A Harman/Kardon AVR 645 repair has been a hobby of mine for the past several years. My latest attempt involved the purchase of a DOA unit for part swapping and testing. The original AVR would power up then shut down after a few seconds. I completely tore down both units, found a couple of bad components and reassembled one of them. Same issue, no speakers connected. After extensive research I found a repair document from Harman/Kardon that explains the protection circuit in fantastic detail and provides specific test points for each fault (power, DC detection, overload & power) and the voltage values that tells me if there is a fault or not.
Long story short, it appears that the protection circuit is NOT responsible for the unit shutting itself down.
Any gurus here that could point me in a new direction of troubleshooting this kick-ass receiver?
I have 2 other Harman/Kardon receivers that are nearing 20 years of service (with some minor repairs). The only innovations of the last 20 years that these units lack is network/Bluetooth connectivity, Dolby Atmos, and HD/UHD. Don't care because these still sound terrific.
Any ideas would be greatly appreciated
It shuts off a couple seconds after turning on, but it isn't tripping any of the Protect circuits. Sometimes, not always, I can hear a slight buzz/sizzle right before it shuts down, but I can't locate the component that's doing the buzzing. It shuts down the moment any of the sources "lock in". Meaning the display stops showing everything and only shows the selected input and the inputs settings. I've created protect events by shorting speaker terminals and unplugging thermal sensors and it shuts down immediately.
Another observation. I can cycle through the sources for up to 10 seconds or so before it finally shuts off. What is being activated when this happens? Could it be an IC chip glitch?!
Replaced main large caps and most of the regulators. Tested dozens of caps and resistors.
I think this thing is mocking me.
Long story short, it appears that the protection circuit is NOT responsible for the unit shutting itself down.
Any gurus here that could point me in a new direction of troubleshooting this kick-ass receiver?
I have 2 other Harman/Kardon receivers that are nearing 20 years of service (with some minor repairs). The only innovations of the last 20 years that these units lack is network/Bluetooth connectivity, Dolby Atmos, and HD/UHD. Don't care because these still sound terrific.
Any ideas would be greatly appreciated
It shuts off a couple seconds after turning on, but it isn't tripping any of the Protect circuits. Sometimes, not always, I can hear a slight buzz/sizzle right before it shuts down, but I can't locate the component that's doing the buzzing. It shuts down the moment any of the sources "lock in". Meaning the display stops showing everything and only shows the selected input and the inputs settings. I've created protect events by shorting speaker terminals and unplugging thermal sensors and it shuts down immediately.
Another observation. I can cycle through the sources for up to 10 seconds or so before it finally shuts off. What is being activated when this happens? Could it be an IC chip glitch?!
Replaced main large caps and most of the regulators. Tested dozens of caps and resistors.
I think this thing is mocking me.
