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Snap Crackle Pop 1050

DonHarper

DonHarper

Member
Greetings :) So I have Pioneer SX-1050 that suddenly started to "snap crackle and pop" one day last fall. I quickly turned it off, and decided this was going to be my spring project, and I put it in the closet. So here we are, late spring, it's back out of the closet. The sound is only on the left side (the other side plays normal). I turned it off, and pulled the "pre-out / power amp in" jumpers, turned it back on and it didn't make that sound. So I turned it back off, plugged the jumpers back in, turned it back on, and makes the same sound again. There also seems to be some other, not quite so loud noises coming from that side in between really loud ones. Any help would be appreciated.
 
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balance makes no difference?
volume up or down makes no difference?
muting (-20db) or loudness make no difference?
Tone on or off makes no difference?
High and low filters on and off make no difference?

Download the service manual for it.

The AWG-040 board (flat amp) has a pair of 2sa725 transistor troublemakers on it. Q7 & Q8.

open up the bonnet
pull off the bottom cover
pull off the faceplate

the volume control is mounted on a PC board that is part of a module, and right behind the volume control is our two troublemakers.

to pull that module that mounts all the controls, remove the 3 front panel screws that mount this module to the front sub panel
the module frame mounts the pots and switches which are soldered to the pc board in question: This shouldn't come apart.


once it is free of the sub chassis, the module can be pulled back a few inches on it's wires and tilted out of the cabinet.

Now you can see the culprits behind the volume control. 2sa725 transistors. infamous for doing this. get some ksa992 transistors.

the 2sa725 has a lead arrangement of BCE
the ksa992 .has a lead arrangement of ECB... OPPOSITE of the original.

desolder the bad, solder in the new paying close attention to which hole gets which wire from the component.

clean up the flux, clean up the board maybe recap it since the hard work is already done....

reverse the procedure to put it back together.

or

pay someone else big bux to do it for you.
 
Thanks for the quick response and info, gentleman. I have the service manual.
I'll try and have answers for your questions later on this morning, I know that Volume up or down, makes no difference. Not 100% sure on the rest, so I'll double check.
Best place for ordering ksa992 transistors? I'm sure I can probably Google it but I'd thought I'd ask. :)
Thanks for your time. :) I'll let you know.
 
balance makes no difference? No
volume up or down makes no difference? No
muting (-20db) or loudness make no difference? No
Tone on or off makes no difference? No
High and low filters on and off make no difference? No
 
Ok, so I purchased a Rebuild Kit AWG-040 & AWG-041 Recap & Repair Kit. It should be here in my hot little hands by the 16th of this month, and I'll let ya'll know. Thanks again everyone.
 
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