SX1010 Crackling on Aux

[TimmahTao]

Hi Folks. I have an SX1010 that was 'refurbished' by an unnamed member of the forums who offered such services in PMs when I posted about failing transistor issues when I first purchased it a few years back.

Long story short, it was a bad experience. It took them almost a year, they increased the cost by $100 over the agreed upon price after I drove to a different state to pick it up because "it took them so long" and was so hard, and when I eventually got it home one of the phono channels didn't work. They refused to fix it or offer a partial refund, so moved on with my life and hooked up a third party phono stage to the AUX input and have been using it that way for the last couple of years.

The Problem: In the last couple of weeks, I have been getting crackling and popping in the right channel when using the AUX input. If I raise the volume, the crackling causes protection circuit to cut out the channel, so I discontinued use of the input.

Testing: Switched the phono stage over to the other inputs (Tape 1/2, 4-Channel Adaptor, Dolby NR) and the problem goes away. AM/FM both come through loud and clear. Removed all inputs and plugged in a pair of headphones with nothing else hooked up. Clear on all inputs/switches except for AUX. Constant crackling in right channel when set to AUX.

Diagnosis: PreAmps/Amps working fine. Balance/Volume fine with no crackles on movement. EQ working fine with no crackling on adjustment.
AUX switch needs cleaning?

Treatment: Deoxit the hell out of it. Remove top and bottom case to access backs of switches. Deoxit into the back of AUX switch with front facing down for penetration. Waited a minute or two and cycled switch rapidly for 5 minutes. Waited 5 minutes and repeated. Did all the other switches and pots since I was in there. Waited 10 minutes, Deoxit Gold into back of all switches and cycled them to distribute cleaner.

Retesting: Still got crackling on the right channel when set to AUX with nothing hooked up.

So what do I do now?

 

[zebulon1]

Below is something to ponder as I sort out the issue:

Check the routing of the shielded wires from the AUX RCA jacks to the switch boards. You might have to remove the rear plate shield. Maybe a screw or metal chassis part has pinched the wire?

If the other sources are operating without the pops, it has to be within the AUX circuit to the switch(s). It's only a shielded lead.
The signals travel through all the input/function switches, not just the AUX switch.
I would remove the switch gang and dissemble each switch and clean it per MTF's process. Remember: The AUX and Phono 2 are switches that for the most part are never used. They are the focus.
While your in there, look for loose wires and wire-wrap pins. Re-flow all the connections regardless of any confirmed discrepancy's.
It's hard for me to admit a member here would do a poor job on your receiver but . If the guy was in a hurry, many proper restoration procedures could if of been missed.
Here's a thread I posted on the cleaning. I'll try to find the others regarding the cleaning.

 

[TimmahTao]

Below is something to ponder as I sort out the issue:

Check the routing of the shielded wires from the AUX RCA jacks to the switch boards. You might have to remove the rear plate shield. Maybe a screw or metal chassis part has pinched the wire?

If the other sources are operating without the pops, it has to be within the AUX circuit to the switch(s). It's only a shielded lead.
The signals travel through all the input/function switches, not just the AUX switch.
I would remove the switch gang and dissemble each switch and clean it per MTF's process. Remember: The AUX and Phono 2 are switches that for the most part are never used. They are the focus.
While your in there, look for loose wires and wire-wrap pins. Re-flow all the connections regardless of any confirmed discrepancy's.
It's hard for me to admit a member here would do a poor job on your receiver but . If the guy was in a hurry, many proper restoration procedures could if of been missed.
Here's a thread I posted on the cleaning. I'll try to find the others regarding the cleaning.

Thanks for the thoughts, Zebulon.

Time to bust out the dental picks and give those wires a tug, eh? I figured it has to be in that circuit somewhere. Might take me until next weekend to check that run though; it's hard to spread out an electronics project with a threenager in the house.

What is odd, is that if anything, the cleaning procedure made the problem WORSE. The crackling was intermittent before the heavy cleaning. Now it is steady low crackling. That might give credence to it being a pinched/rubbed wire. Taking off the case/moving it around may have worsened the loose connection?

Re: the restoration, I'm not sure how much of a hurry they could have been in, considering how long it took. They didn't even bother to refinish/polish up the wood, despite including it in the cost of the work. Case still has the walnut stain pen marks I delivered it to them with. Welp. Guess that's why I need to learn to do this stuff myself?

 

[zebulon1]

Pins 12 and 9 on the switch board (Board AWS-069) are from the AUX RCA jacks. You could desolder the pins and swap them. This would eliminate the receiver circuits. It might be a moot point but if your careful it would isolate the simple wire run to the back panel.
Of course, perform the visual check from the board to the back panel jacks first.
The rear shield is easy to remove. I remove it when working/removing the output heatsinks. Tip: Getting it out of the way, keeps it from being scratched or dented. You can access all the jacks from there.
I'm glad you decided to tackle this yourself.
Take your time.