• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Pioneer SX-1010 Weird Intermittent Protection Issue

Ben Rothman

Ben Rothman

Active Member
Hi,

I have been chasing an issue on my Pioneer SX-1010 for about a year. I have posted about it a couple of times; now and then, it will randomly jump into protect mode for 2 seconds and jump out. I have observed this issue for a year and can confidently say there is no pattern. It might not happen for two days or two months, and then it will randomly do it, and I CANNOT do anything to replicate the problem. It doesn't matter what input I'm on or how loud I play music. The 1010 has had extensive work done to it. So far, all the caps on every board have been replaced, some with WIMA film caps and the rest with nichicon gold. I also replaced the big filter caps. I replaced all the transistors on the tone/eq board, phono board, and protect board. I only replaced some of the transistors on the power amp boards, which I believe are the heavy hitters known to go bad. Regarding the power supply, I replaced all the capacitors, three transistors, and one resistor.



The transistors I haven't replaced are a couple on the AMP boards. Two or so on the board itself, and then the two transistors on the little heatsink on the amp boards are original.

The power supply had all new caps and three tiny black transistors on the board replaced. The transistors on the L-Shaped heatsink are original.

I'm unsure what's causing this issue, and it's frustrating. At this point, I think I should use the shotgun approach and replace all the remaining transistors. I'm happy to take photos of each board and upload them so you can see what parts are original. Who knows, maybe one of the known transistors was missed. I don't get why it's so intermittent, and I cannot for the life of me replicate the problem.

As a side note, I am running the 1010 with 4ohm speakers, but I don't think that's the problem. It never gets hot, even after hours of use. Just slightly warm.
 
Register to hide this ad
Small Update: I did realize that the bias is set to 50mv for both channels. Not sure if that would cause my issue, but I want to give all the facts.
 
Oerets said:
Search is down but IIRC there is a mention of the 50mv being to high. Thinking it was 25mv.

Will do a search again and see if I can find it.


https://www.audiokarma.org/forums/index.php?threads/sx-1010-bias-current-too-high.460892/

Post seven.
Click to expand...

Thanks for the reply! I’ve seen that mentioned once or twice. Would the bias being set to 50mv be causing this weird issue? I just don’t understand how I can’t replicate the problem. Like I mentioned in the original post, it might happen once every two days or once every 2 to 3 months.
 
I once had a SX939 that would do what it sound like your SX1010 is doing. The bias was up on it to around 60mv on both channels and I lowered it to 25mv and it stopped.

Did clean the trim pots before adjusting IIRC.
 
Oerets said:
I once had a SX939 that would do what it sound like your SX1010 is doing. The bias was up on it to around 60mv on both channels and I lowered it to 25mv and it stopped.

Did clean the trim pots before adjusting IIRC.
Click to expand...

Very interesting your SX-939 had the same problem. Would yours work fine for days, if not months then randomly click in and out of protection. After it does this once it continues to play fine fine. I cannot get it to replicate the issue.
The trim pots are all new new. Do you mind walking me through the steps to adjust the bias? I am familiar with inside of this machine and I'm relatively decent with my hands, but my tech was the one who did this work. I have also attached some photos of the top side of the unit. Maybe someone can tell if a known culprit was missed.IMG_3541.jpegIMG_3540.jpegIMG_3542.jpegIMG_3543.jpegIMG_3544.jpeg
 
Contact your tech that worked on the unit. They may more familiar with your equipment service history. I thought you had done all of the work on it.

The bias adjustment have been changed on yours. I do know there is a lot of care needs to be undertaken to prevent damage to outputs. So this is one I would not want to learn on.
 
If you have access to an oscope, I would look at the output signal, to see if the DC balance is drifting or jumping at times, on one or both channels.
The amp board uses 2SA 725's or 2SA726's at the input on the board (Differential section). Those transistors can cause popping, or drifting/jumping dc lever on the output. Jumping above design threshold can cause intermittant protect. A scope can show the jumping/drifting. A dc multimeter can show it as well, but easier to see on a scope.
 
Intermittent problems are the hardest thing to figure out. Sometimes you have to coax them into revealing themselves. Tapping the board with a non conductive probe is good for revealing bad connections. The other 2 methods I've used are to use freeze spray and heat to torment various components into failure. You can't fix it if you can't find it. Best of luck.

Oh, by the way, don't rule out new parts as not being the source of the problem. I've had many new parts that were faulty right out of the box.
 
You must log in or register to reply here.
Back
Top Bottom