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Offline johnmarklin  
#1 Posted : 24 February 2018 17:23:34(UTC)
johnmarklin

Ireland   
Joined: 31/03/2011(UTC)
Posts: 171
Location: Ireland
Good afternoon fellow Marklin Gauge 1 enthusiasts. I am in need of assistance with a problem I have with my class 78.

When I try to change the direction of travel for the locomotive the locomotive leaps forward at high speed and continues traveling in the same direction and the relay just buzzes when I try to change direction. I have adjusted the relay spring tension but this makes no difference. The relay works perfectly when wired directly without the circuit board. I have replaced the relay with another relay but the problem is still the same.

What is the function of the circuit board and is it possible to get a replacement/repair board anywhere. I have checked the Marklin shop but this part is no longer available.

Your thoughts, observations or recommendations would be appreciated.

John
Offline Markus Schild  
#2 Posted : 24 February 2018 22:25:49(UTC)
Markus Schild

Germany   
Joined: 14/01/2006(UTC)
Posts: 1,802
Location: Wurttemberg
Hi John,

The circuit board should prevent the loco from jumping while switching and switches the lights.

If it's defective I would replace the circuit and the relay with a Uhlenbrock electronic switch #55700. If you find sometimes the original spares, you can build it back.

Regards

Markus
thanks 1 user liked this useful post by Markus Schild
Offline johnmarklin  
#3 Posted : 26 February 2018 12:05:47(UTC)
johnmarklin

Ireland   
Joined: 31/03/2011(UTC)
Posts: 171
Location: Ireland
Markus,

Thank you for your suggestion.

Before purchasing the Uhlenbrock unit I decided to test the circuit board. The circuit board works, (the mounted relay clicks) and the circuit board delivers a pulse of 25.4 volts when I reverse current at the transformer. I have replaced the relay with another relay which works perfectly without the spring but with the spring attached the relay buzzes. With a lot of adjustment I have managed to improve the situation. I have reduced the tension on the the spring as much as is possible and I also stretched the spring. The result is reasonably satisfactory but not entirely to my liking.

Do the electro magnets of a relay become less powerful over time and if so what is the reason for so?

Best wishes,

John
Offline Markus Schild  
#4 Posted : 26 February 2018 12:12:58(UTC)
Markus Schild

Germany   
Joined: 14/01/2006(UTC)
Posts: 1,802
Location: Wurttemberg
Hi John,

The relays don't get weak. I have some which work perfect for 60 years. As usual at old electronics I would suspect the condenser on the board. These get weak with the years. More if only used rarely. If the specification is readable I would replace it first.

Regards

Markus
thanks 1 user liked this useful post by Markus Schild
Offline johnmarklin  
#5 Posted : 26 February 2018 13:23:30(UTC)
johnmarklin

Ireland   
Joined: 31/03/2011(UTC)
Posts: 171
Location: Ireland
Markus,

Thank you for your message and information. The condenser is the one component that I did suspect. I will work on it later and report on progress.

Best wishes,

John
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