Marantz 4060 Problem

[BobC63]

Amplifier troubleshooting questions:

I friend saw that I was able to repair my QX-949 and has asked me to take a look at his Marantz 4060 Quad Amp because it has a couple of issues.

First I cleaned it out and applied Deoxit and Fader Lube to all the pots / sliders / buttons as it had been sitting idle for a long time. I also replaced the indicator lamp as it was burnt out.

Here are the 2 issues I see:

#1 - under normal operating conditions, the sound is distorted (see demo videos). The distortion appears on each of the 4 channels; both the main and remote speaker terminals; and also out of the headphone jacks. Choice of signal input (tuner / phono / tape / aux) does not change symptoms. Seems a little worse at higher volumes. Interesting that when turning the power button off the volume level increases and distortion disappears for the few seconds before the unit loses all power, also upon startup it is clear (and a bit louder) for the first 2-3 seconds; then the volume level fades a bit and the distortion starts. I even figured out a way to cycle the power button every 3 seconds or so and then the distortion disappears completely. Not sure if this is a ‘clue’ to the source of the problem, or just a coincidence.

Does this sound like a power switch problem? I did hit it with Deoxit once; I could try a second cleaning if anyone thinks that would help.
If it’s not the power switch; where should I look next?

#1 - the left side channel, volume is extremely low no matter what I do. It IS producing sound, but barely audible... and raising the volume does nothing.

We would love to save this amp; but my friend said he doesn’t want to have to spend $500 to save it.

Suggestions???

 

[Soundfield]

Have you measured what the power supply rails are doing?

 

[ar surround]

It seems as if the unit is going into some sort of protection mode after a few seconds. But I couldn't tell you how to mess with a feature like that.

 

[Doug G.]

It's a power supply problem and the distortion disappears after turnoff because voltage from the transformer is being removed and so, only DC is getting to the circuitry., The power supply needs to be troubleshot. It's a good chance the big filter and/or other caps are bad.

The low volume on the left channels need to wait until the primary problem with the PS is fixed.

Doug

 

[timbre4]

I have a 4140 amp myself; bought for $250 and had to spend $500 to get it singing like it is now. 45 year old caps and such aging components simply had to be replaced. Did the LED update too. Keeping the tone controls on flat because those are still bad and very hard to find!

Good luck with power supply troubleshooting.

 

[Quadwreck]

My 4060 served me faithfully until a few years ago, when I noticed the audio getting distorted. Now it sits in my pile of "someday to be fixed" gear.

 

[MidiMagic]

The low volume could be caused by a shorted component that is also pulling down the power supply.