Classic UK Minitrix Models - Black 9F
Having 6 axles for the loco and 3 axles for the tender provides plenty
of pickup points for electricity, which usually means that this loco is one of
the most steady over points, round curves and over dirty track.
In fact, there are 5 positive (right) side pickups and 6 negative (left) side
Front bogie: Negative pickup
Front 3 drive wheels - Each has a positive and a negative pickup on the right and
left sides respectively.
Tender. The front and rear axles provide positive and negative pickup on the
right and left sides respectively.
||A clear view
of the pickups on the left hand side of the loco. Note that
the contact on the fron wheel is not made. At some point the
copper strip has been bent upwards, and only the centre wheel is
connected to the negative (left) rail. The rear two axles do
not provide electrical contact, they have traction tyres fitted,
although there may be occasional contact with the flanges, through
the axles and the chassis.
|Here is an
overhead view of the two copper conductivity strips. Note the
contact points for each wheel, and the extra contact at the front of
the loco for the positive end of the light bulb. This picture
also shows the red lead from the choke coil connected to the top
brush of the motor. If the motor is replaced upside down, this
wire will be at the bottom, and the engine will run backwards when
it should be moving forwards !
The cheese-head screw next to the
red wax which coats the choke coil, provides the main connection
between the left hand copper strip (negative) and the chassis.
On some locos, (like this one), this is the only secure connection
to the chassis.
||Here is the
copper strip being lifted out. The black wire is the positive
connection for the right wheel pickups in the tender. The loco
should run quite happily without this, although it may stutter over
points without the extra pickups provided in the tender.
||Here is a
different 9F from the right hand side with the circuit board in
place. Black wire goes to the tender. The green wire is
different, and is explained further down the page. Desoldering
the strips is easy, as soon as the solder melts, the strip spring
away (or up) from the circuit board. Re-soldering is a bit
more awkward. You need one hand for the soldering iron, one
for the solder, and another to hold the screwdriver which holds the
vertical copper strip in its place until the solder cools.
Don't let go before the solder has set properly, or you will get a
dry joint, which will not conduct electricity properly.
without its weight. The rear of the tender is to the left of
the photo. Note the contacts on the wheels at each of the four
'corners'. The tab at the rear has a hole in it, but has never
been soldered. This tab should stick up slightly. It
makes contact with the tender weight, when the weight is clipped
into place. (Note the 4 plastic clips sticking up from the
chassis.) The weight provides electrical continuity, as
described in the section below. The right copper strip (bottom
of photo) has a soldered tab sticking straight up. This should
have the black wire attached to it, which protrudes through the hole
in the metal weight. A plastic sleeve prevents any chance of
this tab and wire making contact with the negative weight. Note
the wire emerges from the tender below the coal shute at
the front of the tender.
tender which is attached to the loco. The loco is on the left
in this picture, so the negative (left) side of the loco is at the
top of the photo. You can see the clear plastic insulation on
the right hand wheels at the bottom of the picture. There is a
wire spring which provides the electrical continuity between the
loco body and the tender weight. The spring contacts the
joining screw, although in the models that I have, the screw has a
shoulder and doesn't tighten onto the eye of the spring. You
should make sure that the electrical contact is sound though, parts
have been known to have been painted where electrical contact is
necessary. Even when brand new. The open end of the wire
is sprung against the screw thread which protrudes from the bottom
of the tender weight. Grahame got in touch about a problem he
was having. His 9F would work fine when going backwards, but
was very erratic going forwards. The problem was traced to a
poor electrical contact between the eye of the spring, and the
middle joining screw which has accumulated a load of muck over the
years. He managed to establish that electrical contact to the
tender was broken when the tender and loco were pulled apart
slightly, but contact was restored when pushed together again.
Cleaning middle join solved the problem.
The connecting bar between the loco and the tender is articulated,
having 3 pivot points. The pivot point at the loco end can be
seen on the photo opposite (left hand end), and is unlikely to cause
a problem, but if the loco has been stood for a number of years, you
may want to check it out. A similar arrangement provides the
continuity at the right hand end for the front bogie.
bogie has a negative (left side) pickup from the copper strip on the
axle. This is transferred to the chassis at the joint shown on
the right hand side of the photo in the section above. These
bogies are actually from a 2MT, but they are identical to the one
for the 9F and Evening Star.
completeness. The motor, brushes, brush housing, springs and
two different variations of the wiring for the 9f. On the
left, the green wire connects the left hand pickup strip to the
bottom brush cap of the motor. In the photo underneath, there
is no green wire. The bottom brush of the motor picks up its
negative connection by the sprung tab on the brush end cap pressing
against the chassis.
green wire connecting to the bottom brush cap. Left hand
contacts not touching the front two wheels, spring tab on bottom
brush cap is touching the chassis, but the chassis is painted.
Surprising that this loco runs at all really !
Worth checking. The boiler weight is screwed to
the chassis with a long brass screw through the loco body. The
two little studs at the rear should not make contact with the copper
strips - particularly the one on the right ! Normally it will
not do this, but if the contact on the middle wheel has been bent up
Please excuse the photos. Looks like my lens needs a clean.
Maintaining Classic UK Minitrix Locos
The Minitrix trademark is currently owned by Märklin Inc.
Gebr. Märklin & Cie. GmbH, Stuttgarter Straβe 55-57, D-73033 Göppingen,