Mr Steve Posted November 21, 2013 Author Share Posted November 21, 2013 Doom. Chip swapped, with heatsink. Board back in. The unit displays RST as normal, but there is no power to any of the motors, no wheels move or calibrate (they are freely movable with no resistance). The fans spin up though. I'm guessing something on the motherboard is toast? Any ideas? *after a while it will scroll the various errors as it can't calibrate any of the attributes etc Lamp will strike/douse off the manual menu. Loom meters out from base to head. UPDATEAny driver chip in the pan or tilt driver position causes fuse F601 (T5AL) to pop. With the chips missing, the thing will home all colours etc. Does this suggest a short on the PCB / chip sockets? The board is fairly mucky... Link to comment Share on other sites More sharing options...
timsabre Posted November 21, 2013 Share Posted November 21, 2013 Does the fuse blow if you unplug all the motor wires? This would help you determine if it is a wiring/motor problem or a PCB problem Link to comment Share on other sites More sharing options...
Mr Steve Posted November 21, 2013 Author Share Posted November 21, 2013 I've had a proper dense moment. The 3775 chips have their dimple upwards, and the 3772s dimple down, so I had flipped the orientation of the driver causing the motor fuse to blow. Slightly embarrassing....but it now works. Link to comment Share on other sites More sharing options...
gyro_gearloose Posted November 21, 2013 Share Posted November 21, 2013 Also be sure to check the legs on the pan/tilt driver chips. It is very easy for one or more pins to miss their holes in the socket and end up getting bent. If a leg is bent and touching something it shouldn't, it could easily cause all sorts of issues. It could also be the current sensing resistors for the pan/tilt motors that have failed. This would lead to the driver chip trying to pass too much current to the motor, which would in turn kill the chip and the fuse. I'm fairly certain that the pan/tilt motors are fed from a different supply to all the other motors as they need a higher voltage. Have a look at the datasheet for the driver chip. It will tell you where the resistors connect to the chip. Remove the chip, measure the resistance of the current-sensing resistors on the motherboard, and compare with a known working unit. On a Mac 250 there are three 1.5Ohm resistors connected in parallel to give a combined resistance of 0.5Ohms. There are two sets of resistors per chip, one set per motor winding, so be sure to check both. Link to comment Share on other sites More sharing options...
timsabre Posted November 21, 2013 Share Posted November 21, 2013 It could also be the current sensing resistors for the pan/tilt motors that have failed. This would lead to the driver chip trying to pass too much current to the motor, which would in turn kill the chip and the fuse. I'm fairly certain that the pan/tilt motors are fed from a different supply to all the other motors as they need a higher voltage. The most common sense resistor fault is that they go open circuit which leads to no current in the motor. However if they go short circuit, then overcurrent happens as you say. Link to comment Share on other sites More sharing options...
Mr Steve Posted November 22, 2013 Author Share Posted November 22, 2013 Thanks everyone. The fixture is working, plus I have a schematic for future reference....should I try and repair any further wrecks. Link to comment Share on other sites More sharing options...
Jivemaster Posted November 22, 2013 Share Posted November 22, 2013 Overheating in intelligent lights is sometimes caused by poor cooling, blocked airways, dirty or inadequate fans are prime causes Link to comment Share on other sites More sharing options...
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