Post by serafis on Sept 10, 2022 0:23:27 GMT -5
This is the VSX-920K I got working back in Fed 22, thanks to help from this forum, details in my earlier post. The amp has been working fine since then.
I've never used headphones on this amp until today. When I did, they worked for about 5 minutes, then the amp powered off in DC Protect mode. After releasing it from Protect Mode, now, if anything is inserted into the headphone socket enough to trigger the detection circuit (even a plastic tube or Q-tip), the amp immediately goes to DC Protect. Apart from this, the amp still works fine. While I seldom use headphones, it would be nice to find a solution to this.
The service manual for the VSX-920K is completely wrong, as noted in other posts (e.g. the HDMI board is shown down the side when it's actually across the top). The service manual for the VSX-1020K seems to be more accurate for this amp, and can be found here at manualslib. I've followed the schematics as far as I'm able, but I don't really know what I should be looking for as DC Protect never triggers when used normally with speakers.
Supply voltages measure within reasonable limits. I've measured XHPDET (HP detect) on the 'scope as normally high at 3.3V where it enters the Digital Main Assembly, dropping to zero as soon as something is inserted into the headphone socket. I assume what should happen then is that the microprocessor detects this and turns off all the speaker relays and turns on the headphone relay. But instead, it immediately goes to DC Protect. When running normally with no inputs, the speaker terminals measure around -25 to -65mV DC.
Not sure what else to check so any help greatly appreciated.
I've never used headphones on this amp until today. When I did, they worked for about 5 minutes, then the amp powered off in DC Protect mode. After releasing it from Protect Mode, now, if anything is inserted into the headphone socket enough to trigger the detection circuit (even a plastic tube or Q-tip), the amp immediately goes to DC Protect. Apart from this, the amp still works fine. While I seldom use headphones, it would be nice to find a solution to this.
The service manual for the VSX-920K is completely wrong, as noted in other posts (e.g. the HDMI board is shown down the side when it's actually across the top). The service manual for the VSX-1020K seems to be more accurate for this amp, and can be found here at manualslib. I've followed the schematics as far as I'm able, but I don't really know what I should be looking for as DC Protect never triggers when used normally with speakers.
Supply voltages measure within reasonable limits. I've measured XHPDET (HP detect) on the 'scope as normally high at 3.3V where it enters the Digital Main Assembly, dropping to zero as soon as something is inserted into the headphone socket. I assume what should happen then is that the microprocessor detects this and turns off all the speaker relays and turns on the headphone relay. But instead, it immediately goes to DC Protect. When running normally with no inputs, the speaker terminals measure around -25 to -65mV DC.
Not sure what else to check so any help greatly appreciated.
