to replace it.  Heed the precautions about removing the lower battery box before attempting this.
We can now use the circuit board for attaching the DCC chip.  The position of the White, Red, Yellow, Orange, Black and Grey leads are all shown on the diagram as small coloured rectangles.  The long thin green and black wires will be fitted later, but these represent the solder position of the green +12v wire from the lower circuit board and the black -ve feed from the motor.

Orange is connected to the Motor +ve brush cap by means of the bronze tag in the middle of one side of the underside of the board.
Grey is connected to the Motor -ve brush cap by means of the black wire that you soldered on earlier.

Red is connected to the +12v power pickup (which should be on the right) of the loco when it is facing forward)
Black is connected to the -ve power pickup (which should be on the left)  The chassis is used for the negative pickup, which comes through the axles.  It arrives at the board by means of the tiny rear securing screw.

White is for the forward running light and is soldered to the strip connecting to the front bronze tag
Yellow is for the rear running light and is soldered to the strip connected tot he rear bronze tag.

Here is a very messy first attempt to make sure that everything works.  I didn't make any attempt to tailor the wires to fit neatly at first - in any case, these would all lie flat under the roof of the Class 47 without any problem.  This being the first DCC chipped 47 loco that I had worked on, I wanted to make sure that all worked correctly.  The chip is a Lenz Silver Mini + and needs insulating on its underside otherwise the solder tracks on the circuit board will make contact.  A thin piece of tape over the top helps keep things in place.  The blue wire is not used - it is intended for the common return from the two lights, but as wired, the lights are 'earthed' to the chassis - which is connected to the -ve rail.  This is perfectly Ok, although the bulbs are slightly dimmer than if the blue wire could be used.  Its not noticeable.   All that remains in this picture is to fit the circuit board, and solder the green and black wires.  See the little notch at the lower left hand end of the slot ?  Thats where the green and black wires need to be routed.

Look at the lower bobs of solder under the blue wire.  You don't want your soldering to look like that.  It has a 'graininess to it, and in this case is caused by me when I removed the components - heating the solder and then blowing from the reverse side to clear the solder from the hole !

Here's another shot with everything in place apart from the loco body.  The blue wire needs to be insulated at the end as yet.  I have left the black and green wires too long to allow the top to be moved out of the way without desoldering - should I ever need to get to the motor.

Here is a sequence of 5 photos taken from the second Class 47 that I fitted with DCC.  The Lenz chip is quite expensive, but it is thin and tiny and fits easily inside the roof space.  For this experiment, I wanted to compar the Lenz with a cheaper model - in this case the Gaugemaster 2 function 36-558A.  It comes with 6 pins, so it needs a harness to connect it.  The chip and 6 pin socket/harness are much thicker than the Lenz, and the loco body will not fit on if the chip is put in this position.  I ended up cutting a rectangle out of the circuit board so that the chip would sit a couple of mm lower, and this just about gave me the required space.  But the body is still a tight fit.

The wires are cut more or less to length.  For this incarnation, I have used a red wire from the +12v feed from the lower circuit board, and looped it around to give the freedom to remove the upper circuit board without de-soldering.  Confusing that there are two black leads.  One can be seen emerging near the chip harness and disappears to be soldered on the square silver patch under the U bend in the red wire - to make contact with the chassis via the securing screw.  The -ve motor feed is the black wire that is soldered to the silver rectangle patch at the right hand end of the photo - to connect with the grey wire.

In cutting the ractangular hole in the circuit board, I had to destroy the connection for the lead from the right hand rail +12v (shown as the green lead in the above photos).  Instead, I have soldered this on the other side of the board. 

Same thing from the side.

And again showing the motor and black wire.

Ready to go.  Well, once it has its wheels and body put into place.  The bogies will physically fit at either end, but to retain the polarity of the chip and for the loco direction to be consistent with other locos on your layout you need to check that the insulated wheels - ie the wheels with the pickups - are on the right hand side of the loco.  Difficult to see because on mine, the pickup strips are painted black.  This puts the traction tyres on the rear bogey, but if you or a previous owner have had the bogies apart, this may not be true.

Maintaining Classic UK Minitrix Locos
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