One board closer to burn-in and that sweet music!
SX-1010 project
- Thread starter Motnick
- Start date
With issue #1 resolved I decided to move on to the control amp board today in an attempt to see if I could resolve issue #2.
I had another go with the tone control switch and all 4 pots with deoxit D5 and then I replaced all 8 transistors. I checked all of the take out transistors, but all 8 passed the 6-way test.
After cleaning the controls and replacing the transistors I powered the set back up on the dbt, but the issue remained. I still see a spike in the right channel offset and the set goes into protection for a couple of seconds anytime that the tone control switch is flipped.
I think I’ll go ahead and replace all of the capacitors to close out the work on the control amp board and see if issue #2 clears up. I may also give the other push button controls another round with deoxit D5 while I am at it. Hopefully this is as simple as a bad cap or a dirty switch?
I would love to resolve this issue before I move forward with the other boards.
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Those switches have always cleaned for me on SX-xxxx models including my 1010 but others here have problems that won't go away and disassemble to clean. I suppose it is also possible that yours is damaged internally?
I tried to disassemble and clean on my SX-950 because "I was in there anyway and wanted to do it right". Re-assembling these switches is tedious and getting the crimp just right was enough of a chore that I ordered a used board with switches from eBay and installed it in my 950, have only cleaned with D5 since.
I tried to disassemble and clean on my SX-950 because "I was in there anyway and wanted to do it right". Re-assembling these switches is tedious and getting the crimp just right was enough of a chore that I ordered a used board with switches from eBay and installed it in my 950, have only cleaned with D5 since.
I went ahead and completed the recap on the control amp board. I also spent a couple of hours going back over all of the switches and pots throughout the entire unit with deoxit. I let everything dry up over night and then powered the unit back up on the dbt tonight. Issue #2 is now gone. The unit stays out of protection, and the offset in both channnels stays near zero while flipping the tone control switch! The offset in general seems much more stable since completing this work.
I did notice that my control amp board has a couple of capacitors hanging off of the board near the wire wrap pins. You can see them in the picture below. I read an old thread on the forum last night that explained that these caps were used on some very early sx-1010’s, but that they are not listed in the service manual. The SN on my unit (UA3900529M) lists it as January 1974.
http://audiokarma.org/forums/index....nderway-need-help-please.203201/#post-2456683
I think I’ll go ahead and add a couple of caps to my next Mouser order to replace these. They are both 47uf/16v. I was thinking of using the same 667-EEU-FM1E470 part that I used for C49-C52 on the control amp board. Would this be an ok choice?
I did notice that my control amp board has a couple of capacitors hanging off of the board near the wire wrap pins. You can see them in the picture below. I read an old thread on the forum last night that explained that these caps were used on some very early sx-1010’s, but that they are not listed in the service manual. The SN on my unit (UA3900529M) lists it as January 1974.
http://audiokarma.org/forums/index....nderway-need-help-please.203201/#post-2456683
I think I’ll go ahead and add a couple of caps to my next Mouser order to replace these. They are both 47uf/16v. I was thinking of using the same 667-EEU-FM1E470 part that I used for C49-C52 on the control amp board. Would this be an ok choice?
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The 667-EEU-FM1E470 will be fine. Go ahead and use 'em.
I was able to finish up the second power amp board today. The left amp was much easier to do with the completed right amp to use as a guide. I also reinstalled the outputs using new micas and fresh thermal paste.
Even though the left channel seemed to be working fine before hand, Q11 (2sc945) failed the 6-way test in this channel as well. In the right channel Q11 (2sc945) had continuity in all 6 tests using the 6-way test method. In this channel Q11 only had continuity in 1 of the 6 tests. I was surprised to find that the same transistor had failed in both boards. Anything that I should be checking as a cause for this?
Both bias and offset are easily set now, and both seem rock solid.
Even though the left channel seemed to be working fine before hand, Q11 (2sc945) failed the 6-way test in this channel as well. In the right channel Q11 (2sc945) had continuity in all 6 tests using the 6-way test method. In this channel Q11 only had continuity in 1 of the 6 tests. I was surprised to find that the same transistor had failed in both boards. Anything that I should be checking as a cause for this?
Both bias and offset are easily set now, and both seem rock solid.
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I’m starting to see the light at the end of the tunnel with this project. Lately I have been working on replacing the indicator bulbs with LEDs. I had several burnt out and I figured the LEDs would be a nice upgrade. It took me awhile to find a good technique for replacing them, and I thought I would share my experiences with it here.
I found that pulling them through the front is the easiest method. I cut the old bulb off once it’s pulled through, and I leave the leads as long as possible. Only the bulb gets removed.
Then I pull the leads back through to the inside. On some of them I was able reroute the wires to be able to pull more through to the front side. I strip the wires back and tin the tips. I also add heat shrink tube and push it down the wires.
I didn’t notice it on the first bulb that I removed, but the old bulbs have a little gray plastic label that gets left in the hole for the bulb when you remove it. The LEDs that I purchased won’t fit back in the hole with that label still inside. I fish them out with a pick tool.
I cut the leads down on the LED and stagger the cuts so that the heat shrinked joints can pull back through the hole one before the other. I don’t think that both solder joints will pull through the hole if they’re side by side.
I soldered the shortest lead first then slide the heat shrink through to the front. Once that’s done I did the same thing to the second lead.
Next I pushed the bulb back into the hole. The LEDs that I have fit snugly back in the hole without any fuss.
Last step is to verify that the new LED is working using the dim bulb tester. It’s slow and tedious, but it should be worth all of the effort once it’s done.
I found that pulling them through the front is the easiest method. I cut the old bulb off once it’s pulled through, and I leave the leads as long as possible. Only the bulb gets removed.
Then I pull the leads back through to the inside. On some of them I was able reroute the wires to be able to pull more through to the front side. I strip the wires back and tin the tips. I also add heat shrink tube and push it down the wires.
I didn’t notice it on the first bulb that I removed, but the old bulbs have a little gray plastic label that gets left in the hole for the bulb when you remove it. The LEDs that I purchased won’t fit back in the hole with that label still inside. I fish them out with a pick tool.
I cut the leads down on the LED and stagger the cuts so that the heat shrinked joints can pull back through the hole one before the other. I don’t think that both solder joints will pull through the hole if they’re side by side.
I soldered the shortest lead first then slide the heat shrink through to the front. Once that’s done I did the same thing to the second lead.
Next I pushed the bulb back into the hole. The LEDs that I have fit snugly back in the hole without any fuss.
Last step is to verify that the new LED is working using the dim bulb tester. It’s slow and tedious, but it should be worth all of the effort once it’s done.
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I was able to complete the phono board today.
I also replaced the main filter caps and bleeder resistors.
I went back to the power supply board and replaced the three metal oxide resistors. The originals still measured fine, but I wanted to lift them up off of the PCB board to help prevent any more scorching.
I also replaced the main filter caps and bleeder resistors.
I went back to the power supply board and replaced the three metal oxide resistors. The originals still measured fine, but I wanted to lift them up off of the PCB board to help prevent any more scorching.
Now that everything has been replaced I dialed in the bias and offset on full power. No more dbt! Everything seems to be working good now and the unit sounds very nice.
I also checked my power supply voltages. Some of them are a little off from the manual. I’m not sure if they are close enough, or if maybe I need to dig a little deeper? It seems like the negative voltages aren't low enough, and that the positive voltages are a bit too high.
Pin 8 - (13.4) 13
Pin 9 - (-13.0) -11
Pin 10 - (-56.0) -53.6
Pin11 - (-24.0) -21.6
Pin 13 - (35.0) 36
Pin 14 - (56.0) 57.8
Pin 15 - (24.0) 27.6
It would be great to get some advice from all of you on these voltages, as I am not sure if this is an issue or just normal variance.
I also checked my power supply voltages. Some of them are a little off from the manual. I’m not sure if they are close enough, or if maybe I need to dig a little deeper? It seems like the negative voltages aren't low enough, and that the positive voltages are a bit too high.
Pin 8 - (13.4) 13
Pin 9 - (-13.0) -11
Pin 10 - (-56.0) -53.6
Pin11 - (-24.0) -21.6
Pin 13 - (35.0) 36
Pin 14 - (56.0) 57.8
Pin 15 - (24.0) 27.6
It would be great to get some advice from all of you on these voltages, as I am not sure if this is an issue or just normal variance.
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Nicely done!
Voltages are fine.
I have the minity'est minty 1010 I've ever seen and I though about using Dowojo's LED's for the function indicators. Wasn't sure how they would fit. Used them in other units. Thanks for posting the images and results.
Voltages are fine.
I have the minity'est minty 1010 I've ever seen and I though about using Dowojo's LED's for the function indicators. Wasn't sure how they would fit. Used them in other units. Thanks for posting the images and results.
We don't start worrying about regulated power supply voltages if they are at or within 10 percent of target, and we temper that even, by looking first at the variation from ideal of the controlling zener diode's voltage. If that's off, everything else will be off.
I see nothing to be concerned about in your posted readings.
Congratulations, and it looks great!
I see nothing to be concerned about in your posted readings.
Congratulations, and it looks great!
I'm not much of an LED conversion fan, and in the 1010 I almost always leave the lights dimmed, which will not work properly with LEDs (think it looks great in a dim room with the lights dim).
Beautiful work!! Looks great.
You know, your right. I've been a big fan of OEM but the lighting circuit on the 1010's is the weakest, cheesiest circuit in a otherwise beautiful receiver. The dimming feature is poorly engineered. LED's help limit the current through the inadequate switches, but then you loose the dimming function.
A conundrum. I really don't like that word
Poorly designed? You might be right, but mine worked fine so I didn't complain. To satisfy my curiosity though, what is the weak point of the design?
I didn’t realize that I was going to lose the dimming feature by adding the LEDs when I decided to order them as replacements. All I knew was that most of the bulbs were burnt out in my 1010, and that replacing with LEDs might help to lighten the load on the dimmer switch. Once completed I realized that the dimmer feature isn’t as dramatic as it was with the incandescent bulbs. It does still work, just not to the same degree.
Maybe a compromise of LED in the indicators and incandescent in the dial/meter lamps would work better? Swapping the dial/meter bulbs isn’t too much of a headache. I think I’ll just enjoy it as is for now and see if the dimming thing bugs me.
I plan to enjoy the SX-1010 while I repair the SX-950 and 9090db that I’ve picked up these past few months. This has become a fun hobby for me. Thanks to everyone on this forum for all of the support!
Maybe a compromise of LED in the indicators and incandescent in the dial/meter lamps would work better? Swapping the dial/meter bulbs isn’t too much of a headache. I think I’ll just enjoy it as is for now and see if the dimming thing bugs me.
I plan to enjoy the SX-1010 while I repair the SX-950 and 9090db that I’ve picked up these past few months. This has become a fun hobby for me. Thanks to everyone on this forum for all of the support!
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Thanks mark. I really appreciate the help and advice of forum members like you. This simply would not be possible for guys like me without the help and support that people like you provide. If I ever get the chance, the first beer is on me.
