Pioneer KEX-M900 troubleshooting - Page 2

vincegironda · 23rd November 2020, 02:57 PM

I also tested the outputs on IC760 and IC765

IC760 has clean audio on pin 25, and low distorted audio on pin 19

IC765 has no audio on pin 25 or pin 19

Perry Babin · 23rd November 2020, 05:09 PM

What page is IC703 on?

If you have audio on the output terminals of 764, that's what's important. If the op-amp is working properly, you won't see signal on the inverting input unless you go back to the resistor in series with that input.

Does heating/cooling any of the DACs make a difference?

vincegironda · 23rd November 2020, 06:08 PM

thanks Perry IC703 is on page marked 19, fig 13

I'll try heating and cooling the DACs and let you know if it helps

vincegironda · 23rd November 2020, 06:21 PM

Heating and cooling made no difference

vincegironda · 23rd November 2020, 06:45 PM

Quote:

Originally Posted by Perry Babin

What page is IC703 on?

If you have audio on the output terminals of 764, that's what's important. If the op-amp is working properly, you won't see signal on the inverting input unless you go back to the resistor in series with that input.

Does heating/cooling any of the DACs make a difference?

So is it safe to assume if IC 764 has audio on the output terminals then the problem lies further along the circuit after IC764?

Perry Babin · 23rd November 2020, 10:47 PM

You have one good channel, correct? Isn't the one good channel?

I'd think the problem is before the op-amps.

You might try injecting signal into pin 5 of the other 3 op-amps to see if it passes cleanly.

vincegironda · 23rd November 2020, 11:10 PM

Correct, I have clean signal in one channel only

Can I pick up the signal from IC 764 and inject into the other ic's?

If yes do I pic up the 764 input signal or output signal?

Perry Babin · 23rd November 2020, 11:14 PM

Pin 1 of IC764 to pin 5 of the other op-amps. You could use an external signal source as well.

vincegironda · 23rd November 2020, 11:15 PM

OK will give it a go, thank you

vincegironda · 24th November 2020, 10:07 AM

So Perry I did as you suggested and injected signal from 764 to the other 3 DACs and found

761 produced clean audio
762 produced clean audio

763 no audio and it muted the signal from 764.

Looks like 762 is defective, shall I remove it from the circuit and see what happens?

23rd November 2020, 05:09 PM	#12
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	What page is IC703 on? If you have audio on the output terminals of 764, that's what's important. If the op-amp is working properly, you won't see signal on the inverting input unless you go back to the resistor in series with that input. Does heating/cooling any of the DACs make a difference? __________________ Anyone who purchased the repair tutorial, email me (babin_perry@yahoo.com) if you want to download the latest version.

23rd November 2020, 10:47 PM	#16
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	You have one good channel, correct? Isn't the one good channel? I'd think the problem is before the op-amps. You might try injecting signal into pin 5 of the other 3 op-amps to see if it passes cleanly. __________________ Anyone who purchased the repair tutorial, email me (babin_perry@yahoo.com) if you want to download the latest version.

23rd November 2020, 11:14 PM	#18
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Pin 1 of IC764 to pin 5 of the other op-amps. You could use an external signal source as well. __________________ Anyone who purchased the repair tutorial, email me (babin_perry@yahoo.com) if you want to download the latest version.

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23rd November 2020, 02:57 PM	#11
vincegironda diyAudio Member Join Date: Sep 2013	I also tested the outputs on IC760 and IC765 IC760 has clean audio on pin 25, and low distorted audio on pin 19 IC765 has no audio on pin 25 or pin 19

23rd November 2020, 06:08 PM	#13
vincegironda diyAudio Member Join Date: Sep 2013	thanks Perry IC703 is on page marked 19, fig 13 I'll try heating and cooling the DACs and let you know if it helps

23rd November 2020, 06:21 PM	#14
vincegironda diyAudio Member Join Date: Sep 2013	Heating and cooling made no difference

23rd November 2020, 11:10 PM	#17
vincegironda diyAudio Member Join Date: Sep 2013	Correct, I have clean signal in one channel only Can I pick up the signal from IC 764 and inject into the other ic's? If yes do I pic up the 764 input signal or output signal?

23rd November 2020, 11:15 PM	#19
vincegironda diyAudio Member Join Date: Sep 2013	OK will give it a go, thank you

24th November 2020, 10:07 AM	#20
vincegironda diyAudio Member Join Date: Sep 2013	So Perry I did as you suggested and injected signal from 764 to the other 3 DACs and found 761 produced clean audio 762 produced clean audio 763 no audio and it muted the signal from 764. Looks like 762 is defective, shall I remove it from the circuit and see what happens?