Marantz 4240 left channel sounds fuzzy and muffled - video link in posting

[the retro la]

Hi Gang!


First time posting here, let me start by saying ahead of time that I respect and appreciate everyone's expertise here on AK.

I have a wonderful old Marantz 4240 that has served me well over the years. Recently a friend came over to listen to a mix of some recordings he recently made in a recording studio, which were a little heavy on the bass side of the frequency Spectrum. Not sure if that information is relevant or not, but I figured any info helps when trying to diagnose a problem. We had the audio source plugged into the Aux jack of the Marantz and all of a sudden after a relatively bass heavy portion of the song, the left channel became fuzzy and muffled sounding. Very similar sound to when the needle on a record player collects too much dust and dirt, and needs to be cleaned out. The volume was not abnormally loud.

Hooked up to the main speakers output, are Dynaco A25's. Hooked up to the remote speaker output are Optimus 7's. All speakers work fine, as tested by another receiver that I have.

The fuzzy output is on both the main and remote outputs. Issue seems to be isolated to the left channel, the right channel sounds just fine. It does not matter if the source is a.m. or FM radio, phono input, or auxiliary input.

I have filmed the issue, and uploaded it to YouTube. Here is a link illustrating the issue:

While I am by no means an electronics repair guy, I do have plenty of soldering experience, and have fixed guitar amps, and other electronics when I have been informed what the issue is, what to purchase and replace with. At minimum, with the help of the fine folks of AK, if we can at least isolate that it's a Transistor issue, and not a diode or capacitor issue for example, that will help significantly.


Thank you so much and I look forward to hearing from you!

 

[petehall347]

hard to say whats causing it .. might be a bad transistor or resistor . does that model have pre main rca sockets ? if so try playing something with a vol control into main in . like a phone or ipod

 

[the retro la]

hard to say whats causing it .. might be a bad transistor or resistor . does that model have pre main rca sockets ? if so try playing something with a vol control into main in . like a phone or ipod

Hi Pete,

Thanks for the reply, I took a look in the back and it does not appear to have the pre main RCA sockets. However, thought i would run a new discovery on the 4240, to see if this would make any additional sense to you? So the amp only makes the distortions on the left channel when it’s in 40 watt x 2 mode. If i power it off and switch it into 17 watt x 4 mode, it works fine. While it’s not as loud and full-sounding of course. I only had it on for 30 seconds to test it as such and turned it right back off. Does that make sense that it would behave that way, or is that equally as odd?

 

[petehall347]

try the other speaker outs .

 

[Tom B]

The problem could be components or as simple as a dirty speaker switch, or a dirty 2 ch/4ch switch. It also sounds like a speaker protect relay problem, but this unit doesn't seem to have one.

 

[catrafter]

The rear panel Local/Remote switch is frequently a problem on these. Clean it with DeOxit and cycle it many times, be sure to put it back in Local when you are done.

Never, ever cycle the rear panel 'Power Mode' switch with the unit turned on.

Tom