Mr Steve Posted December 28, 2013 Share Posted December 28, 2013 Hello, I have a MAC 600 which was used on a show 10 days ago. Since then it has FBET and TIER on start up. The tilt system is floppy and offers no resistance when prodded. -Metering the base to yoke wires checks out fine, so the loom is ok-Swapping pan and tilt wires inside, the unit will tilt (and not pan), suggesting the motors are fine.-Swapping drive chips, the fault remains with tilt, suggesting the drive chips are fine. I'm now assuming there is something on the PCB that is dead. Is there an area on the PCB that I need to check / meter out to confirm what the fault is? I would like to get this extra unit back in to action, but if it requires a new board then it's simply not worth it. However I am willing to try any suggestions anyone may have :) Link to comment Share on other sites More sharing options...
johnhuson Posted December 28, 2013 Share Posted December 28, 2013 Unfortunately I can't offer a solution to your exact problem, you've certainly followed similar steps to diagnosis as I would. However if it does turn out to be a PCB issue I can highly recommend Lighting Hospital for PCB repairs, never failed to fix one for us and cheaper than a replacement board especially if you not in a rush for it. Link to comment Share on other sites More sharing options...
gyro_gearloose Posted December 30, 2013 Share Posted December 30, 2013 It will most likely be the resistors used by the chip for measuring the current that have failed and gone high resistance. This is a very common problem with older Martin fixtures, and quite easy to check. Take the chip out of the socket and measure the resistance between pin 10 and either pin 5, 6, 17, or 18. Do the same for pin 13 and 5, 6, 17, or 18. The resistance should be around 0.5Ohm (your meter may not be accurate at such low resistances). Anything too high means that your resistors have failed. Have a look at page 2 of the chip datasheet to work out which pins you need to meter. Swapping out failed resistors is a tricky job if you aren't used to hand-soldering surface mount components, so it might be worth getting the Lighting Hospital to do it. That's what I'll be doing with one of my Mac 250s in the new year. Link to comment Share on other sites More sharing options...
Mr Steve Posted December 30, 2013 Author Share Posted December 30, 2013 Thanks gyro. I will check it out later. I knew I took GCSE electronics for a reason ;) Link to comment Share on other sites More sharing options...
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