The other day, my Denon AVR-1801 home theater receiver stopped working. It would power on, reach the point where it normally enabled the speaker outputs, but then it would shut off. The status LED would rapidly blink on and off.
The user manual suggested that the device was overheating, or that the speaker terminals were being shorted. The device was not hot, as it was just turned on. I unplugged all input and output cables, but that didn’t fix it either. Time to dig deeper.
A quick Google search revealed the following gem. There are four “surge” resistors in line with the ±15 VDC regulators: R141, 142, 148, 149. These 1 Ohm resistors weaken over time with every power-on surge, and the resistors from the factory were not strong enough. Armed with this knowledge, I opened my receiver to test these resistors.
Without removing the board, you should be able to use a multimeter to measure the resistance of these resistors. According to the Internet, anything above 10 Ohms is considered bad. In my case, two resistors were completely open – infinity Ohms. Two others tested at around 2.8 Ohms.
To achieve a good quality repair, the board needs to be removed. My approach was to remove the back panel and take out only the affected board. In hindsight, I really should have simply removed both boards together, with the rear panel attached, from the chassis.
Once this board is removed, simply desolder the failed resistors and replace them with 1 Ohm, 1/2 Watt Metal-Film Flameproof resistors. From DigiKey these are $0.22 CAD each. At that price, I replaced all four at the same time.
There is the possibility that the failure of these resistors coincides with the failure of the next components in the circuit: the 7815 and 7915 regulators. To test these, with the multimeter in the diode test mode, check that none of the regulator pins are shorted together, as is the most common failure mode. This was not the case for me, though I ordered one of each regulator just in case.
The 7815 and 7915 regulators share the larger heatsink, while the 7805 is attached to the smaller single heatsink. If you’re lucky, these won’t need replacing, and simply changing the faulty resistors will bring your Denon receiver back to life!