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Pioneer VSX-D503S Pro-Logic Receiver (Distortion)

 
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slydog



Joined: 28 Nov 2010
Posts: 3

PostPosted: Sun Nov 28, 2010 6:43 pm    Post subject: Pioneer VSX-D503S Pro-Logic Receiver (Distortion) Reply with quote

I have this Pioneer VSX-D503S Pro Logic Receiver that came in with the typical intermittent audio cutting in and out with static due to the overheated solder connections on the amplifier board.

I got the amplifier board rebuilt and everything works great except I noticed when doing final test of the unit in any "surround sound" mode the "right" front channel has severe distortion but only the right front channel, the left, rear, and center channels are clear as a bell.

If "surround" mode is off the right channel sounds great. I have checked for solder bridges on the DSP pro logic board, and tested input and output caps, along with even tapping the signal straight from the output of the DSP board "L OUT" and "R OUT" and all sounds great in stereo or surround mode.

I realize I must be missing something here and have never ran into this problem before with only one of the front channels having such severe distortion but only when surround mode is on, almost like a bad cap or op amp.

Any help or tips where to check next would be appreciated, as would the schematic as I am working without one currently to save costs on the repair.

Thanks, Slydogsrus
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torbjorn



Joined: 07 Jun 2007
Posts: 370
Location: Sweden

PostPosted: Mon Nov 29, 2010 8:24 am    Post subject: Reply with quote

If you supply a sine signal from a tone generator to the amplifier and study the output with an oscilloscope, can you see which kind of distortion it is (symmetrical or asymmetrical clipping, crossover distortion, superimposed high frequency oscillations etc)?
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slydog



Joined: 28 Nov 2010
Posts: 3

PostPosted: Tue Nov 30, 2010 1:24 am    Post subject: Reply with quote

Actually I did just that today, applied a 1khz sine wave with tone generator and determined the fault is in the DSP Pro Logic board.

The level on the "right" channel drops by 50% and starts clipping with surround mode on and the " left" channel changes amplitude some with surround on but has no clipping at all. Both the "right" and "left" channels sound great and have equal amplitude when bypassing the DSP board and just running stereo mode.

Now I really need a schematic for the Pioneer VSX-D503S as I am unable to even find a pinout for the Sanyo LA2785 IC that controls surround modes. Board number is ANP1763-B,which also seems to be a rare part number.

Thanks, Slydog
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voivoda



Joined: 23 Jun 2004
Posts: 63

PostPosted: Wed Mar 23, 2011 7:16 am    Post subject: Reply with quote

for pinout try http://image.pinout.net/ .... write some request around your image and wait for help Smile
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