Decoder upgrade in GS800

Since the review this loco has been digitally converted too.

The Idea

The idea was to get it digitally controlled. This old version of the Swedish Litt DA loco had 3 separate bulbs at each side, so I thought, wouldn't it be possible to get a separately controlled distant light too? As far as I remember this loco from my childhood, only the two lower lights are lit when in a station; the top light is lit on the line, and also stronger. Right or wrong, this was the behavior I wanted to model.

The equipment

I used a HAMO permanent magnet for SFCM, a Lenz LE130 decoder, and an extra two pole monostable relay. Lenz recommended to use a protecting diode also; when shutting off the current to the coil in the relay, it would otherwise induce a very high voltage which could destroy the decoder. Two small resistors was used to dim the lower lights, I think it was 100 ohm.

A problem to solve was the connection with the lamps. On this model the lamps are inserted from outside when the shell has been mounted, and screwed to fit. From inside a metal plate was pushing and giving the lamp it's power. As the three plates were attached together I must disconnect them in some way. I didn't want to cut any of them, as it would be difficult produce the mechanical force for the lamps in a different way. So I decided to leave the top lamp exactly as it was, the power to this lamp connected to the existing plates. On top of the lower plates I placed a piece of PCB, the board used for soldering electronic components. This has a isolated side, and a cupper side; the cupper of course facing outward and connected to the lamps.

The circuit

The result

The operation was successful. The f1 controls whether dimmed light or distant light is selected, the 'function' control light as usual (could be put off entirely. And the light is always direction dependent. Some errors on the way seems to be compulsory, including this time wrong connection of the relay. Greater problems was the fitting of the motor shield. Had to cut the plastics of the HAMO magnet a bit; I don't know if it would be possible to order another HAMO magnet which fits this old bakelite motor shield, but some surgery with a knife was all that was needed, and now it does it's job.


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