gyro_gearloose Posted September 19, 2015 Share Posted September 19, 2015 I've got a Mac 250 on the bench for servicing. It's all working perfectly apart from the light sensor. The fixture strikes the lamp via DMX perfectly well, but after about 10 minutes I get 'LERR' on the display. However the lamp remains lit, and the fixture still responds to DMX. I thought Macs shut themselves down when the light sensor detects the lamp going out? Given that my lamp strikes and stays lit, I'm assuming the fault is with the light sensor itself. It's location means it gets very hot, and I understand that it's quite prone to failure. The wiring loom is fine, since it everything works when the lamp is struck and the error message only appears when the fixture has warmed up. If I lamp off via DMX I can re strike the lamp once it has cooled down and it behaves as before I.e no error message until the fixture has warmed up again. My question is what do replace the sensor with? I seem to recall that someone once posted a link to the correct sensor on RS or Farnell, but I can't seem to find it. I have found the TSL251 on Farnells website, but I'm not sure if it's the right part. I know there's one on eBay, but it's four times more expensive than the one from Farnell :) Link to comment Share on other sites More sharing options...
DrV Posted September 19, 2015 Share Posted September 19, 2015 I believe the part you need is a TSL235 Farnell 118-2352. This is a light to frequency sensor. I can't find my notes to verify this but I am pretty sure it is what is used on the 300 so is probably the same on a 250Dave Edit -Just found a post from 2011 when I gave the same info and no-one complained so it must be right :-) Link to comment Share on other sites More sharing options...
Richard CSL Posted September 20, 2015 Share Posted September 20, 2015 It sounds like the lamp is overheating, have you tried a new lamp? and also check the function of the cooling fans, check for dust blocking the airflow. Link to comment Share on other sites More sharing options...
David Lee Posted September 20, 2015 Share Posted September 20, 2015 Drv, that was my post, bit gutted I never followed up on it. You were spot on. Cheers ? Link to comment Share on other sites More sharing options...
gyro_gearloose Posted September 20, 2015 Author Share Posted September 20, 2015 The lamps strikes and stays lit, so I doubt the lamp is over heating. I've completely stripped and rebuilt the Mac, so airflow is not an issue. The fault is with the light sensor, as I've taken it out of the head and it seems to be a bit crispy around the edges. Not surprising given how hot discharge fixtures get. However I can't say I'm surprised that Martin decided to put a component with a maximum working temperature of only 85 degrees so close to a heat source... I'll order a TSL235 from Farnell tomorrow and let you know how it goes. They're offering free postage on all orders at the moment, not just orders over £20 :) Link to comment Share on other sites More sharing options...
gyro_gearloose Posted September 23, 2015 Author Share Posted September 23, 2015 Good news!! I fitted the sensor this morning and I've had the Mac running its demo sequence for about 20 minutes. So far no error messages! Thanks for your help everyone. ...and on a related note: does anyone want to buy 3 Mac 250s? :D Link to comment Share on other sites More sharing options...
gyro_gearloose Posted September 24, 2015 Author Share Posted September 24, 2015 Damn! Spoke too soon. Still getting 'LERR'!! Apparently error messages won't get displayed while running the demo sequence. Having checked the wiring loom and replaced the sensor I'm at a loss to explain why I'm still getting an error message. I hope its not a fault with the motherboard, but I don't know what else it might be. Does anyone else have any ideas? Link to comment Share on other sites More sharing options...
Richard CSL Posted September 24, 2015 Share Posted September 24, 2015 the fixture is probably overheating, but does not shut down as the overheat is not excessive. Try swopping the lamp with another fixture, old lamps burn hotter as they approach end of lamp life. Check to see if all the fans are running. Make sure the airways are clear, oh and check the covers are on properly. Link to comment Share on other sites More sharing options...
gyro_gearloose Posted September 25, 2015 Author Share Posted September 25, 2015 Fixed it!! While I was getting continuity on all three pins of the wiring loom, the loom was actually wired up the wrong way round for the light sensor. My loom was wired 1-1, 2-2, and 3-3, when it should have been wired 1-2, 2-3, and 3-1. The loom came out of my big box of bits, and was probably meant for a Hall sensor which is why it was wired up the wrong way round for a light sensor. Richard, you have twice mentioned that you thought that my error was being caused by over heating. Unlike some other fixtures I've worked on, the original Mac 250 doesn't have a temperature sensor in the head, just the usual thermal trip. I probably should have mentioned earlier that my Mac is an original 250, not one of the later models. Link to comment Share on other sites More sharing options...
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