PPI PC4800

mike49504 · 16th February 2011, 12:05 AM

I got this amp in for repair and checked all outputs they seem fine. I checked all emitter resistors they check fine.

I also check the J111's they seem fine and reflowed the solder on the large transistors on the driver cards.

I still have distorted audio on the front right channel.

Any ideas where to go from here?

Perry Babin · 16th February 2011, 11:49 AM

Confirm that you have the same DC supply voltage (both positive and negative) on the emitters of the large SMD driver transistors on all of the boards.

mike49504 · 16th February 2011, 02:12 PM

Yes i have both positive and negative DC voltages on the emitters of all large transistors on the driver boards

Perry Babin · 16th February 2011, 02:17 PM

Is the signal clean going into the driver board (pin 3)?

mike49504 · 16th February 2011, 02:25 PM

Yes the signal looks the same as on the other 3 driverboards.

Perry Babin · 16th February 2011, 02:29 PM

What work has been done to this amp?

mike49504 · 16th February 2011, 02:33 PM

Only thing i did to this amp was replace the 10 ohm 1 watt resistors that sit behind the rca inputs that are on the input board.

Perry Babin · 16th February 2011, 02:38 PM

Drive a sine wave into the amp and post a photo of the distorted waveform (preferably with a speaker connected).

mike49504 · 16th February 2011, 03:00 PM

Scope set to 5ms .1 volts div and a 250hz sine wave

Perry Babin · 16th February 2011, 03:21 PM

What is the circuit board designation for one of the outputs in this channel?

16th February 2011, 12:05 AM	#1
mike49504 diyAudio Member Join Date: Sep 2006	PPI PC4800 I got this amp in for repair and checked all outputs they seem fine. I checked all emitter resistors they check fine. I also check the J111's they seem fine and reflowed the solder on the large transistors on the driver cards. I still have distorted audio on the front right channel. Any ideas where to go from here?

16th February 2011, 11:49 AM	#2
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Confirm that you have the same DC supply voltage (both positive and negative) on the emitters of the large SMD driver transistors on all of the boards. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

16th February 2011, 02:17 PM	#4
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Is the signal clean going into the driver board (pin 3)? __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

16th February 2011, 02:29 PM	#6
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	What work has been done to this amp? __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

16th February 2011, 02:38 PM	#8
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Drive a sine wave into the amp and post a photo of the distorted waveform (preferably with a speaker connected). __________________ 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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16th February 2011, 02:12 PM	#3
mike49504 diyAudio Member Join Date: Sep 2006	Yes i have both positive and negative DC voltages on the emitters of all large transistors on the driver boards

16th February 2011, 02:25 PM	#5
mike49504 diyAudio Member Join Date: Sep 2006	Yes the signal looks the same as on the other 3 driverboards.

16th February 2011, 02:33 PM	#7
mike49504 diyAudio Member Join Date: Sep 2006	Only thing i did to this amp was replace the 10 ohm 1 watt resistors that sit behind the rca inputs that are on the input board.

16th February 2011, 03:21 PM	#10
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	What is the circuit board designation for one of the outputs in this channel? __________________ 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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