Pioneer GM-X862

warpedhifi · 2nd March 2011, 05:37 AM

I was given this amp to fix, and this amp has a strange problem ( I never seen before). This amp cycles power on/off very fast. The power light is constantly flashing. I checked all the fet's and outputs and everything checks out. I checked the 494 and none of the pins are reading above 5.6 volts, and all the pins are varying voltage power. The amp is getting 13.8 volts.

Any idea's???

Perry Babin · 2nd March 2011, 06:17 AM

Does it do it if you pull the rectifiers?

warpedhifi · 2nd March 2011, 03:18 PM

No, with D907 and D910 out, the amp powers up fine.

Perry Babin · 2nd March 2011, 08:09 PM

Reinstall the rectifiers, clamp all semis to the heatsink and power up the amp. Measure the DC voltage across each of the emitter resistors. Do any read greater than 0.000v DC when the amp is trying to power up?

Email me if you don't have the schematic diagram and want it.
babin_perry@yahoo.com

warpedhifi · 7th March 2011, 01:09 AM

Finally got back to this amp, and no, there is no DC voltage across any of the emitter resistors.

Perry Babin · 7th March 2011, 02:31 AM

Are the rectifiers shorted?

Are the secondary filter caps shorted?

warpedhifi · 7th March 2011, 06:01 PM

the rectifiers are good and so are the secondary caps.

Perry Babin · 7th March 2011, 09:43 PM

When you say that the amp powers up fine with the rectifiers out of the circuit, do you mean that the power supply drains have a clean square wave swinging from ground to about 24v?

warpedhifi · 7th March 2011, 11:04 PM

I checked it again, with the oscope, and with the rectifiers out of the amp. I get around 0 to 7 volts, on the PS drains.

What I was seeing before, was the power light staying on and not flickering like when the rectifiers are in. Sorry about that.

Perry Babin · 7th March 2011, 11:14 PM

Set the cal knob fully clockwise.

Is the gates or the drains? It looks like the gates.

2nd March 2011, 05:37 AM	#1
warpedhifi diyAudio Member Join Date: Jul 2006 Location: Denton, Tx	Pioneer GM-X862 I was given this amp to fix, and this amp has a strange problem ( I never seen before). This amp cycles power on/off very fast. The power light is constantly flashing. I checked all the fet's and outputs and everything checks out. I checked the 494 and none of the pins are reading above 5.6 volts, and all the pins are varying voltage power. The amp is getting 13.8 volts. Any idea's???

2nd March 2011, 06:17 AM	#2
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Does it do it if you pull the rectifiers? __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

2nd March 2011, 08:09 PM	#4
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Reinstall the rectifiers, clamp all semis to the heatsink and power up the amp. Measure the DC voltage across each of the emitter resistors. Do any read greater than 0.000v DC when the amp is trying to power up? Email me if you don't have the schematic diagram and want it. 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

7th March 2011, 02:31 AM	#6
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Are the rectifiers shorted? Are the secondary filter caps shorted? __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

7th March 2011, 09:43 PM	#8
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	When you say that the amp powers up fine with the rectifiers out of the circuit, do you mean that the power supply drains have a clean square wave swinging from ground to about 24v? __________________ 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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2nd March 2011, 03:18 PM	#3
warpedhifi diyAudio Member Join Date: Jul 2006 Location: Denton, Tx	No, with D907 and D910 out, the amp powers up fine.

7th March 2011, 01:09 AM	#5
warpedhifi diyAudio Member Join Date: Jul 2006 Location: Denton, Tx	Finally got back to this amp, and no, there is no DC voltage across any of the emitter resistors.

7th March 2011, 06:01 PM	#7
warpedhifi diyAudio Member Join Date: Jul 2006 Location: Denton, Tx	the rectifiers are good and so are the secondary caps.

7th March 2011, 11:04 PM	#9
warpedhifi diyAudio Member Join Date: Jul 2006 Location: Denton, Tx	I checked it again, with the oscope, and with the rectifiers out of the amp. I get around 0 to 7 volts, on the PS drains. What I was seeing before, was the power light staying on and not flickering like when the rectifiers are in. Sorry about that.

7th March 2011, 11:14 PM	#10
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Set the cal knob fully clockwise. Is the gates or the drains? It looks like 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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