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Pioneer SPEC-1/SPEC-4 Function Switch Noise

Any further suggestions anyone? I'd love to resolve this issue but could live with it if that's just the way it is.

I posted the voltages below early in this thread with values that seem to vary from the values on the schematics noted in red. I realize the variation is only .4 - .5 volts but that seems like a lot when the reference values are only .4 - 1 volt. Also, the voltages for Q1 through Q4 are very close to reference values then Q5 through Q10 have the variation. I don't have the circuit analysis skills to determine whether this is an issue or not. Nobody has commented on this so I'm wondering what the smarter folks have to say.

@calman46 , would you be able to check these voltages on your unit for comparison?

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Thanks,
Joe
 
With the main volume turn all way down there is no switching noise, so I don't think it's a problem with the circuit components. Take a look on page 33 of SM ( I have a hard copy) . You will notice the phono cables from the switch to the phono stage. The longer cable has only one end of the shield to the board, the shorter phono cable has both ends connected to the board. I assume the shield goes to ground but should you ground both sides of the shield ? I don't know.What was reason why it was done that way. What makes testing the Spec 1 tough is it does not have and independent headphone amp , it needs the power amp connected to it. I don't think routing the power amp back into the preamp is a good idea in this day and age . Pioneer made a C-77 preamp that looks just like the spec 1 but does not have the amp dependent headphone amp or the Speaker selector.
What do you think about adding a headphone amp inside the spec 1 ?
 
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I am getting some DCmV on the front wafer of the function switch and not on the rear wafer.You may want to look there. The relay is not clicking on this Spec 1 so "the game is afoot".
 
I don't know why the SM shows the difference in shield grounding between Phono 1 and Phono 2. Have you verified the actual wiring on the AWF-017?

I'm pretty sure I tested the noise without the amp rerouted back to the preamp and it didn't seem to make any difference.
 
Yes the actual wiring is like the SM. Rerouting the amp back into preamp wouldn't have anything to do with the phono switch noise, I was just complaining about it.
 
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Joe I just read your other thread on this and Mark had replied that the phono stage is always on . So that explains the switching noise, when changing phone inputs .
 
So, it appears this 'issue' isn't really a 'problem'. Rather, it's working as designed. I'm going to put it back together and enjoy it. The noise itself has never really been an issue for me since I always turn the volume down before changing sources (or speakers, for that matter). I only noticed it because I had a minor channel cutout and was going through all the controls to check for scratchiness. I cleaned and lubed all the controls which cleared up the channel cutout but not the phono noise.

Many thanks to all who have generously offered troubleshooting assistance. I will continue to watch this thread in case anyone comes up with something new.

Joe
 
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