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#1
12-20-2002, 07:01 PM
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Electronics Help
I'm trying to replace a fuse. It's the negative rail fuse. I blew it plugging stuff in and out while the power was on and the mute button off. Actually there are four fuses all next to each other in this amplifier. Plus and minus rail fuses and two mosfet fuses per channel. Right next to the fuses there's a bank of big old honkin' 4700 microfarad capacitors... seven total per channel. Everytime I try to replace a fuse the stupid thing sparks and the fuse blows. This happens without the thing being plugged in evfen. I'm thinking the caps are still charged up. How long does it take for them to fully discharge, or do they discharge at all, or is there something else wrong with it?
Kuan 
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#2
12-20-2002, 07:14 PM
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Capacitors will hold a charge almost indefinately, if they are of good quality and in good shape, unless they have something to let them leak down. I'm not up on how they are being used in today's car stereo systems, but back when I was working in an electronics company(20+ years ago) we would always put a hi-ohm resistor across the capacitors to let them leak down over time, something like a 1megohm or more . Not sure if that's the way it's done in car stereo systems now. Are the fuses slo-blo type so they will take a bit more of a spike before they blow? May need to have a way of leaking the capacitors down before putting in a new fuse.
Next, may want to pose this over in the Audio forum. They are a bit more up on how car stereo's are set up now. I'm still kinda old-school on this. 
__________________
past MB rides: '68 220D '68 220D(another one) '67 230 '84 SD Current rides: '06 Lexus RX330 '93 Ford F-250 '96 Corvette '99 Polaris 700 RMK sled 2011 Polaris Assault '86 Yamaha TT350(good 'ol thumper)
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#3
12-20-2002, 07:20 PM
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Nope they're 4amp fast blow. Maybe if I connect up the speakers overnight and then replace them all at once would that work? 4700 microfarad each is quite a lot, multiply that by 7. It's a home amp. I'm one of those electronic hackers btw
I can solder but I know little!Thanks rick! Kuan
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#5
12-21-2002, 08:46 AM
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Yeah they're HUGE! It's tons of storage capacity!
 But yep, they're part of the power supply. I'm going to get some fuses today. I DID think about loading them but thought *****, I don't want to die!Kuan
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