Nicktaylor Posted January 27, 2019 Share Posted January 27, 2019 I became pretty good at mending the original Mac 250s. This is my first time at looking at a Krypton. This unit went from working perfectly to being dead on start up. Checking it on the work bench when plugged in there is momentary power up noise that instantly goes, as if the fan starts then instantly stops. ACtually if left, the power does come on, ie fans start but there is no display and no start up sequence. Does anyone have a sequence to check these out? Its a few years since I did the Whitelight course! Link to comment Share on other sites More sharing options...
timmeh2 Posted January 27, 2019 Share Posted January 27, 2019 Hi First of all, check that the MCB is actually getting power and that the internal fuse hasn't blown All the best Timmeh Link to comment Share on other sites More sharing options...
Nicktaylor Posted January 27, 2019 Author Share Posted January 27, 2019 Hi First of all, check that the MCB is actually getting power and that the internal fuse hasn't blown All the best Timmeh Is that the 20mm fuse by the input IEC socket or further in to the unit? Link to comment Share on other sites More sharing options...
timmeh2 Posted January 28, 2019 Share Posted January 28, 2019 Hi Nick If the IEC fuse has blown nothing will happen; if the fans run but the fixture won't reset then you need to check the internal fuses. The MCB is located in the same place as the original Mac250; I.e underneath the left-hand yoke arm cover. All the bestTimmeh. Link to comment Share on other sites More sharing options...
Nicktaylor Posted January 28, 2019 Author Share Posted January 28, 2019 Its a few years since I was inside one! Thanks for the pointers Link to comment Share on other sites More sharing options...
gyro_gearloose Posted January 28, 2019 Share Posted January 28, 2019 Just to avoid confusion I’m guessing that you meant Main Circuit Board, rather than the more usual Miniature Circuit Breaker? To check the internal voltages, there should be three LEDs near the bottom left of the circuit board in the yoke arm. If they aren’t lit then you’ve got power problems. I can’t remember off the top of my head if the LEDs will light even if the fuse has popped. Link to comment Share on other sites More sharing options...
DrV Posted January 28, 2019 Share Posted January 28, 2019 IIRC the led on the 5volt rail will light with no power connected at all if you move the head around. The emf created by the pan and tilt motors is enough to turn it on. Link to comment Share on other sites More sharing options...
Nicktaylor Posted February 1, 2019 Author Share Posted February 1, 2019 Okay chaps. The 8A fuse was blown on the main circuit board. Sadly it wasnt just old age as the replacement blew. Obviously this means something more critical has failed. Any more pointers please Thanks Nick Link to comment Share on other sites More sharing options...
DrV Posted February 1, 2019 Share Posted February 1, 2019 On the schematic the fuses are shown as F1 3.15AT and F2 2.00AT. Which one is blown? Link to comment Share on other sites More sharing options...
Nicktaylor Posted February 1, 2019 Author Share Posted February 1, 2019 Its the righthand fuse. It was an 8A fuse that I took out! If I had the schematic it would help. I just realised there was on in the back of the handbook. Its the one marked as 6.3 A on my drawing. Without opening another unit, there is red led flashing just by the tilt feedback plug Looking at the rest of the indicators I wonder if that should be lit green or at least the one next to it. Link to comment Share on other sites More sharing options...
indyld Posted February 1, 2019 Share Posted February 1, 2019 Fault finding a blown fuse on a PCB is usually a matter of probing the (dead) board checking for shorts. Obviously after you've found no traces of fried components and eliminated shorting off-board stuff. If a board doesn't include power supply components (particularly MOSFETs) and/or decoupling caps and is mostly chips or other semis, then I look for shorting semi junctions and IC power rails. But to actually get kit back on the shelf, its common practice to swap out the offending board and fiddle with the dead one at ones leisure. There are various ways to speed up the process of finding a board short for the more adventurous involving all manner of stuff like freeze spray and series loads... BTW, I found a schematic that purports to be for the Krytpon at the Elektrotanya archive. Having said that, it shows F1 and F2 as 3.15At and 2At respectively, despite the board layout in the Krypton user manual having the other values. After the 2A fuse 12VAC1 and 12VAC2 seems to be rectified and regulated (Zener and Cap alert!) and feeds the 12v DC rails, with a green LED LD4 indicator. The 3.15A similar, but more caps and 30v for the steppers. Green LD3 is the indicator. Perhaps unplug all the steppers / drivers/ looms to eliminate the possibility of one of them being the cause of a short before doing too much metering. Link to comment Share on other sites More sharing options...
indyld Posted February 1, 2019 Share Posted February 1, 2019 The only Red LED on the schematic I can find is a programming indicator for the FPGA and as such would be a, er, red herring when it comes to blown fuses. It seems odd that part of the circuit on the schematic would result in a flashing LED state though as it looks more like logic. Something doesn't quite add up but again seems unlikely to be related to the original issue but more a discrepancy between what can be seen on the schematic I have and what you find. Link to comment Share on other sites More sharing options...
Nicktaylor Posted February 3, 2019 Author Share Posted February 3, 2019 All looms disconnected and the fuse still blows! The lamp is striking though Link to comment Share on other sites More sharing options...
indyld Posted February 3, 2019 Share Posted February 3, 2019 Did you find the schematic? Is it the F1 part of the circuit that is the issue? If you've narrowed if down to that board I.e everything else is disconnected, then I'd suggest taking it out so you can give it a good examination and poke around with the meter. The PSU elements would be a good starting point. Link to comment Share on other sites More sharing options...
Don Allen Posted February 3, 2019 Share Posted February 3, 2019 The condition of a blown fuse can help with the troubleshooting. A blackened fuse with the fuse wire splattered on the inside indicates a short circuit, usually a bridge rectifier. A fuse that blows quickly indicates an overload on that fuse rail. A fuse that curls apart could just be old age. Link to comment Share on other sites More sharing options...
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