Marantz SR5012 Blown Channel

[mmartell]

Left front channel blown both Darlingtons shorted C-E. Emitter resistors R467 and R468 open as well as base resistor R458.

Is there anything else that might be suspect judging by the failed components ? I can look at the schematic but my inability to "read" it and see what's really happening leaves me at a disadvantage.

Is it advisable to use the Dim Bulb tester on an amp driven by a microprocessor like these are or that doesn't matter ?

[redwire]

Re: Marantz SR5012 Blown Channel

R468, R467 are the Front Right channel.

When audio power amp output transistors short, the previous (driver stage) is usually also dead or damaged. You must parts check upstream.

If the 22R fusible resistors are blown, then an overload went back to previous stages. Bias transistor Q421, Q414, Q424 could also get overloaded, and need to be checked. If Q421 is open-circuit, then C423 would pop.

I just check every transistor with a multimeter on diode-test, it takes a couple minutes. Comparison readings to other (working) channels can also help.

[mmartell]

Re: Marantz SR5012 Blown Channel

Yes you are correct it was the right front channel that was blown. Base resistor R483 for the other darlington was out of spec as well. I borrowed parts from one of the surround back channels to repair the right front channel.

Upon testing the Left Front channel is lower in volume than the other channels. Worse yet there is no HDMI output to the tv.

I have no history on this unit it was in ASO Protection when I received it.

[redwire]

Re: Marantz SR5012 Blown Channel

I guess you'd have to see if the power amp channel is quiet, although rare because you usually get distortion if a part is not working. Other Marantz models people are replacing the volume control IC. Have to inject a sine-wave and measure ACV to know for sure.

Reset to Factory Settings:
Turn off the power using Power Button.
Press Power Button while simultaneously pressing M-DAX and ZONE2 SOURCE.
Remove your fingers from the two buttons when “Initialized” appears on the display.

[mmartell]

Re: Marantz SR5012 Blown Channel

I've reset it - no changes. The lowered volume on that channel I will investigate later...

I've discovered that I get video output for a short time after a cold power-on. The Analog Devices video processor seems to heat up over a minute or two and the pic goes out. Could just be a coincidence though as video processors generally run hot.

[mmartell]

Re: Marantz SR5012 Blown Channel

With someone else's troubleshooting help I ran a jumper and HDMI is functioning again. It is not the proper solution but that requires HDMI board removal and due to issues with another similar Marantz I have and the way they're put together I'm content at the moment to leave well enough alone.

But there is another problem with this not connecting to LAN but working over wifi. Starting another thread for that.