Kenwood KAC-729S

mike49504 · 26th August 2011, 01:34 AM

Got this in for repair..

I replaced 2 defective outputs in the left channel..

Amp will not power up.. No voltage on the 1st leg of the power supply fets..

Any ideas>??

Perry Babin · 26th August 2011, 01:48 AM

Post the voltage on the 494.

Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:
Pin 11:
Pin 12:
Pin 13:
Pin 14:
Pin 15:
Pin 16:

mike49504 · 26th August 2011, 02:02 AM

Pin 1: 0
Pin 2: 4.98
Pin 3: 0.07
Pin 4: 0.31
Pin 5: 1.66
Pin 6: 3.66
Pin 7: 0
Pin 8: 13.83
Pin 9: 5.12
Pin 10: 5.11
Pin 11: 13.83
Pin 12: 13.83
Pin 13: 4.98
Pin 14: 4.98
Pin 15: 4.98
Pin 16: 0

Perry Babin · 26th August 2011, 02:17 AM

You should have ~5v on the gates of the FETs.

mike49504 · 26th August 2011, 02:26 AM

Ok i fixed that one i had a broken solder connection...

I have another one in for repair also..

when i power the second one up it draws excessive current...

If i only hook power and ground up it will draw excessive current also..

I removed the fets and they all test fine..

Any ideas?

Perry Babin · 26th August 2011, 02:29 AM

Power it up through the limiter and measure the DC voltage on the power supply FETs (black on leg 3, red on leg 1).

mike49504 · 26th August 2011, 02:39 AM

I get -3.38 volts on all of them

Perry Babin · 26th August 2011, 02:50 AM

It can't be negative. Are the meter leads in the correct locations in the meter?

mike49504 · 26th August 2011, 02:57 AM

Sorry my mistake.. I get 3.38 volts

Perry Babin · 26th August 2011, 03:23 AM

Did you have your probes backwards?

If so, did you have them backwards when you read 0v on the gates?

26th August 2011, 01:34 AM	#1
mike49504 diyAudio Member Join Date: Sep 2006	Kenwood KAC-729S Got this in for repair.. I replaced 2 defective outputs in the left channel.. Amp will not power up.. No voltage on the 1st leg of the power supply fets.. Any ideas>??

26th August 2011, 01:48 AM	#2
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Post the voltage on the 494. Pin 1: Pin 2: Pin 3: Pin 4: Pin 5: Pin 6: Pin 7: Pin 8: Pin 9: Pin 10: Pin 11: Pin 12: Pin 13: Pin 14: Pin 15: Pin 16: __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

26th August 2011, 02:17 AM	#4
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	You should have ~5v on the gates of the FETs. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

26th August 2011, 02:29 AM	#6
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Power it up through the limiter and measure the DC voltage on the power supply FETs (black on leg 3, red on leg 1). __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

26th August 2011, 02:50 AM	#8
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	It can't be negative. Are the meter leads in the correct locations in the meter? __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links


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26th August 2011, 02:02 AM	#3
mike49504 diyAudio Member Join Date: Sep 2006	Pin 1: 0 Pin 2: 4.98 Pin 3: 0.07 Pin 4: 0.31 Pin 5: 1.66 Pin 6: 3.66 Pin 7: 0 Pin 8: 13.83 Pin 9: 5.12 Pin 10: 5.11 Pin 11: 13.83 Pin 12: 13.83 Pin 13: 4.98 Pin 14: 4.98 Pin 15: 4.98 Pin 16: 0

26th August 2011, 02:26 AM	#5
mike49504 diyAudio Member Join Date: Sep 2006	Ok i fixed that one i had a broken solder connection... I have another one in for repair also.. when i power the second one up it draws excessive current... If i only hook power and ground up it will draw excessive current also.. I removed the fets and they all test fine.. Any ideas?

26th August 2011, 02:39 AM	#7
mike49504 diyAudio Member Join Date: Sep 2006	I get -3.38 volts on all of them

26th August 2011, 02:57 AM	#9
mike49504 diyAudio Member Join Date: Sep 2006	Sorry my mistake.. I get 3.38 volts

26th August 2011, 03:23 AM	#10
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Did you have your probes backwards? If so, did you have them backwards when you read 0v on the gates? __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

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