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Marantz 2015 has a new Hummmm...

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palanterra

New Member
Long time reader, first post..Looking for some advice, a point in the right direction if you will...This afternoon I noticed my 2015 has developed a slight hum, left channel only...Level of the hum is constant, does not change regardless of volume, is present across all inputs, and present across both left speaker inputs...Fades away if bass is turned all the way up...Disconnected FM antenna, turntable, etc, hum was still present with just speakers connected...In addition, when powering up the unit there is now a slight surge audible through the speakers...Thanks in advance.
 
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I’m not an expert on these but have some experience on the 2015, first thoughts:

1. confirm all switches and potentiometers on front panel are cleaned properly.

Download the service manual from hifiengine.

2. If you have an oscilloscope you could check on the left input to amp board (P600) and compare to right input signal. If noise is NOT present there and they are equal waveform this could indicate problem is in the amp section. I have found C609/C610 47uf, 50v caps failed and cause similar issues. Also check output coupling caps C623/C624 (2200uf/35v). Even number components are Left side on P600 amp board according to schematic.

If the noise IS present at input to P600 the problem most likely is before that point, possibly in preamp/tone section P500 board or controls on front panel.

3. Confirm the Bias and DC alignment per manual instructions.

I believe the “surge” or pop on power up is normal on these due to no speaker protection relay and cap coupled design. Keep speaker select button off for several seconds for caps and DC voltage at output to stabilize. You can keep a 1/4” headphone adapter plugged into headphone jack that should help minimize this.

Others with more experience may chime in here. 2015 is nice sounding cap coupled receiver. Well worth the effort or expense to repair.
 
palanterra said:
Long time reader, first post..Looking for some advice, a point in the right direction if you will...This afternoon I noticed my 2015 has developed a slight hum, left channel only...Level of the hum is constant, does not change regardless of volume, is present across all inputs, and present across both left speaker inputs...Fades away if bass is turned all the way up...Disconnected FM antenna, turntable, etc, hum was still present with just speakers connected...In addition, when powering up the unit there is now a slight surge audible through the speakers...Thanks in advance.
Click to expand...

Slight surge is completely normal, never had a 2015 that didn't, has to do with it not having a time delay relay to keep the sound of the amplifiers energizing from Reaching the speakers.

Every single one I have seen has had completely failed caps in the amp board and a few in the PSU.

Keep in mind that these things are 40+ years old, and the life expectancy of a Capacitor, in an optimal environment is around 20.
 
Your 2015 has capacitive coupled outputs and no speaker relay, so you may hear the sound slowly fade out when you power it off. There may also be some 'pops' when the speaker and power switches are cycled.

Tom
 
Thanks for the replies...Great advice on start-up re the speakers and select button, and I do hear the 'pops' as noted above during switch cycling...Believe I have traced at least some of the issue to the power supply board as I can see at least two caps that look visibly bad...Might be time to go ahead and recap the entire receiver...
 
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