Post by serafis on Jan 24, 2022 3:59:35 GMT -5
I have an Onkyo TX-NR414 that appears completely dead (no display, no LEDs, no buttons work).
The SMPS is working and standby power to the HDMI board is fine (+12V and +9V). The outputs from the regulators in the POWER SUPPLY section of the attached schematic (highlighted in yellow) are correct at 1.8V, 3.3V and 5.2V respectively. The main power relay is fine too.
However, the 3.3V regulator that supplies power to the MPU (Q702 in the attached schematic in the POWER SUPPLY(STBY) section, highlighted in red) is showing only around 0.8V on its output pin (input pin is 5V), and the resistance between its Output pin and Gnd pins is less than 2.5 ohms which seems far too low. I temporarily removed that regulator, but the resistance between its output and Gnd pads remains the same the same, so I suspect the problem is elsewhere.
Also, but not necessarily related or an issue, the +12V pins on JL801B and P802 read only around 5.5V, although the cathode side of Schottky D8962 (12V STBY, highlighted in green) reads 12V. I'm not sure what the purpose of this diode is. And D182 (highlighted in blue) gets quite warm.
From the schematic, I've measured those components I can in situ but haven't found anything obvious. I'm beginning to suspect a faulty MPU, in which case repair would be way beyond my skills, but I don't want to junk the receiver unless I have to!
So I'd really welcome any advice as to how to diagnose the issues further and whether they are fixable.
Thanks, Jon.
The SMPS is working and standby power to the HDMI board is fine (+12V and +9V). The outputs from the regulators in the POWER SUPPLY section of the attached schematic (highlighted in yellow) are correct at 1.8V, 3.3V and 5.2V respectively. The main power relay is fine too.
However, the 3.3V regulator that supplies power to the MPU (Q702 in the attached schematic in the POWER SUPPLY(STBY) section, highlighted in red) is showing only around 0.8V on its output pin (input pin is 5V), and the resistance between its Output pin and Gnd pins is less than 2.5 ohms which seems far too low. I temporarily removed that regulator, but the resistance between its output and Gnd pads remains the same the same, so I suspect the problem is elsewhere.
Also, but not necessarily related or an issue, the +12V pins on JL801B and P802 read only around 5.5V, although the cathode side of Schottky D8962 (12V STBY, highlighted in green) reads 12V. I'm not sure what the purpose of this diode is. And D182 (highlighted in blue) gets quite warm.
From the schematic, I've measured those components I can in situ but haven't found anything obvious. I'm beginning to suspect a faulty MPU, in which case repair would be way beyond my skills, but I don't want to junk the receiver unless I have to!
So I'd really welcome any advice as to how to diagnose the issues further and whether they are fixable.
Thanks, Jon.
