Pioneer SX-1010 Right Channel Fade

[zyzzx78]

Hello,

I recently got a Pioneer SX-1010 that would produce no sound.

The foil between R21 and pin 13 on the power supply circuit assembly was broken or melted since pin 13 produced a 0 volt reading. The AWR-054 assembly looks like it has been overheated over the years.

By soldering a little jumper wire between R21 and pin 13, I was able to get the unit to play pretty well.

After a while the right channel faded out, powering off and on would help a little but eventually only the left channel would play.

I then went through the front panel controls with Radio Shack contact cleaner/lubricant which seemed to help, but only for a while.

Does anyone have any thoughts on how to correct this situation. :scratch2:

 

[markthefixer]

I then went through the front panel controls with Radio Shack contact cleaner/lubricant which seemed to help, but only for a while.

First clean ALL the switches with deoxit, and the controls with deoxit and faderlube. Contact cleaner doesn't cut it. This is LONG experience talking...

Also clean the pre-out / power amp in jumpers as well.

Since it isn't going into protection, the problem is still cleaning.

Deoxit is special - it loosens corrosion - and the mechanical motion of 50 full actuations scrubs it off.

Do more research here on deoxit - including where to get it and how to do it.

 

[zyzzx78]

OK, I will give it a try. Thanks for your help on this!

 

[jpdylon]

if you can ramp up the volume to make the channel come back - chances are the protection relay could be at fault too.

Loosen the screws that hold it to the chassis and pull it up abit. You can then go up from the bottom of the opening in the chassis with a small, then flat blade screwdriver pop the cover on each side of the relay and slide it off. Then using some 1000 grit sandpaper - carefully burnish the contact surfaces of the relay. You'll need to cut the sand paper into a small strip to get to the contacts mounted to the body. I will usually put the relay back together (minus the cover) and slide the paper in between the contacts, and press the contacts together to burnish the contact surfaces on the relay body.

Afterwords, just remember to leave the volume at minimum when powering up and down and you probably won't have the problem again.

Clear as mud?

 

[Thorerik]

Sometimes fade in amps is caused by thermal problems. Open circuit runs tell me that excessive current is flowing causing the melt. I suggest that you go to Radio Shack and get some component freeze spray. When the fade happens start with the output transistors. Spray a little freeze on them one at a time. Continue back through the circuitry spraying the components one at a time. Include capacitors, diodes, transistors, and resistors. When the sound comes back that's the component that may be at fault. I say may be at fault because the circuitry around a transistor may be causing the the bias to change cutting off or saturating the active component, the transistor. In this case you would go through all the trouble to replace the transistor and find that you still have the same problem. Caps are famous for this because with age they become leaky and loose their ability to block DC voltages which in turn changes the operating point bias of the transistors.

Cool thing about a stereo and some knowledge about electronics is you have a good channel to compare the signal path and biasing aginst the one in question. This is where a Oscilloscope comes in handy.

If you want to learn more about electronics and test equipment use Google to find the US Navy NEETS courses.

 

[BPRJam]

Did you ever figure this out? I just started rehabbing an sx-1010, and seem to have the same problem (minus the overheating and R21 component failure).

What component was causing the right channel to fade?