Hello all,
I could use some help troubleshooting an issue with a Magnavox Concert Grand I'm in the process of getting up to speed. First, the issue:
Channel 1 works and I'm getting plenty of volume out of both the treble and bass amps of both amplifiers (each channel's amplifier is bi-amped). But there seems to be some problem with distortion/certain parts of the sound not coming through on channel 1. For instance, many songs have a clearly lower vocal (midrange?) presence. As a result, when I stand centered in front of the console it appears that more vocal and midrange sound is coming out of channel 2, though the overall volume out of each is about the same. On some music I hear some distortion on channel 1. Other recordings sound fine and balanced; I guess it's the recording mix.
I've eliminated a few things:
It is not a problem with either amplifier. The issue jumps from one set of speakers to the other when I reverse the RCAs out of the tuner/preamp chassis. And it's not any of the preamp tubes (three 12AX7s and one 12AU7) in the tuner/preamp section. I'm using known good tubes.
So, the problem has got to be something internal to the tuner/preamp chassis.
It's not isolated to the tape, phono or FM MPX stereo modes. It occurs regardless of the mode it's in.
Here is what I have done to the set:
All electrolytics, paper/wax caps and resistors 15 percent or more off spec have been replaced in both amplifiers, the tuner/preamp, the remote control receiver chassis and the tuner power supply chassis. I've cleaned all pots etc. All voltages are good in the amplifiers, but I haven't checked them in the tuner/preamp chassis. I also didn't touch any of the ceramic/disc capacitors in the tuner/preamp section.
Any ideas on where to look in the tuner/preamp? I have high res copies of the SAMs schematics if anyone would like me to send them.
The console is 85 percent there, but I would love to solve this issue and get it to 100 percent!
Thanks,
Ted
I could use some help troubleshooting an issue with a Magnavox Concert Grand I'm in the process of getting up to speed. First, the issue:
Channel 1 works and I'm getting plenty of volume out of both the treble and bass amps of both amplifiers (each channel's amplifier is bi-amped). But there seems to be some problem with distortion/certain parts of the sound not coming through on channel 1. For instance, many songs have a clearly lower vocal (midrange?) presence. As a result, when I stand centered in front of the console it appears that more vocal and midrange sound is coming out of channel 2, though the overall volume out of each is about the same. On some music I hear some distortion on channel 1. Other recordings sound fine and balanced; I guess it's the recording mix.
I've eliminated a few things:
It is not a problem with either amplifier. The issue jumps from one set of speakers to the other when I reverse the RCAs out of the tuner/preamp chassis. And it's not any of the preamp tubes (three 12AX7s and one 12AU7) in the tuner/preamp section. I'm using known good tubes.
So, the problem has got to be something internal to the tuner/preamp chassis.
It's not isolated to the tape, phono or FM MPX stereo modes. It occurs regardless of the mode it's in.
Here is what I have done to the set:
All electrolytics, paper/wax caps and resistors 15 percent or more off spec have been replaced in both amplifiers, the tuner/preamp, the remote control receiver chassis and the tuner power supply chassis. I've cleaned all pots etc. All voltages are good in the amplifiers, but I haven't checked them in the tuner/preamp chassis. I also didn't touch any of the ceramic/disc capacitors in the tuner/preamp section.
Any ideas on where to look in the tuner/preamp? I have high res copies of the SAMs schematics if anyone would like me to send them.
The console is 85 percent there, but I would love to solve this issue and get it to 100 percent!
Thanks,
Ted
