414 mkii channel 1 quiet compared to other channels

[topdrizzy]

So I thought it was the heads or pinch roller but I tried several decks and still have the same issue. all decks, pinch rollers have been cleaned and demagged as well. would it be something that would be on the top half of the machine or the bottom? I have fixed about a hundred 488 1 and 2 plus 424 1&3, 414 1&2 but im a noob when it comes to capacitors, resistors, transistors, Diodes etc.

 

[SkywaveTDR]

How is it possible to work on all that equipment and not know about these basic components?
The deck may have a gain stage issue. These units are for practice type use and not real world studio function. There are times I discover a dB or two off from other channels due to the grade of parts they used and that there are no line amp calibrations in them. one could go crazy and modify a op amp stage circuit to compensate or make up for a out of tolerance part but one would need to understand Op Amp gains stage equations and that is usually a stage or two above resistors, capacitors and diodes. It would benefit anyone working on these to have a study on DC and AC electronics even if on line as these all use that kind of stuff. Then Transistor amplifiers and then Operational Amplifiers are next. I studied all this stuff and build line amps in Radio when needed. It is not that hard. Use of a wireless breadboard is the way to gain experience with a signal source and scope.
The place where the problem is- can be found on the schematic and determining where the gain is different. Most the time the first op amp is damaged by phantom supplies or plugging guitar amps into these 1/4" connectors.