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Mac 250 Relay fault

D M Xpressions

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Afternoon all,

I've got a mac 250 with a issue with the lamp relay.


As soon as the fixture is powered up the lamp relay closes. I've checked the automatic lamp on is set to off and all the usual suspect settings.

When un powered I can clearly see the contacts are open. As soon as the power is connected the contact shuts.


I've checked for possible bits on the board shorting tracks and can't see anything.


Any pointers or ideas would be greatfully received.



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The relay is driven by IC307 which is a ULN2803A. You'll probably find that pin 18 is short to 0v (pin 9)




Do you have the PCB diagrams for this board? I've got a local engineering company who does all our PCB repairs. But they like the diagrams so they can check there repairs.

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