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Another Pioneer SX-1010 Fix-Me-Up

T

TimmahTao

AK Member
I'll preface this by admitting that I am a newbee at electronics work, but I have loved vintage audio for a long time; I grew up listening to vinyl with the Marantz 7/8/10 set up that my grandfather bought new and that my father recovered and restored. I dig the sound of this era, compared to the clinical accuracy of some newer equipment.

Looking to upgrade my own set up with something within my budget, I bought a Pioneer SX-1010 with a wonderfully restored cabinet. Sounded good when I auditioned it at the guys home. Got it home, sounds great.

For a couple days.

Then I started to notice a few symptoms, that progressed rapidly.

1.) On every input EXCEPT for the Auxiliary, there is a faint 'put-put-put-put-put' sound. Whisper the words as fast as you can and you'll get the idea. This noise increases as you turn up the volume. This is consistent and hasn't gotten better or worse.

2.) Snaps, Crackles, and Pops. I noticed a bit of snapping on the treble, so I cleaned off the connectors, and switched speaker terminals. That seemed to improve the situation temporarily, but they have gotten much worse. Now, when speakers are plugged in and the amp is on, I'll hear some fuzz, and then WHAMMO, full volume pop and crackle noises. This is independent of volume and happens regardless of which input is used
​
Here is what I have done:

1.) Cleaned the terminals and connectors.

2.) Cracked open the case to look for loose connections. Found that the disc capacitor on the power switch was detached on one side, so I resoldered it. I did not see any other loose connectors, other than a ground binding post on the bottom that has the remains of solder, but no wire attached to it. I have noticed that even when I have the chassis grounded, I hear some attenuation on FM when I touch the front panel. Could there be a short?

3.) Rebalanced the power supplies. Hold at 0mV and 50mV on both sides.​
The receiver has been repaired before, the previous tech left a few insulated wire leads hanging where he connected and disconnected individual boards. Not very neat, but I didn't see any loose, uninsulated wires. Some of the capacitors have been replaced, but the main power caps look like the giant black originals. These repairs were done recently enough that they include the suggested inclusion of the flyback diode across the terminals.

For the record, I have no idea what a flyback diode does, but I have read all the other SX1010 threads and know that it is a recommended addition by MarkTheFixer, and others. This should give you an idea about my electronics knowledge and abilities.

So what should I look for and do now?

If this is beyond my abilities as a electronics novice, does anyone here live in NYC and want to troubleshoot with me? Homebrewed beer, mead, and food will be provided. If not, can anyone recommend a decent tech to pay to fix it in Brooklyn or Queens?
 
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Does the put-put sound come from both channels?

You can separate the pre-amp from the main amp buy removing the jumpers from the back of the set. Now the 1010 can be operated as a per-amp or just a power amp. Try using it as both with another set to isolate the issue. See what I mean?

Also: At the pre-in, main out: you can use an RCA cord and swap the pre-amp to the other side main (channel), if the put-put is only on one side (channel). Switch the sides and see if it follows.

The hum thing when touching the faceplate might be harder to isolate but try reversing the wall plug (unplug the set and turn the plug 180 degrees and plug it back in the the wall outlet). See what happens.

I just re-read the post and saw the put-put was non-existent in aux. Makes a difference. Sorry. A good cleaning is in order. Deoxit the controls every one of them.
 
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You need to read all the posts about setting the idle current. There is an error in the manual. It should be set at 25mv per side. MTF will/may chime in on the put-put issue. Clean all the pots and switches that go up and down and round and round with deoxit and then fsderlube on the pots. Build a dim bulb tester as you will need it. Get the service manual from hifiengine, free only have to register. Read the manual to understand the layout and the terms.
 
Zebulon, the put-put seems to be coming from both channels, and unfortunately, I don't have another set easily accessible to test out the preamp or amp separately.

I just got an order of DeOxit with wee little brushes. I'll give it another shot.

Craxx, I haven't seen the 25mv per side error before. Can you point me at the right posts? Would that really cause the kind of problem I am having?
 
TimmahTao said:
Zebulon, the put-put seems to be coming from both channels, and unfortunately, I don't have another set easily accessible to test out the preamp or amp separately.

I just got an order of DeOxit with wee little brushes. I'll give it another shot.

Craxx, I haven't seen the 25mv per side error before. Can you point me at the right posts? Would that really cause the kind of problem I am having?
Click to expand...

The put-put issue is not from the bias current setting I just wanted you to know about the issue. The dim bulb tester will be needed later after you start replacing transistors and pots. Use the search function for the 25mv issue. It will help you find other posts about recsps of that unit.
 
TimmahTao said:
I'll preface this by admitting that I am a newbee at electronics work, but I have loved vintage audio for a long time; I grew up listening to vinyl with the Marantz 7/8/10 set up that my grandfather bought new and that my father recovered and restored. I dig the sound of this era, compared to the clinical accuracy of some newer equipment.

Looking to upgrade my own set up with something within my budget, I bought a Pioneer SX-1010 with a wonderfully restored cabinet. Sounded good when I auditioned it at the guys home. Got it home, sounds great.

For a couple days.

Then I started to notice a few symptoms, that progressed rapidly.

1.) On every input EXCEPT for the Auxiliary, there is a faint 'put-put-put-put-put' sound. Whisper the words as fast as you can and you'll get the idea. This noise increases as you turn up the volume. This is consistent and hasn't gotten better or worse.

2.) Snaps, Crackles, and Pops. I noticed a bit of snapping on the treble, so I cleaned off the connectors, and switched speaker terminals. That seemed to improve the situation temporarily, but they have gotten much worse. Now, when speakers are plugged in and the amp is on, I'll hear some fuzz, and then WHAMMO, full volume pop and crackle noises. This is independent of volume and happens regardless of which input is used
​
Here is what I have done:

1.) Cleaned the terminals and connectors.

2.) Cracked open the case to look for loose connections. Found that the disc capacitor on the power switch was detached on one side, so I resoldered it. I did not see any other loose connectors, other than a ground binding post on the bottom that has the remains of solder, but no wire attached to it. I have noticed that even when I have the chassis grounded, I hear some attenuation on FM when I touch the front panel. Could there be a short?

3.) Rebalanced the power supplies. Hold at 0mV and 50mV on both sides.​
The receiver has been repaired before, the previous tech left a few insulated wire leads hanging where he connected and disconnected individual boards. Not very neat, but I didn't see any loose, uninsulated wires. Some of the capacitors have been replaced, but the main power caps look like the giant black originals. These repairs were done recently enough that they include the suggested inclusion of the flyback diode across the terminals.

For the record, I have no idea what a flyback diode does, but I have read all the other SX1010 threads and know that it is a recommended addition by MarkTheFixer, and others. This should give you an idea about my electronics knowledge and abilities.

So what should I look for and do now?

If this is beyond my abilities as a electronics novice, does anyone here live in NYC and want to troubleshoot with me? Homebrewed beer, mead, and food will be provided. If not, can anyone recommend a decent tech to pay to fix it in Brooklyn or Queens?
Click to expand...

Before you get too deep replacing parts and spraying chemicals, It would be wise to access the operation of the main amp and pre amp separately.
Pull the main in and pre out jumpers. Then drive the main amp with an external preamp source, how does it work? Then connect the pre out jacks to an external main amp source.
Do you hear any of the issues you seem to be having connected this way? Doing this will help you isolate which section (maybe both) are causing an issue.
 
craxx6969 said:
The put-put issue is not from the bias current setting I just wanted you to know about the issue. The dim bulb tester will be needed later after you start replacing transistors and pots. Use the search function for the 25mv issue. It will help you find other posts about recsps of that unit.
Click to expand...

Found some of those in the stickied recap lists. I'm not actually worried about the put put sound, its pretty mild and doesn't interfere when music is playing. Its really only the extremely loud static and POPs that are bothering me, and like I said, they seem to be full volume, regardless of the volume set.

I'm a little worried about my speakers! Won't this damage them? But without them, how can I hear whether I have had an effect?

Anyways, another question. Looking for broken things, I noticed that the ground wire terminal on the bottom is not attached to anything. It looks like a crooked finger sticking above and parallel to the steel grate that is under the bottom plate of the receiver. It has the 'grounding' signal right next to it. It has the remains of some solder, but I don't see any loose wires.

What SHOULD it be attached to, if anything. I imagine that could cause some issues. When it was plugged in, I had it grounded either through the phono ground connector, or the antenna ground connector. Is there a better way?
 
glen65 said:
Before you get too deep replacing parts and spraying chemicals, It would be wise to access the operation of the main amp and pre amp separately.
Pull the main in and pre out jumpers. Then drive the main amp with an external preamp source, how does it work? Then connect the pre out jacks to an external main amp source.
Do you hear any of the issues you seem to be having connected this way?
Click to expand...

As I mentioned before, I don't think I have another discrete amp. Know anyone in Brooklyn who wants to come over and help me out? Or another way to test the preamp solo?
 
TimmahTao said:
As I mentioned before, I don't think I have another discrete amp. Know anyone in Brooklyn who wants to come over and help me out? Or another way to test the preamp solo?
Click to expand...

OK, when you said it was another Fix-me-up, you struck me as someone who might have a collection of various equipment.
 
glen65 said:
OK, when you said it was another Fix-me-up, you struck me as someone who might have a collection of various equipment.
Click to expand...

If you don't feel comfortable working on it I would recommend not doing any probing into the unit with anything. Too easy to cause further damage. I don't know of anyone in your area to assist you. Wait and someone may help out.
--------------------
Found the article about the 50mv vs what it should be 25mv per side.

http://www.audiokarma.org/forums/archive/index.php/t-460892.html

You will need to scroll down towards the end of the page to see the results. It is supposed to be set at 25mv per side, not 50mv. I wonder if the SX-1050 has the same error as that is also set at 50mv per side. I will check to see if the heat goes down on the 1050 if I reduce the idle current to 25mv per side.

Both the 1010 and 1050 run hot so the reduction of the idle current will lower the heat output on those power supply heatsinks.

Thanks to Zebulon1 for the catch. Always great to have more info!
 
glen65 said:
OK, when you said it was another Fix-me-up, you struck me as someone who might have a collection of various equipment.
Click to expand...

Haha, there just seem to be a couple of threads about relative newbees getting SX-1010s and trying to fix them. This is another one!

Think that if I say "Mark the Fixer" three times fast, he will magically appear and make everything alright?
 
craxx6969 said:
If you don't feel comfortable working on it I would recommend not doing any probing into the unit with anything. Too easy to cause further damage. I don't know of anyone in your area to assist you. Wait and someone may help out.
--------------------
Found the article about the 50mv vs what it should be 25mv per side.

http://www.audiokarma.org/forums/archive/index.php/t-460892.html

You will need to scroll down towards the end of the page to see the results. It is supposed to be set at 25mv per side, not 50mv. I wonder if the SX-1050 has the same error as that is also set at 50mv per side. I will check to see if the heat goes down on the 1050 if I reduce the idle current to 25mv per side.

Both the 1010 and 1050 run hot so the reduction of the idle current will lower the heat output on those power supply heatsinks.

Thanks to Zebulon1 for the catch. Always great to have more info!
Click to expand...

*Chuckle* Not uncomfortable at all, you quoted the wrong guy. I'd love to help him out, but I'm in Ohio.
 
Getting a can of deoxit and soaking those controls and push buttons is step one. I worry that the popping is from the dreaded 2SA726 differential pair on the amp board. That board also has the notorious 2SC1451 which is best to sub out.

I'm jumping to conclusions without even seeing the unit obviously. The power supply should be addressed at some point along with the protection circuit. Can you replace parts or need to take it to a tech?
 
HVHiFI said:
Getting a can of deoxit and soaking those controls and push buttons is step one. I worry that the popping is from the dreaded 2SA726 differential pair on the amp board. That board also has the notorious 2SC1451 which is best to sub out.

I'm jumping to conclusions without even seeing the unit obviously. The power supply should be addressed at some point along with the protection circuit. Can you replace parts or need to take it to a tech?
Click to expand...

Is there an updated parts list? I see that some of the recommended parts at Mouser are unavailable, so any tips in terms of substitutions would be handy.

Correct me if I'm wrong, but it is better to just replace those transistors preemptively, wherever they are? Is it safe to assume that I should not turn on the amp until those get replaced?
 
I think the power amp part could be tested JUST by unplugging the pre-out jumpers and then, plug your speakers and listen.

I think for that '' put put '' sound, you do not need any audio input.

Sounds like some feedback-cycling-motorboating effect.

Again, if it's independant of inputs, volume control, tone controls, it appears

strongly to be in the power amp section.

Nasty. !

Even if you soaks the switches and controls, it won't go away.

Do you have a I-pod ? It could be use as a source signal to test the power amp section ( again, not to monitor the '' put, put '' )

BUT BE VERY CAREFUL with the volume control of the I-pod... 'cause this way, you are feeding directly into the power amp.

Bonne chance !
 
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I found something else. Take a look at the picture from rowingcoaches thread I attached. The wire leading from the ground terminal to the power rail? is missing on mine. Could this be the source of my problem?

What resistor needs to go in there?

What effect would this connection have, if it were removed? For that matter, WHY would anyone remove it?
 

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zebulon1 said:
Give a better description.
Board number and pin.
Click to expand...

It's right next to the Power Supply Assembly on the overall diagram in the service manual. It is too blurry to read the writing, and it doesn't appear on blown up diagrams. The symbol of what I THINK it is is a little door-like symbol on the white wire that leads directly to the plug.
 
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