Pac-Fan
New member
Why do MCR boards (Tron, Kick/man) smoke the +12V 10uH coil (L116)?
This is about the 3rd or 4th time this has happened, and there is no consistency to the cause.
I was fixing up a Tron with original PS, metered all of the voltages, checked the ribbons, connected power and suddenly L116, a coil on the +12V line on the Super CPU board smoked. This is the last sealed one on the row that usually looks like a black bullet (similar to a large diode but with a tapered end), or a super-sized cyan-colored resistor-looking package. Not the open face wire wound coils on the +5V lines.
Years earlier, one or two of Kick/Kickman boards I was testing on a switcher had the +12V line toast the coil as well.
Then, when benchtesting a new batch of Kick boards, along with the Tron board that toasted itself in the machine, with a new switcher, one of them also promptly toasted the +12V coil.
All voltages, interconnect cables, etc.. have been double and triple checked. I am completing bench testing of the boards without the +12V line connected now to prevent any others from being damaged. Am scared to ever reconnect it. The boards (video output only at least) appear unaffected after the damage? What explicitly does the board use the +12V for -- I haven't had time to trace through the schems/board yet.
Interestingly, the two caps leading to ground along side the coil (.01uF C121/C122) had been clipped off the board on this line only--just on the Tron board.
This is about the 3rd or 4th time this has happened, and there is no consistency to the cause.
I was fixing up a Tron with original PS, metered all of the voltages, checked the ribbons, connected power and suddenly L116, a coil on the +12V line on the Super CPU board smoked. This is the last sealed one on the row that usually looks like a black bullet (similar to a large diode but with a tapered end), or a super-sized cyan-colored resistor-looking package. Not the open face wire wound coils on the +5V lines.
Years earlier, one or two of Kick/Kickman boards I was testing on a switcher had the +12V line toast the coil as well.
Then, when benchtesting a new batch of Kick boards, along with the Tron board that toasted itself in the machine, with a new switcher, one of them also promptly toasted the +12V coil.
All voltages, interconnect cables, etc.. have been double and triple checked. I am completing bench testing of the boards without the +12V line connected now to prevent any others from being damaged. Am scared to ever reconnect it. The boards (video output only at least) appear unaffected after the damage? What explicitly does the board use the +12V for -- I haven't had time to trace through the schems/board yet.
Interestingly, the two caps leading to ground along side the coil (.01uF C121/C122) had been clipped off the board on this line only--just on the Tron board.
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