You have to know how a circuit works before you can trace a signal through it and be confident that what you hear with an audio probe or see on an oscilloscope is what you are looking for and at the correct level. I've watched people screw this up and get frustrated trying to trace signals in circuits they simply don't understand and never needed to before. If you are new to electronics and discrete audio circuits in particular, it's not a simple task to trace the insides of a preamp/DAC, no matter how many hours you spend staring at a PCB which probably contains several functional blocks and mysterious LSI chips with no obvious indication what or where their functional circuits start and finish.
Most anyone can recognize shapes and colours of physical elements like Lego blocks or resistors but the invisible currents that flow and their logical operation and sequence in discrete circuits, is another thing entirely. A schematic or at the very least, a functional block diagram, is an aid that's necessary to be certain of what you are looking at. Without it, even experienced techs will be flying blind.
A bad connection or solder joint will often respond to physical shock like tapping on a PCB (not with a hammer though!) or even blowing hot air over both sides to provoke the effect of broken joints or traces. At least you can do that much in the hope that the fault is just this simple. I'd be looking at electrolytic capacitor types too - some SMD types are just trash.
Most anyone can recognize shapes and colours of physical elements like Lego blocks or resistors but the invisible currents that flow and their logical operation and sequence in discrete circuits, is another thing entirely. A schematic or at the very least, a functional block diagram, is an aid that's necessary to be certain of what you are looking at. Without it, even experienced techs will be flying blind.
A bad connection or solder joint will often respond to physical shock like tapping on a PCB (not with a hammer though!) or even blowing hot air over both sides to provoke the effect of broken joints or traces. At least you can do that much in the hope that the fault is just this simple. I'd be looking at electrolytic capacitor types too - some SMD types are just trash.
I second that, not for the inexperienced.
And some of these use very bad quality RoHS solder, another problem area.
And some of these use very bad quality RoHS solder, another problem area.
I looked at a picture of the PCB and there appears to be a relay between the line output stage and the RCA jacks.
If you are getting a normal output voltage with no load, I doubt that any active components are bad.
Perhaps it really is best to leave it to a professional repair tech since that PCB is also carrying mains voltage.
In general, I would agree with you.
In this case, I would suspect a passive component or contact problem very close to (circuit-wise) the output RCA jacks.
Normally this kind of problem is easy to diagnose because of the symmetry between the 2 channels (i.e. the good channel can be used as a reference).
It's usually not so difficult to trace the circuit backwards from the RCA jacks through a few passive components.
If we were talking of old style DACs, Id also agree that someone who knew what problems to look for in a commercial product or followed a forum thread like this one where actual repair techs and experienced DIYs may be discussing how they go about repairs, compare notes with others and guide a group of followers who probably have similar problems. However, I haven't seen a recent model DAC where the PCB(s) weren't virtually 100% SMT and it's just not realistic to expect that an average DIY will be confident enough to work with those very small format semis, regardless of the amount of work aids, specialist soldering gear gear and data they collect and practice with, in preparation.
I agree.
I was thinking something like a (hopefully) a simple diagnosis like finding a significant voltage drop across the relay contacts, and finding a replacement part.
If not comfortable with replacing the part, find someone who can.
Otherwise, the repair options may be more limited.
Just had a similar problem on setup.
Turned out to be intermittent break in RCA cable.
The cable had been under my chair and I must have rolled wheels over it and damaged it.
