Infinity amp problem

HiVi Guy · 7th January 2010, 02:44 AM

Hello, I have a Infinity REF475a I got for Christmas. I was testing it and discovered one of the channels puts out a really scratchy sound. The music played through the channel is really distorted. What could cause this? When this happens my personal diagnosis is some DC went into the output and partially fried the output transistors. However, I thought this amp had protection from various faults like this. I was quite careful when hooking it up. Thanks for any replies.

Perry Babin · 7th January 2010, 03:01 AM

Have you tried the following?:

Swapping RCAs to determine if the problem is related to the input signal?

Swapping speaker wires at the amp's speaker terminals to see if it's a wiring/speaker problem?

Moving all controls/switches through their entire range to see if the problem gets better/worse?

HiVi Guy · 7th January 2010, 03:18 AM

Yes sir, I tried all of that. All of the other channels work fine. Tried A different set of cables and a different source and it still does not work properly.

Perry Babin · 7th January 2010, 03:53 AM

Do want to try to repair the amp?

If so, do you have a scope?

HiVi Guy · 7th January 2010, 04:21 AM

The amp is still under warranty. I am going to contact the seller to see what he says. I will probably ship the amp back just to learn they will not warranty it for some stupid reason. In which case I will repair it myself. By that time, with all of the shipping cost I could have bought another amp.

I am an electronics engineering student and I have fixed a few amps for classmates of mine. However, I do not own a scope of my own nor do I have access to one at the moment. I am currently reading the links in your signature. I know a guy named Paul Babin who lives in Louisiana. Thanks for your help.

HiVi Guy · 07:16 PM

I am going to try to fix the amp myself. However, I cannot seem to find a schematic online. I think some DC from the power supply went into the RCA for the channel that does not work. I am opening the amp right now. What do I need to check for? I do not own a scope, but I do have a multimeter.

Perry Babin · 21st January 2010, 07:36 PM

Email me if you want the service manual.

babin_perry@yahoo.com

HiVi Guy · 21st January 2010, 07:53 PM

You have mail from Jason-Martin@live.com

HiVi Guy · 26th February 2010, 01:48 AM

I finally got some time to disassemble the amplifier.

I took out the transistors for the channel that is not working, and the diode setting on my meter says the following:

TIP35C
C=503
E=504

TIP36C
C=530
E=531

Perry Babin · 26th February 2010, 02:07 AM

Do they both read open when you check from collector to emitter?

7th January 2010, 02:44 AM	#1
HiVi Guy diyAudio Member Join Date: Oct 2009	Infinity amp problem Hello, I have a Infinity REF475a I got for Christmas. I was testing it and discovered one of the channels puts out a really scratchy sound. The music played through the channel is really distorted. What could cause this? When this happens my personal diagnosis is some DC went into the output and partially fried the output transistors. However, I thought this amp had protection from various faults like this. I was quite careful when hooking it up. Thanks for any replies.

7th January 2010, 03:01 AM	#2
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Have you tried the following?: Swapping RCAs to determine if the problem is related to the input signal? Swapping speaker wires at the amp's speaker terminals to see if it's a wiring/speaker problem? Moving all controls/switches through their entire range to see if the problem gets better/worse? __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

7th January 2010, 03:53 AM	#4
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Do want to try to repair the amp? If so, do you have a scope? __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

21st January 2010, 07:12 PM	#6
HiVi Guy diyAudio Member Join Date: Oct 2009	I am going to try to fix the amp myself. However, I cannot seem to find a schematic online. I think some DC from the power supply went into the RCA for the channel that does not work. I am opening the amp right now. What do I need to check for? I do not own a scope, but I do have a multimeter. Last edited by HiVi Guy; 21st January 2010 at 07:16 PM.

21st January 2010, 07:36 PM	#7
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Email me if you want the service manual. babin_perry@yahoo.com __________________ 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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7th January 2010, 03:18 AM	#3
HiVi Guy diyAudio Member Join Date: Oct 2009	Yes sir, I tried all of that. All of the other channels work fine. Tried A different set of cables and a different source and it still does not work properly.

7th January 2010, 04:21 AM	#5
HiVi Guy diyAudio Member Join Date: Oct 2009	The amp is still under warranty. I am going to contact the seller to see what he says. I will probably ship the amp back just to learn they will not warranty it for some stupid reason. In which case I will repair it myself. By that time, with all of the shipping cost I could have bought another amp. I am an electronics engineering student and I have fixed a few amps for classmates of mine. However, I do not own a scope of my own nor do I have access to one at the moment. I am currently reading the links in your signature. I know a guy named Paul Babin who lives in Louisiana. Thanks for your help.

21st January 2010, 07:53 PM	#8
HiVi Guy diyAudio Member Join Date: Oct 2009	You have mail from Jason-Martin@live.com

26th February 2010, 01:48 AM	#9
HiVi Guy diyAudio Member Join Date: Oct 2009	I finally got some time to disassemble the amplifier. I took out the transistors for the channel that is not working, and the diode setting on my meter says the following: TIP35C C=503 E=504 TIP36C C=530 E=531

26th February 2010, 02:07 AM	#10
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Do they both read open when you check from collector to emitter? __________________ 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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