Marantz 4400 preamp problem.

[fmoyano]

hi there, im from south america (chile) and here is very difficult to obtain a "good condition" vintage marantz, in my country there is no more than 10 units in total!!. The problem (i suspect) is it at the preamp stage because i connected directly to the main in and all 4 channels woked fine. The problem is at the right-front channel, when i put it at louder volume the speaker becames to popping whith bass (more bass, more popping sound). also the oscilloscope in vari-matrix mode displayed the signal at only three corners (left-front and left,right-rear), so for that reason i think that the problem should be fron the pream section.

I also try with 4x50 and 2x125 mode and the same problem.
I think it is not on the front panel (balance, tape monitor) controls, because if you for example move the bass potentiometer the oscilloscope signal is the same, so the bad signal is before into passing for that controls.

From where do i start checking to fix that channel?, the preamp section is under the receiver?

Please help me, im not a tecnician, i need to fix this problem.




thanks a lot
Francisco.

 

[fmoyano]

HELP! Cannot turn off the oscilloscope.

hi there, im from south america (chile) and here is very difficult to obtain a "good condition" vintage marantz, in my country there is no more than 10 units in total!!. The problem (i suspect) is it at the preamp stage because i connected directly to the main in and all 4 channels woked fine. The problem is at the right-front channel, when i put it at louder volume the speaker becames to popping whith bass (more bass, more popping sound). also the oscilloscope in vari-matrix mode displayed the signal at only three corners (left-front and left,right-rear), so for that reason i think that the problem should be fron the pream section.

I also try with 4x50 and 2x125 mode and the same problem.
I think it is not on the front panel (balance, tape monitor) controls, because if you for example move the bass potentiometer the oscilloscope signal is the same, so the bad signal is before into passing for that controls.

From where do i start checking to fix that channel?, the preamp section is under the receiver?

Please help me, im not a tecnician, i need to fix this problem.




thanks a lot
Francisco.

I opened the unit from under the receiver and only I looked if there something wrong (something burned, etc), at my sight there still all fine, but when y put together to close the unit and i turned on, the oscilloscope IN THE OFF MODE displayed and started to automatically draw a line from up to center, and i cannot turn it off, If i turn on it displays the signal, but not centered, not very precised and also a small strange line diagonally. ¿What is happening?

please help me!!