quick question

timwebb · 16th September 2011, 03:10 AM

whats the best way to discharge the rail before putting the output transistors in? i was thinking about mounting some power resistors to a heat sink for for use as a dummy load and another for current limiting.

Perry Babin · 16th September 2011, 04:25 AM

What amp is this?

Resistors are the best way. 4-10 ohms work well. The lower the resistance, the larger the arc when you discharge them. If you use 25w or greater resistors, you don't need to have them on a heatsink. If you use smaller resistors don't touch the body of the resistor. No matter what resistors you use, don't touch the wire or leads for the resistor.

timwebb · 16th September 2011, 04:31 AM

the audio pipe im workin on. i have to a few hours before i can put the output transistors in cause the current from the rail shorts them out as soon at it touch the pads.

Perry Babin · 16th September 2011, 04:38 AM

If it's out of the sink, you can short across the rail caps with the resistor. If it's in the sink and you want to discharge them before you handle the board, short between the output leg of the rectifiers and any of the secondary windings.

Don't slip and short between the legs of the rectifier because it may burn through the legs on the rectifier.

16th September 2011, 03:10 AM	#1
timwebb diyAudio Member Join Date: Jan 2010 Location: memphis tn	quick question whats the best way to discharge the rail before putting the output transistors in? i was thinking about mounting some power resistors to a heat sink for for use as a dummy load and another for current limiting.

16th September 2011, 04:25 AM	#2
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	What amp is this? Resistors are the best way. 4-10 ohms work well. The lower the resistance, the larger the arc when you discharge them. If you use 25w or greater resistors, you don't need to have them on a heatsink. If you use smaller resistors don't touch the body of the resistor. No matter what resistors you use, don't touch the wire or leads for the resistor. __________________ Links >> Basic Car Audio Amp Repair * Basic Car Audio Electronics * New Site * Basic Switching Power Supply Design * Basic Computer Skills << Links

16th September 2011, 04:38 AM	#4
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	If it's out of the sink, you can short across the rail caps with the resistor. If it's in the sink and you want to discharge them before you handle the board, short between the output leg of the rectifiers and any of the secondary windings. Don't slip and short between the legs of the rectifier because it may burn through the legs on the rectifier. __________________ Links >> Basic Car Audio Amp Repair * Basic Car Audio Electronics * New Site * Basic Switching Power Supply Design * Basic Computer Skills << Links

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16th September 2011, 04:31 AM	#3
timwebb diyAudio Member Join Date: Jan 2010 Location: memphis tn	the audio pipe im workin on. i have to a few hours before i can put the output transistors in cause the current from the rail shorts them out as soon at it touch the pads.

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