LGB 20621 diesel (Schoema?) deceased

[KeithT]

Probably foolishly, I offered to look at an LGB 202621 which inexplicably 'died'. It was purely on the understanding that I would check for mechanical faults or a loose wire.
It was fitted with a chip several years ago and had run happily since.
Whatever the chip was the loco never had the lights operative since it was fitted.
On opening up the loco I found a dogs breakfast of wiring and an ominous pong from the Bachmann 35-556 chip. An online check shows this to be a 2 function 1A chip designed for Hornby/Bachman. I suppose it is surprising it lasted as long as it did.
I have established that the motor runs OK with a direct connection.
The existing moter connections are green and black and the pins on the motor block are marked WS, BR and GR although the wires have been mixed up with different coloured ones from the chip..
I have been asked if I can return the loco to analogue &: so my query is how do I connect up to achieve this, ideally with working lights? The front and rear lights have what appear to be the original Brown and Black wires connected.
Any help gratefully accepted 'cos as I have said on other occasions "I don't do electronics"!
(I could not find a diagram for this loco on the Champex-Linden site)

 

[Gizzy]

I think this is a 3 wire job from your description as there does not seem to be a yellow wire.

A photo of the chassis may help us with re-wiring....

 

[KeithT]

OK will do.
Yes it is 3 wire.

 

[Gizzy]

If needs must Keith, I'll have a look at mine tomorrow, and take a photo as well, so that you can compare them.

I know mine is also an old 3 wire one.

One of the 3 wires is common to the motor and the skates, but I can't remember which? A multimeter will help you check this....

 

[KeithT]

Not sure if this helps....

The wires to the pins were in a complete kaleidoscope of varying colours along their lengths. Difficult to know what they were originally. The brown wire was not connected.

 

[whatlep]

OK will do.
Yes it is 3 wire.

Keith, as you're probably aware the white in a 3-pin gearbox is (or should be) a common connection between track and motor. On the other side, brown goes to the track and green to the motor (both -ve side). Now if this has been working in DCC mode, presumably there is an extra wire coming from the motor (the equivalent of the yellow wire in a 4-pin gearbox)? That can be connected to the white wire.

As to getting the loco working, for simple motion, just connecting the brown/green wires and white/yellow(?) wires should get things moving. Getting lights working depends on whether you still have the original mainboard for the Schoema. If so, try fixing the motor/ track wires white&yellow(?)/green/brown to the three pins marked w/g/b and the lighting wires to the two remaining pins (he said hopefully!)

 

[whatlep]

Not sure if this helps....

Yes it does!
Unsolder both the wires currently leading from the motor. Reassemble so that the motor's metal "prongs" make contact with the outer pins. The pin nearest the camera is now the white/yellow wire referred to in my previous post - in other words the common wire connected motor and track +ve. The other two pins are (inner) brown wire for track -ve and (farthest from camera) green for motor -ve.

 

[KeithT]

Ah, no white wire and no mainboard!!!!!

 

[KeithT]

Not sure if this helps....

Yes it does!
Unsolder both the wires currently leading from the motor. Reassemble so that the motor's metal "prongs" make contact with the outer pins. The pin nearest the camera is now the white/yellow wire referred to in my previous post - in other words the common wire connected motor and track +ve. The other two pins are (inner) brown wire for track -ve and (farthest from camera) green for motor -ve.

Saw this after I had posted my previous one.
I have got to go out (and be sociable I am told) so will probably have go at what you suggest tomorrow.
Many thanks

 

[Philbahn]

Keith the wire nearest the camera looks to have been trapped. Has it?

 

[whatlep]

Ah, no white wire and no mainboard!!!!!

OK - lights a problem!!
To get the loco working, follow the unsoldering advice in my second post and connect the two pins which are on the far side of the gearbox in your photo. You now have a working loco without lights.

I'll have a look for mainboard options from Modell-land in Germany and repost. Those with more electrical and soldering skill than I may be able to come up with a cheap solution involving diodes.

 

[KeithT]

Ah, no white wire and no mainboard!!!!!

OK - lights a problem!!
To get the loco working, follow the unsoldering advice in my second post and connect the two pins which are on the far side of the gearbox in your photo. You now have a working loco without lights.

I'll have a look for mainboard options from Modell-land in Germany and repost. Those with more electrical and soldering skill than I may be able to come up with a cheap solution involving diodes.

Peter don't worry about the lights. My record with soldering diodes does not bear scrutiny. The owner of the loco will be v happy if it just goes.

 

[Gizzy]

Keith the wire nearest the camera looks to have been trapped. Has it?

Both the green and the black wires by the look of it....

 

[Gizzy]

Keith,

I've looked at your picture above, and it seems that yellow tape has been wrapped around the wires, insulating the motor contacts from the pins?

Remove the tape if so and, connect the wires to the same pins.

The pins I've marked with a yellow circle must be the pickup pins, and I suspect therefore the Shoema was formerly a four wire one before its DCC 'conversion'!

You could simply link each pair of pins each side together to get the loco working.

Similarly, you could wire the lights to these pins, and you'll have a working loco, with lights and no need for a pcb....

 

[whatlep]

Saw this after I had posted my previous one.
I have got to go out (and be sociable I am told) so will probably have go at what you suggest tomorrow.
Many thanks

You have my sympathies about enforced sociability!

Checked Modell-land and they are not featuring any mainboards suitable for 3-pin gearboxes and a small loco like the Schoema, but a bit of lateral thinking suggests an alternative if you don't want to start soldering diodes. Simply buy two of Piko's 36013 LEDs with factory-fitted resistors suitable for analogue voltage. Gaugemaster have them in stock at £6 each which is rather expensive, but at least one postage option is free (Dragon G scale ask £4.70 but are showing out of stock as I write).

If you go that way, connections are very simple. Connect your motor/track leads to a 2-way connector block of your choice inside the loco body. Then attach the first LED. Check if it illuminates in the desired direction. If not, reverse the LED connections at the connector block. Attach the 2nd LED with its wires the other way round to the first.

 

[KeithT]

Yes the wires had been trapped but not bared although one of the wires from the chip had a bare section which might have been responsible for the loco dying. Also, the brown wire to the lights had one end loose and perhaps that shorted out. Whatever, the chip is dead so long live analogue!!
( I have been spared 'sociability for a few minutes as 'someone' got the time wrong.....)

 

[KeithT]

I now have a working Schoema but I found that I had to connect the motor wires to the isolated pin and to the inner one to get power to the motor. The other outer pin is dead and does not appear to be connected to anything at its other end.
Initially, I wired the lights in so that both front and back were 'on' together but they seriously overheated. I assume that they are not intended to run at the full 18V and would have had their voltage reduced by the original board; the bulbs are the yellow screw-in type.

Thanks to all for the advice.

The only remaining problem is that I have two small screws left over.....:wits:
I can't understand it because everything is rock solid.

 

[yb281]

The only remaining problem is that I have two small screws left over.....:wits:
I can't understand it because everything is rock solid.

I wouldn't worry too much Keith, LGB tend to go a bit OTT when it comes to holding the body to the chassis - all part of their "bomb proofness".
When I recently converted my Corpet to battery RC, I found that the body was solid as a rock when held in place by 4 screws while I worked on it. If I remember right, another 8 are used when everything is in place!!

 

[Neil Robinson]

Initially, I wired the lights in so that both front and back were 'on' together but they seriously overheated. I assume that they are not intended to run at the full 18V and would have had their voltage reduced by the original board; the bulbs are the yellow screw-in type.

If they are genuine LGB the yellow screw-in type are 18V.
If they are running too hot and/or bright you could always wire two or three in series.

 

[KeithT]

The only remaining problem is that I have two small screws left over.....:wits:
I can't understand it because everything is rock solid.

I wouldn't worry too much Keith, LGB tend to go a bit OTT when it comes to holding the body to the chassis - all part of their "bomb proofness".
When I recently converted my Corpet to battery RC, I found that the body was solid as a rock when held in place by 4 screws while I worked on it. If I remember right, another 8 are used when everything is in place!!

Update that to 4 screws!!1
I will investigate as I am going open it up again to rewire the lights a s suggested by Neil.