• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Marantz 4240 Quad , left channel problem

T

tiimm

Member
Hi,

I picked up a 4240 Quad yesterday and started looking why it didn't gave me any sound..

Found 2 fuses that were blown (on the plate that has 4 fuses), and replaced them..

Cleaned the switches / knobs..

Now i have a problem :

Right channel plays very well, no cracking at all!
Left channel : when powering unit on, makes cracking/humming sound, and the sound is very distorted! When turning the volume knob it makes a cracking sound, sometimes it sounds reasonally, but then a second later it goes back to nothing..

Cleaned the power mode switch also..


Thx!
 
Register to hide this ad
I bet you have blown out transistors in the amp channel . I would check them and also check the caps in the amp and pre amp board too . But you can have a number of things going on under the hood of the reciever . If you can fix I would do it , but if you cant Ibet it wont cost that much for a pro to fix it for you .
 
Yeah, its very strange..

5 minutes ago, everything was playing good (even the left channel)

Now, left & right channel are acting weird..

How can i check the transistors / caps?

I have experience in soldering so thats no problem :)
 
^+1 get yourself a can of deoxit d5 and drown those controls before you do anything else. If you have a meter and feel comfortable using it checking the bias and offset of the amp would be the next step.
 
Check you caps Im betting you have a weak cap in the power amp board . Its losing charge thats why its cutting out . I sean this before .
 
esr meter for checking the caps or pull them out and use your multimeter set to cap check . .Look on youtube on how to check a transistor .
 
Never, ever cycle the rear panel 'Power Mode' switch with the unit turned on.
The rear panel 'Local/Remote' switches on these usually need cleaning and must be in the local position if you don't have the optional wired remote plugged in.
I would set the power mode switch to the 17W x 4 position to do all testing.

Tom
 
Yup, I'm with Tom. Never try and troubleshoot a quad in bridged mode, it will make it confusing as all hell. Set it to 17wx4, find the source channel and pull/test the outputs.
 
I borrowed a multimeter from a friend of mine, i can now measure Ohm (or isnt that the thing i have to measure from the capacitors?)
 
I read about a trick with the multimeter, if you set it to Ohm and the cap gives out 0 it's shorted..

Do i have to disconnect every single cap? or can i measure them while they are on the board?

thx
 
set your meter on DC mv . turn vol down on amp .set to aux .put meter leads one on black the other on red speaker terminals .do this for left and right channels. report your finding
 
Left channel (front) gives me 9 - 10 (on 200mv setting)
Right gives me 3v

Left channel (rear) gives me 9
Right channel : 3v


This without any input on the aux
 
You must log in or register to reply here.
Back
Top Bottom