SX-980 Protection Overload Condition
- Thread starter danyost
- Start date
I'm going to be enjoying the best sounding receiver I've ever owned for as long as I can keep it running!
I've also got a CTF-1000 I'm going to fix the belts on. I do have some original recordings on cassette that I'd like to hear again providing that the tapes hold up. She's a beauty!
I've also got a CTF-1000 I'm going to fix the belts on. I do have some original recordings on cassette that I'd like to hear again providing that the tapes hold up. She's a beauty!
Spot on Zeb... 
I have LOTS of stuff waiting in the wings to sing again...
(one of them too)
I have LOTS of stuff waiting in the wings to sing again...
(one of them too)
That's an older post, it didn't specifically SAY awr-156 and when it gets QUOTED out of an old thread that provides the context it gets confusing.
So:
Replace
awr-156 Q3 2sa850
also because of potential overstress:
awr-156 q4 2sb682
awr-156 d9 mz-130
although considering the effort, a full rebuild of the board will not add much expense or effort, with an increase in reliability.
awr-156 q1 2sd712 100v 4a 30w 55-300hfe 8mhz
512-KSC2073TU npn to-220 bce 150v 1.5a 25w 4mhz 40-140hfe $0.54
awr-156 q4 2sb682 100v 4a 30w 55-300hfe 8mhz
512-KSA940TU pnp to-220 bce 150v 1.5a 25w 4mhz 40-140hfe $0.54
neither side is going to come close to an amp of current, no less 4 amps
awr-156 q2 2sc1735 100v 0.5a 0.8w 55-300hfe 130mhz
512-KSC2383YTA to-92L ecb 160v 1a .9w 50mhz 160-320hfe $0.17
awr-156 q3 2sa850 100v 0.5a 0.8w 55-300hfe 130mhz
512-KSA1013YBU to-92L ecb 160v 1a .9w 50mhz 160-320hfe $0.17 (R=60-120, O=100/200, Y=160/320)
awr-156 Q5 2sd712 512-KSC2073TU
awr-156 q6 2sc945a eCb 50v .15a .25w 300mhz 40-700hfe
512-KSC2383YTA to-92L ecb 160v 1a .9w 50mhz 160-320hfe $0.17
awr-156 d8 mz-140 512-1N5244B Fairchild 14 V, 0.5W Zener
awr-156 d9 mz-130 512-1N5243B Fairchild 13 V, 0.5W Zener
awr-156 d10 LZ230 512-1N4748A Fairchild 22 V, 1.0W Zener
awr-156 d11 LZ230 512-1N4748A Fairchild 22 V, 1.0W Zener
awr-156 c19,c20 4.7uf 50v 647-UPW2A4R7MDD 4.7uf 100v $0.14
awr-156 c17,c18 47uf 16v 647-UPW1V470MED 47uf 35v $0.16
awr-156 c24,c25 47uf 25v 647-UPW1V470MED 47uf 35v $0.16
awr-156 c11,c12,c15,c16 220uf 80v 647-UPM2A221MHD 220uf 100v $1.02 ea
awr-156 c13 220uf 35v 647-UPW1V221MPD 220uf 35v $0.28
awr-156 c23 2200uf 35v 647-UPW1H222MHD 2200uf 50v $1.49 ea
---mouser parts list importer --- cut/paste data entry text block ------
512-KSC2073TU
512-KSA940TU
512-KSC2383YTA
512-KSA1013YBU
512-KSC2073TU
512-KSC2383YTA
512-1N5244B
512-1N5243B
512-1N4748A|2
647-UPW2A4R7MDD|2
647-UPW1V470MED|4
647-UPM2A221MHD|4
647-UPW1V221MPD
647-UPW1H222MHD
right now there is a month lead time on the backordered ksc2383YTA, so ksc2383OTA can be substituted.
about 14 bucks in parts, with another 6 to 8 for shipping.
So:
Replace
awr-156 Q3 2sa850
also because of potential overstress:
awr-156 q4 2sb682
awr-156 d9 mz-130
although considering the effort, a full rebuild of the board will not add much expense or effort, with an increase in reliability.
awr-156 q1 2sd712 100v 4a 30w 55-300hfe 8mhz
512-KSC2073TU npn to-220 bce 150v 1.5a 25w 4mhz 40-140hfe $0.54
awr-156 q4 2sb682 100v 4a 30w 55-300hfe 8mhz
512-KSA940TU pnp to-220 bce 150v 1.5a 25w 4mhz 40-140hfe $0.54
neither side is going to come close to an amp of current, no less 4 amps
awr-156 q2 2sc1735 100v 0.5a 0.8w 55-300hfe 130mhz
512-KSC2383YTA to-92L ecb 160v 1a .9w 50mhz 160-320hfe $0.17
awr-156 q3 2sa850 100v 0.5a 0.8w 55-300hfe 130mhz
512-KSA1013YBU to-92L ecb 160v 1a .9w 50mhz 160-320hfe $0.17 (R=60-120, O=100/200, Y=160/320)
awr-156 Q5 2sd712 512-KSC2073TU
awr-156 q6 2sc945a eCb 50v .15a .25w 300mhz 40-700hfe
512-KSC2383YTA to-92L ecb 160v 1a .9w 50mhz 160-320hfe $0.17
awr-156 d8 mz-140 512-1N5244B Fairchild 14 V, 0.5W Zener
awr-156 d9 mz-130 512-1N5243B Fairchild 13 V, 0.5W Zener
awr-156 d10 LZ230 512-1N4748A Fairchild 22 V, 1.0W Zener
awr-156 d11 LZ230 512-1N4748A Fairchild 22 V, 1.0W Zener
awr-156 c19,c20 4.7uf 50v 647-UPW2A4R7MDD 4.7uf 100v $0.14
awr-156 c17,c18 47uf 16v 647-UPW1V470MED 47uf 35v $0.16
awr-156 c24,c25 47uf 25v 647-UPW1V470MED 47uf 35v $0.16
awr-156 c11,c12,c15,c16 220uf 80v 647-UPM2A221MHD 220uf 100v $1.02 ea
awr-156 c13 220uf 35v 647-UPW1V221MPD 220uf 35v $0.28
awr-156 c23 2200uf 35v 647-UPW1H222MHD 2200uf 50v $1.49 ea
---mouser parts list importer --- cut/paste data entry text block ------
512-KSC2073TU
512-KSA940TU
512-KSC2383YTA
512-KSA1013YBU
512-KSC2073TU
512-KSC2383YTA
512-1N5244B
512-1N5243B
512-1N4748A|2
647-UPW2A4R7MDD|2
647-UPW1V470MED|4
647-UPM2A221MHD|4
647-UPW1V221MPD
647-UPW1H222MHD
right now there is a month lead time on the backordered ksc2383YTA, so ksc2383OTA can be substituted.
about 14 bucks in parts, with another 6 to 8 for shipping.
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D10, D11 got lost in the shuffle, literally.... 22v 1 watt zeners...
awr-156 d10 LZ230 512-1N4748A Fairchild 22 V, 1.0W Zener
awr-156 d11 LZ230 512-1N4748A Fairchild 22 V, 1.0W Zener
I edited them back into the list on that post..
I'm late to the party here, but what a great thread this was/is and extremely helpful to me!
I recently picked up an SX-980 from eBay from a highly rated seller. Very clean, but despite being 're-cap'd' it still has some issues. Phono 1 had a broken ground cap (easy fix) but the protection circuit was tripping when the jams got too serious. I downloaded the manual and adjusted the power amp center current, the idle current and the power meters - all successfully. Still tripping the protection circuit though, but somewhat improved.
One of Mark's helpful suggestions was to look at the terminals at the top of the boards for oxidation/overheating signs, and Bingo! They were all pretty nasty looking. I didn't have a pencil eraser handy, but I made use of some very fine emery board sticks (about 3mm square) for plastic model finishing. This touch-up, followed by DeOxIt on the plugs made a HUGE improvement. I was able to play extended high volume music at steady 20-60W and touching 80W output levels at about all the SPL my ears could stand. The protection circuit tripped one time for 5 sec. over about 15 minutes.
This site is fabulous and the members are super-knowledgeable and the resources share freely.
Thanks!
I recently picked up an SX-980 from eBay from a highly rated seller. Very clean, but despite being 're-cap'd' it still has some issues. Phono 1 had a broken ground cap (easy fix) but the protection circuit was tripping when the jams got too serious. I downloaded the manual and adjusted the power amp center current, the idle current and the power meters - all successfully. Still tripping the protection circuit though, but somewhat improved.
One of Mark's helpful suggestions was to look at the terminals at the top of the boards for oxidation/overheating signs, and Bingo! They were all pretty nasty looking. I didn't have a pencil eraser handy, but I made use of some very fine emery board sticks (about 3mm square) for plastic model finishing. This touch-up, followed by DeOxIt on the plugs made a HUGE improvement. I was able to play extended high volume music at steady 20-60W and touching 80W output levels at about all the SPL my ears could stand. The protection circuit tripped one time for 5 sec. over about 15 minutes.
This site is fabulous and the members are super-knowledgeable and the resources share freely.
Thanks!
The reason for the eraser is to preserve the plating on the pins. Once that is gone the elements have their way. I'm afraid you maybe doing this pin cleaning again sooner that you would like.
Maybe some sort of inhibitor, like the paste they use on car connectors?
Maybe some sort of inhibitor, like the paste they use on car connectors?
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Removal:
https://www.specialized.net/jdv-standard-pneumatic-sp-692-unwrap-tool-20-26-awg-left-right.html
Install/removal:
https://www.digikey.com/product-detail/en/jonard-tools/HW-UW-20/HW-UW-20-ND/5956003
Instructions on wire wrapping and one stop shopping.
https://www.specialized.net/tools/wire-wrap-tools.html
Note:
We never unwrap any wire wrapped pins. All work is done with the harness's connected.
https://www.specialized.net/jdv-standard-pneumatic-sp-692-unwrap-tool-20-26-awg-left-right.html
Install/removal:
https://www.digikey.com/product-detail/en/jonard-tools/HW-UW-20/HW-UW-20-ND/5956003
Instructions on wire wrapping and one stop shopping.
https://www.specialized.net/tools/wire-wrap-tools.html
Note:
We never unwrap any wire wrapped pins. All work is done with the harness's connected.
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I've found a couple of hot spots on the receiver that I'd like to share. It looks like there is one REALLY hot resistor that needs some investigation, along with a previous splice point near the tuner section. The upper right corner is of the R channel amp board. Both sides are pretty equal in temp.
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That is R11, 2700 ohms 1 watt. It's point in the design is intended to get hot, it is dissipating a little over 1/2 of a watt and it is a 1 watt resistor.
It supplies the bias current / voltage for the D9 13v zener diode, and whatever is drawing current at -13 volts from pin 28 of the power supply.
The way a zener diode works to keep a set voltage ACROSS itself is to pull more current until either the voltage is correct, or it burns itself out - thus more draw makes a cooler D9 but a hotter R11. And NO I don't think pin 28 is pulling inordinate amounts of current. It supplies 8 mA (0.008Amp) to run the meter circuitry, and there are no capacitors OFF the board to leak and pull more current.
You'll have to describe the splice more accurately to comment upon it, where each end of each wire is connected to.
The service manual will supply the necessary enlightenment for the description.
It supplies the bias current / voltage for the D9 13v zener diode, and whatever is drawing current at -13 volts from pin 28 of the power supply.
The way a zener diode works to keep a set voltage ACROSS itself is to pull more current until either the voltage is correct, or it burns itself out - thus more draw makes a cooler D9 but a hotter R11. And NO I don't think pin 28 is pulling inordinate amounts of current. It supplies 8 mA (0.008Amp) to run the meter circuitry, and there are no capacitors OFF the board to leak and pull more current.
You'll have to describe the splice more accurately to comment upon it, where each end of each wire is connected to.
The service manual will supply the necessary enlightenment for the description.
