I had one of these come in for service recently due to a complaint that one of the channels would drop out. Typical situation of dirty pots/switches/etc. Actually, ended up being a bad speaker protection relay. I was also asked to go through the unit and make sure all was well. In testing this guy I found some issues that appears to be a common problem with this model....
1. FM Stereo will not work. When disengaging Mute/Stereo, it works fine in mono, but you get nothing when in 'stereo mode'
2. FM tuning meter (three LED's) does not work either. The left most LED (red) stays light no matter where you are at on the dial, even when you have a strong signal on the strength meter.
3. FM and/or AM output is noticeably low compared to aux and phono inputs.
4. Upon initial power up, the unit comes out of protection mode as expected, but Speaker Protection LED 1 stays lite. (Not really concerned about this right now.)
All of the above i have found in articles on AK as well as the web with absolutely no resolution to any of it. I wont tell you how much time I have spent on this tuner board, but i am finding things that absolutely make no sense to me and the service manual is absolute garbage....and is actually wrong/missing parts that are installed. There is no tuning procedures at all for the amp or tuner. In any case, what i am finding is very concerning to me. I think this unit is filled with a bunch of fusistors. These are yellow and pink looking resistors in various values. I have removed each of them....and every last one measures as an open circuit. I have been replacing them with like value standard carbon resistors but nothing i do seems to help....in fact, in some locations, putting in a properly working resistor creates a hum and actually makes the tuner work worse. Now the strange part. Every last 'fusistor' i am taking out, according to the screen printing on the board, should be a capacitor. I have looked at the schematic (for whatever that is worth), and do actually find in the parts list that the capacitor number that the fusistor was installed in is actually identified in the parts list as a real capacitor. I fully expect that these resistors were intentionally installed, but honestly, the schematic and parts list do not agree. In addition, there are a large number of parts that are installed that do not show up in the parts list and i cannot find them in the schematic....particularly, some diodes in key areas of the FM muting circuit. This obviously is a problem because i cannot identify what model the part is as some of these do not look the same and I am not going to guess at any of this. I am about to raise the white flag on this as i am not able to do anything to fix this FM issue. I have gone through and pulled every signal part to very it is working. I have even replaced the IC chips with known good working units. Still nothing.
I realize that this is a model made when Marantz was owned by Philips and from what i gather, the build quality took a nose dive during this era. I could really use some kind soul out there who had tackled this beast to help me figure out what is going on here. Again, what i am experiencing seems to be common to this model....so I am hoping someone can point me in the right direction.
1. FM Stereo will not work. When disengaging Mute/Stereo, it works fine in mono, but you get nothing when in 'stereo mode'
2. FM tuning meter (three LED's) does not work either. The left most LED (red) stays light no matter where you are at on the dial, even when you have a strong signal on the strength meter.
3. FM and/or AM output is noticeably low compared to aux and phono inputs.
4. Upon initial power up, the unit comes out of protection mode as expected, but Speaker Protection LED 1 stays lite. (Not really concerned about this right now.)
All of the above i have found in articles on AK as well as the web with absolutely no resolution to any of it. I wont tell you how much time I have spent on this tuner board, but i am finding things that absolutely make no sense to me and the service manual is absolute garbage....and is actually wrong/missing parts that are installed. There is no tuning procedures at all for the amp or tuner. In any case, what i am finding is very concerning to me. I think this unit is filled with a bunch of fusistors. These are yellow and pink looking resistors in various values. I have removed each of them....and every last one measures as an open circuit. I have been replacing them with like value standard carbon resistors but nothing i do seems to help....in fact, in some locations, putting in a properly working resistor creates a hum and actually makes the tuner work worse. Now the strange part. Every last 'fusistor' i am taking out, according to the screen printing on the board, should be a capacitor. I have looked at the schematic (for whatever that is worth), and do actually find in the parts list that the capacitor number that the fusistor was installed in is actually identified in the parts list as a real capacitor. I fully expect that these resistors were intentionally installed, but honestly, the schematic and parts list do not agree. In addition, there are a large number of parts that are installed that do not show up in the parts list and i cannot find them in the schematic....particularly, some diodes in key areas of the FM muting circuit. This obviously is a problem because i cannot identify what model the part is as some of these do not look the same and I am not going to guess at any of this. I am about to raise the white flag on this as i am not able to do anything to fix this FM issue. I have gone through and pulled every signal part to very it is working. I have even replaced the IC chips with known good working units. Still nothing.
I realize that this is a model made when Marantz was owned by Philips and from what i gather, the build quality took a nose dive during this era. I could really use some kind soul out there who had tackled this beast to help me figure out what is going on here. Again, what i am experiencing seems to be common to this model....so I am hoping someone can point me in the right direction.