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Martin Mac 550 LERR


cmgunn

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Hi all,

 

I have 2 Mac 550's that either will attempt to strike but can't or will strike for a few seconds then douses. Both lights have new, known good lamps and fairly new lamp sockets. All of the wiring to and from the ballast is in good visual condition and is secure.

 

I plan on pulling a working 550 this week to swap parts and find the fault. I assume the ballast and power supply is a good place to check. I wanted to see if anyone else had run into this before and what the fix was.

 

 

 

Somewhat related: I have a 3rd 550 with a known bad ballast. Are there any particular components that are common failure points? I've repaired a few switch mode power supplies in PA amps and typically see dried caps or bad transistors as the cause there.

 

Thanks

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It could be a faulty light sensor near the lamp. Basically if the sensor fails then the fixture will always assume the lamp is not on, even if it is. When this happens the fixture cuts power to the lamp circuit so it doesn't keep trying to strike what it thinks is a dead lamp. Since you are using new lamps, and they do actually light up, then I'd have a look at the light sensor.

 

Edit : Heres a link to a post I started two years ago about the light sensors in my Mac 250s. Hopefully some of this information will be of use to you.

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Somewhat related: I have a 3rd 550 with a known bad ballast. Are there any particular components that are common failure points? I've repaired a few switch mode power supplies in PA amps and typically see dried caps or bad transistors as the cause there.

 

I'd imagine your typical electronic ballast is not too much different. I'd think they're just a high power switch mode supply with a current mode control, and an RMS current limit.

 

I'd be looking for the usual suspects, such as dried out electrolytic caps, popped MOSFETs etc. Anything semiconductor, or subject to high working voltages is suspect, and anything that'll dry out in high temperature. Generally not resistors, inductors or ceramic capacitors.

 

If you have access to an oscilloscope, and you know what you're doing, you could poke on to various points and check the wiggly line is correct...

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Thanks for the replies! I pulled a working ballast from another 550 and it is indeed the ballast that has failed in all 3 lights. The replacement ballasts I've seen for sale cost nearly as much as a second hand Mac 700. So it looks like I'll likely be scrapping the lights if I can't fix them.
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  • 4 weeks later...

I have had no success at repairing electronic balasts, so I am curious as to your solution, I also have changed multiple components in a mac 550 only to have it pulse fail at startup.

 

On deeper investigation electronic balasts are incredibly complicated, best option is to trawl ebay for parts or better still send off to Liteparts.com they do repairs on some of them.

 

I also requested a circuit diagram from Schneider the German manufacturer, but they declined on a copyright refusal.

 

So good luck.

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