Thanks for your reply. I thought that I might have given the impression that I was throwing the towel in, but that is not the case. I did scope the area where I measured the resistors and simply got the same readout as previously and I thought that perhaps I was doing it incorrectly. Scope set to 0.5s and 2v.
As long as you are interpreting the readings correctly then the scope is confirming that the lack of bass is present coming out of the DAC... which is truly weird and bizarre to me.
That frequency sweep starts at 10 Hz and although that frequency is very low the scope should show the trace moving up and down to the same amplitude (top to bottom points) on the scope screen as it does at the higher frequencies.
Please forgive all of you my intrusion and if I, without having any technical expertise in the field of electronics, allow myself to write in a thread where high expert people in terms of experience and knowledge really help to solve problems on a daily basis, but sometimes I like to follow the evolution of a thread that at least here practically always translates into being able to find the solution.
What if it was the tantalum capacitor that failed?
Just recently I had read something about the fact that especially those manufactured many years ago almost always fail now.
In all likelihood I could be wrong, and I apologize again for having intervened in this thread without having any technical expertise, but I thought that trying costs (almost) nothing at this point. 🙂
The big big problem we have in all this is not just identifying what is actually happening and which is why the measurements are key to seeing what is really going on but also the fact that the DAC board and opamp filters in all the diagrams are just for one channel, and the fault on this player seems to be on both channels.
If the measurements prove the bass fault is on both boards then I really don't where to go next tbh. Are we looking at an 'analogue' issue that is affecting both channels... could a bizarre ground issue affect and cause cancellation at LF... that seems very unlikely.
Is the DAC correctly outputting the data fed to it and has the incoming data been stripped of the low frequencies. I can't imagine any chip fault that could do that so perfectly, yes it can be done in the digital domain by deliberate manipulation of data (digital filtering or 'tone controls' operating in the digital domain) but this is a basic CD player. So it is all super puzzling at this stage.
The two DAC/filter boards.
If the measurements prove the bass fault is on both boards then I really don't where to go next tbh. Are we looking at an 'analogue' issue that is affecting both channels... could a bizarre ground issue affect and cause cancellation at LF... that seems very unlikely.
Is the DAC correctly outputting the data fed to it and has the incoming data been stripped of the low frequencies. I can't imagine any chip fault that could do that so perfectly, yes it can be done in the digital domain by deliberate manipulation of data (digital filtering or 'tone controls' operating in the digital domain) but this is a basic CD player. So it is all super puzzling at this stage.
The two DAC/filter boards.
I have been having a good look around (perhaps I should have done this before) (see pics) Both XLR's soldering does not look like stock and appears to have been re-soldered/ messed with. There are solder blobs on the Grd tags on each XLR which has had a wire attached to each but had been cut off. There is a cap that is wobbly in the bank of caps pictured (the bottom one with the hot melt blob) all the others are tight to the board. I have scoped again and inserted an XLR lead in each socket and jiggled it around as there was a suggestion that there could be a grounding problem but this did not
change the scope pattern. The hot melt does not look factory.
change the scope pattern.
change the scope pattern. The hot melt does not look factory.
That soldering does look a bit scrappy for sure.
Tell what, make sure all components are back soldered up normally and then desolder the 6 wires from the board that go to the sockets. Desolder them at the socket end.
You have pictures so you know where they all go as it is now. Leave the wires floating and not shorted to anything and then measure with the scope again using the black wire as the ground to the scope and THEN see what is on the red and blue wires for each channel.
Is the bass still missing or not?
Tell what, make sure all components are back soldered up normally and then desolder the 6 wires from the board that go to the sockets. Desolder them at the socket end.
You have pictures so you know where they all go as it is now. Leave the wires floating and not shorted to anything and then measure with the scope again using the black wire as the ground to the scope and THEN see what is on the red and blue wires for each channel.
Is the bass still missing or not?
I once made a mistake in cable placement on a pair of balanced XLRs.
To my surprise, even when connected incorrectly, it still sounds, but lacks bass.
@Puffin
From what I see in the picture above, both the wiring with the two XLR connectors are wrong.
The red should go in the center, and instead the blue has been soldered in both ones, that is, the wrong wire on the center pin.
You could use the following picture I found out there as a reference.
To my surprise, even when connected incorrectly, it still sounds, but lacks bass.
@Puffin
From what I see in the picture above, both the wiring with the two XLR connectors are wrong.
The red should go in the center, and instead the blue has been soldered in both ones, that is, the wrong wire on the center pin.
You could use the following picture I found out there as a reference.
I am just about to go out but I have just removed the board which has made it easier to see what is what. I should say that in htese matters you should never assume anything. I see that on the L channel where the wires XLR/RCA wires enter the board that + has the blue wire there. I checked for continuity on the XLRs and RCAs and they all seem to be linked/connected in some way as the DMM is beeping wherever I probe between the legs of the XLRs or RCAs which is clearly not right. I will look for replies when I retun.
Direct continuity (0.00 ohms, a short circuit) will be because of the shorting action of the muting relay. That is how it works, shunting all the output pins to ground when power is off.
Oh, I thought I had been lucky! Seems the - wire in the + is not right though. Will investigate.
An XLR balanced output wired out of phase can sound like lack of bass in some systems.
The wiring Logon has astutely noticed is the same as the separate picture posted #45, (also from the net) they both look like stock machines.
Just to complicate matters further, by standards they are both colour coded wrong!
Standard XLR wring:
Pin 1 0V Gnd usually screen/ green (in this machine it's Black.)
Pin 2 + Hot (in phase) usually red
Pin 3 - Cold (inverted phase) usually blue ( the upper middle pin on your machine)
...but that doesn't mean anything if the PCB end of the wiring is also different, best to check from source:
Puffin, on your machine; according to the Left PCB wired connection pic you've managed to upload, and the standards of XLR wiring, and the way it is wired on the output XLR's, it appears to be correct!
Another diversion!
Eliminate those relays as a possible fault.
Unless ive missed it, we are yet to know whether or not the signal is the same on the digital AND both analogue outputs.
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@Earths
With all due respect and sincere respect, I would simply solder the reds to the center pin and try to listen since it is possible that the designers simply did not care about the standard color code for XLR wiring.
Besides, when I assemble XLR cables I mainly pay attention to the correct relative position of the colors, but not to the standard of the colors (if any), but it's just my view.
Just as an example, Neutrik seems to suggest other colors as standard.
Furthermore, I guess that the above cannot in any way harm the piece.
With all due respect and sincere respect, I would simply solder the reds to the center pin and try to listen since it is possible that the designers simply did not care about the standard color code for XLR wiring.
Besides, when I assemble XLR cables I mainly pay attention to the correct relative position of the colors, but not to the standard of the colors (if any), but it's just my view.
Just as an example, Neutrik seems to suggest other colors as standard.
Furthermore, I guess that the above cannot in any way harm the piece.
I meant: "Compared to what are presumably the original boards (in fact I had also compared them with the picture in post #45).
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I disconnected the leads from the XLRs and scoped but the trace remains the same. From what I have seen the rear of a male XLR is Pin1 Grd, Pin 2 Pos and Pin 3 Neg. I checked the soldering of the wobbly cap and it is fine.
I'm running out of ideas with this one at this point tbh.
Are you able to record the audio output of the player directly onto your PC. Is that something you have ever done before, feeding the outputs into a PC or laptop? Its just a thought, no worries if not.
Are you able to record the audio output of the player directly onto your PC. Is that something you have ever done before, feeding the outputs into a PC or laptop? Its just a thought, no worries if not.
Logon, certainly not disagreeing with you, quite the contrary. It's the difference of perspective that can help problem solve, looking at another way.
Puffin, post 68 is the way for you to locate such oddities, it has to be worked through...
There is no easy route in fault finding, patience and persistence buddy!
The process of elimination is the procedure, then to a multi-meter, same applies.
Its a great feeling when you discover and resolve the fault!
Puffin, post 68 is the way for you to locate such oddities, it has to be worked through...
There is no easy route in fault finding, patience and persistence buddy!
The process of elimination is the procedure, then to a multi-meter, same applies.
Its a great feeling when you discover and resolve the fault!
I can only completely agree. 👍
At this point I wouldn't have been able to wait even a moment and I would have soldered the red wires to the central pin and then I couldn't wait to hear the result.
In the worst case scenario, it would have taken me less than 5 minutes to get a further certainty.
But that's just me.
Nor ever me with you, at all. 🙂
I don't think I can record the audio direct from player to laptop without additional add-ons. It is said that some smart phones can record 30Hz to 30kHz although some will only go to 22kHz which is not the range that is important. Do you think a video of the sweep being played over my system with the CD6 and the same with another CD player be of anyy help? I have a cheapie analogue to digital converter with an RCA out but no USB.