Pioneer SX-1010 - One channel low (even with Pre Out)

[camgilbert]

Hi all,

I received a Pioneer SX-1010 with a number of issues.

The core issue though is that one channel is very low but this is intermittent.

90% of the time, its low!

I have Deoxed all switches and controls and even changed out the volume pot with no change.

I have also tested as unit as preamp only and the issue persists.

Prior to rebuilding each board, has anyone seen this issue with these units?

Many thanks in advance.

 

[john stumpf]

is this in all modes? fm am phono and aux?

 

[zebulon1]

Nothing commonly problematic. Good old fashioned troubleshooting is needed.
I would concentrate again on the switches. If in all input modes, switches after - well like the filters, mono and loudness.
The 1010 switches can be removed dissembled and thoroughly cleaned.
Maybe try these techniques:
When the decreased signal is present, start messing with the switches I mentioned.
Trace the bad channel at points between the boards or switches to narrow the issue.
Running the set balanced to that bad side and tap, push the boards with a wooden rod such as a chop stick when the issue occurs. Check near the wire wrap connections. Check the wire wraps visually and also by pulling on the wires to make sure they are connected.
The signal wires are easy to identify. They are twin lead shielded normally pink and white wires with a gray insulation cover.

 

[camgilbert]

Yep happens all inputs. I had done as you said above but sadly could not increase or decrease the issue. All pots and switches were thoroughly cleaned. (almost cost me a can of dexoit :/)

Im wondering about tr's and caps on the eq-amp board?

Also power supply? could that impact low level signals in preamp?

 

[larryderouin]

Transistors to REPLACE NO MATTER WHAT! IN THIS ORDER. 2sc1451 with KSC3503 on the amp boards. When this one goes, it takes most everything on the amp board.
The the TWINS 2sa725 and 2sa726. They go noisy or they break down and go soft (like your problem). Replace everyone on every board that has them with KSA992's.

This should help alleviate most problems unless you have a cap that puked all over the board. Once you have the problem children taken care on each board, test it after each board.

There are other's but these are the BIG 3.

The power supply if not working up to spec will have an effect on the operation of the whole unit. Best to shotgun the power supply board as they take a lot of abuse, overheating from location and lack of airflow. I'd do that one 1st as that's the Heart of the whole thing.

 

[camgilbert]

Thanks, I'm on it, will keep you informed!