Kenwood KAC 8101D

mike49504 · 14th May 2010, 07:18 PM

I have this amp in for repair. When i opened the amp up and started checking stuff out I found the following .

10 ohm resistors connected to leg 1 of the outputs were Defective.

Q53 (C3940) to be defective
Q22 (A1123) to be defective.
Q63,Q64 A1266 to be defective.

Also D53 is a diode looks like a zener it has 153 on it nothing else Do you know what diode this is??
I put a 1n4148 in its spot to test the amp.

The problem im having now is the gain has to be fully counter clockwise and the amp will produce sound but very quiet.

If i start turning the gain up the amp makes the speaker flutter like crazy like im getting 100 volts to it. I put my test leads on the output and when the amp does this i dont have any Dc on the outputs.

Wondering what might cause this?

Perry Babin · 14th May 2010, 07:55 PM

D53 is a 15v Zener diode. Using the 1N4148 likely allowed high voltage to reach the op-amps and may have caused significant damage. You'll need to replace it with the correct part and troubleshoot from there.

The noise sounds like the amp or signal source has an open shield ground.

mike49504 · 14th May 2010, 07:58 PM

What part number will work for the diode?

Perry Babin · 14th May 2010, 08:16 PM

If it was the size of a 1N4148, a 1N5245 would be the sub.

Looking at the schematic again, this appears to be for the driver supply voltage so the op-amp wouldn't have likely been damaged.

mike49504 · 14th May 2010, 08:26 PM

How do i check for an open shield ground on this amp?

Perry Babin · 14th May 2010, 10:26 PM

On this amp, the only shield ground connection likely to fail would be at the RCA jacks. Confirm that you have continuity between the shield (of both the left and right jacks) and the circuit board where the shield terminal on the jack is soldered to the board. Move the jack around while checking continuity in case the connection is intermittent. Don't have any RCAs plugged into the jacks.

14th May 2010, 07:18 PM	#1
mike49504 diyAudio Member Join Date: Sep 2006	Kenwood KAC 8101D I have this amp in for repair. When i opened the amp up and started checking stuff out I found the following . 10 ohm resistors connected to leg 1 of the outputs were Defective. Q53 (C3940) to be defective Q22 (A1123) to be defective. Q63,Q64 A1266 to be defective. Also D53 is a diode looks like a zener it has 153 on it nothing else Do you know what diode this is?? I put a 1n4148 in its spot to test the amp. The problem im having now is the gain has to be fully counter clockwise and the amp will produce sound but very quiet. If i start turning the gain up the amp makes the speaker flutter like crazy like im getting 100 volts to it. I put my test leads on the output and when the amp does this i dont have any Dc on the outputs. Wondering what might cause this?

14th May 2010, 07:55 PM	#2
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	D53 is a 15v Zener diode. Using the 1N4148 likely allowed high voltage to reach the op-amps and may have caused significant damage. You'll need to replace it with the correct part and troubleshoot from there. The noise sounds like the amp or signal source has an open shield ground. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

14th May 2010, 08:16 PM	#4
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	If it was the size of a 1N4148, a 1N5245 would be the sub. Looking at the schematic again, this appears to be for the driver supply voltage so the op-amp wouldn't have likely been damaged. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

14th May 2010, 10:26 PM	#6
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	On this amp, the only shield ground connection likely to fail would be at the RCA jacks. Confirm that you have continuity between the shield (of both the left and right jacks) and the circuit board where the shield terminal on the jack is soldered to the board. Move the jack around while checking continuity in case the connection is intermittent. Don't have any RCAs plugged into the jacks. __________________ 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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14th May 2010, 07:58 PM	#3
mike49504 diyAudio Member Join Date: Sep 2006	What part number will work for the diode?

14th May 2010, 08:26 PM	#5
mike49504 diyAudio Member Join Date: Sep 2006	How do i check for an open shield ground on this amp?

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