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16th September 2012, 10:15 AM
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#12 |
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diyAudio Member
Join Date: Nov 2003
Location: Louisiana
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Are you sure that those are the right transistors?
Unless this amp uses a drive circuit that's very different from most amps, that transistor should be a PNP transistor. Does this amp use an emitter follower pair (NPN and PNP transistors) for the drivers?
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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 2012, 10:24 AM
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#13 |
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diyAudio Member
Join Date: Jul 2010
Location: Estonia
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It is PNP transistor.2SA1015 is printed on the board on all 4 locations for drivers. Two have their bases connected to pin 9 of 494, two of them to pin 10 of 494.
All collectors tied to ground, emitters connect to gates of two IRFZ44N through a 100 ohm resistor.
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Tools: C1-76 o-scope, Weller WHS40, Mastech MAS830L multimeter, Mastech MY6243 LC meter, 16A supply |
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16th September 2012, 10:53 AM
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#14 |
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diyAudio Member
Join Date: Nov 2003
Location: Louisiana
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I misread the part number. Does the amp use any NPN drivers or does it have a diode connected across the base and emitter of the PNP driver?
If it uses a diode, what is the DC voltage on pins 11 and 12 of the 494?
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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 2012, 11:12 AM
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#15 |
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diyAudio Member
Join Date: Jul 2010
Location: Estonia
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It uses a diode.
Voltage on pins 11 and 12: 9,8 and 8,9V. Voltage across B+ and GND: 10,2V
__________________
Tools: C1-76 o-scope, Weller WHS40, Mastech MAS830L multimeter, Mastech MY6243 LC meter, 16A supply |
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18th September 2012, 11:10 AM
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#16 |
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diyAudio Member
Join Date: Nov 2003
Location: Louisiana
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Why is your power supply producing only 10.2v DC?
What is the amplitude of the square wave on pins 9 and 10? How does that compare to the voltage on the gates of the FETs?
__________________
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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