Pioneer SX-950 wont come out of protection

need to figure out whats not working on the supply board .
voltages at q1 q3 and q5 . 9 readings . base collector emitter .. black lead to chassis .
 
Ok, sorry but I dont know where to take those readings since the transistors are deep in the heat sink.
Are you referring to the wires that lead to the transistors?
If so , how can I tell which one is emitter/collector and base ?
 
Ok, sorry but I dont know where to take those readings since the transistors are deep in the heat sink.
Are you referring to the wires that lead to the transistors?
If so , how can I tell which one is emitter/collector and base ?
Look at the service manual, scroll through the pages and you will see a page with all the transistor pin outs labeled B C E
In reply #57, the TO 220 transistor pins are numbered 1 2 3.....1 is the base, 2 is the collector and 3 is the emitter. Hope this helps
 
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Power supply pins
DC Voltage.

1. this is Ground
2. 5.46
3. 5.46
4. 13.83
5. 13.83
6. 52.22
7. 52.22
8. -0.98
9. -0.98
10. -0.98
11. -0.019
12. this is ground
13. -13.4
14. -51.63
15. -19.96
16. -0.023
17. -50.58
18. 50.66
 
Power supply pins
DC Voltage.

1. this is Ground
2. 5.46
3. 5.46
4. 13.83
5. 13.83
6. 52.22
7. 52.22
8. -0.98
9. -0.98
10. -0.98
11. -0.019
12. this is ground
13. -13.4
14. -51.63
15. -19.96
16. -0.023
17. -50.58
18. 50.66

Pin 6 and 7 have the correct voltage, so that eliminates Q1 and Q3. They are good. You need to check Q5 and Q7. That is where the problem is since there is no voltage on Pin 8, 9, 10 and 11. Pins 8, 9 and 10 should have 36.5 volts DC and Pin 11 should have 28 volts DC. The Emitter of Q5 connects to Pin 8, 9, and 10 and should have 36.5 volts DC. It's collector should have 41.7 volts DC and the base should have 37.3 volts DC. The Emitter of Q7 connects to Pin 11 and should have 28 volts DC. It's collector should have 35.2 volts DC and it's base should have 28.7 volts DC. The problem is probably Q5 because Q5 feeds voltage to Q7. It could be a bad resistor in that circuit as well. R6 should have 51.5 volts on one end and 41.7 volts on the other end which connects to the collector of Q5. Let me know what you find.
 
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q1 q3 are fine .
6. 52.22
7. 52.22

q5 is in trouble .
voltages both ends of r6 r7 . dont worry which ends . it should be obvious to see it written down .
 
Pin 6 and 7 have the correct voltage, so that eliminates Q1 and Q3. They are good. You need to check Q5 and Q7. That is where the problem is since there is no voltage on Pin 8, 9, 10 and 11. Pins 8, 9 and 10 should have 36.5 volts DC and Pin 11 should have 28 volts DC.
Can you please clarify where I should be looking for Q5 and Q7 ?
Are they small transistors on the power amplifier or are you referring to the oval output transistors to the heat sink?
 
q1 q3 are fine .
6. 52.22
7. 52.22

q5 is in trouble .
voltages both ends of r6 r7 . dont worry which ends . it should be obvious to see it written down .
Thanks Pete but you are losing me LOL .
What and where are R6 and R7 ?
Resistors ? What board ?
Test voltage or ohms or ?
 
Here are some pics
 

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On the assumption of the readings are from the power supply board I read:

R6 52v DC on both pins
R7 52v DC on one pin and 38.2v DC on the pin near Q5
 
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Thanks Pete but you are losing me LOL .
What and where are R6 and R7 ?
Resistors ? What board ?
Test voltage or ohms or ?
This is on the power supply board. Do you have a schematic? I posted a link for you to get a service manual and a schematic. Did you open it?
 
Hi Pete, I found it, see the info I posted above, thanks for the continued help. Hoping we are onto something
 
Ok, so just like for like ?
Not sure if they have that part number in my local area (Calgary Alberta Canada)
 
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