This is rather embarrassing. I have rebuilt around 50 Pioneer SX-1050's, and have never had reason to check pin out voltages from the Power Amp board to the output transistors. Pins 21-24, then pins 25-28, then pins 29-32, and the last one pins 33-36. The voltages I am getting on this particular unit can't possibly be right, and I don't want to wait until I get another 1050 in house. Thanks in advance to anyone out there, Hank!
Pin out voltages on SX-1050 PA board output transistors
- Thread starter HankM
- Start date
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well, didn't you download a service manual? With those types of numbers, expectations tend to get raised, stuff rubs off on ya, and so forth... because all of this stuff that isn't off the cuff, comes from the service manual.
I'll stick in a little extra info, to illuminate things a bit.
Plus, this isn't like most push-pull amps, where the npn drivers (emitters) are loaded by the PNP driver on the mirror side of the driver, instead the emitter load is a resistor (with plenty of wattage) connected to the opposite rail. Thus the PNP side can be all cattywumpus while the npn side is unperturbed and behaving. This can get some pretty big voltage differences between the pnp and npn outputs (usually they are pretty close together - relatively speaking). Then to top it off, the base drives for the output transistors have a 10 ohm series resistor in that line.
BTW, the pins have been shined up, for good contact?
Right Channel
21 +62v unregulated DC, shared collectors of the NPN output transistors, same voltage as the big main caps...
22 +0.00v + 1/2 idle current, individual emitter of one of the NPN outputs, to 0.5 ohm resistor
23 +0.00v + 1/2 idle current, individual emitter of another NPN outputs, to 0.5 ohm resistor
24 +0.600v shared bases of the NPN output transistors
25 -62v unregulated DC, shared collectors of the PNP output transistors, same voltage as the big main caps...
26 -0.00v - 1/2 idle current, individual emitter of one of the PNP outputs, to 0.5 ohm resistor
27 -0.00v - 1/2 idle current, individual emitter of another PNP outputs, to 0.5 ohm resistor
28 -0.600v shared bases of the PNP output transistors
Left Channel
36 +62v unregulated DC, shared collectors of the NPN output transistors, same voltage as the big main caps...
35 +0.00v + 1/2 idle current, individual emitter of one of the NPN outputs, to 0.5 ohm resistor
34 +0.00v + 1/2 idle current, individual emitter of another NPN outputs, to 0.5 ohm resistor
33 +0.600v shared bases of the NPN output transistors
32 -62v unregulated DC, shared collectors of the PNP output transistors, same voltage as the big main caps...
31 -0.00v - 1/2 idle current, individual emitter of one of the PNP outputs, to 0.5 ohm resistor
30 -0.00v - 1/2 idle current, individual emitter of another PNP outputs, to 0.5 ohm resistor
29 -0.600v shared bases of the PNP output transistors
I'll stick in a little extra info, to illuminate things a bit.
Plus, this isn't like most push-pull amps, where the npn drivers (emitters) are loaded by the PNP driver on the mirror side of the driver, instead the emitter load is a resistor (with plenty of wattage) connected to the opposite rail. Thus the PNP side can be all cattywumpus while the npn side is unperturbed and behaving. This can get some pretty big voltage differences between the pnp and npn outputs (usually they are pretty close together - relatively speaking). Then to top it off, the base drives for the output transistors have a 10 ohm series resistor in that line.
BTW, the pins have been shined up, for good contact?
Right Channel
21 +62v unregulated DC, shared collectors of the NPN output transistors, same voltage as the big main caps...
22 +0.00v + 1/2 idle current, individual emitter of one of the NPN outputs, to 0.5 ohm resistor
23 +0.00v + 1/2 idle current, individual emitter of another NPN outputs, to 0.5 ohm resistor
24 +0.600v shared bases of the NPN output transistors
25 -62v unregulated DC, shared collectors of the PNP output transistors, same voltage as the big main caps...
26 -0.00v - 1/2 idle current, individual emitter of one of the PNP outputs, to 0.5 ohm resistor
27 -0.00v - 1/2 idle current, individual emitter of another PNP outputs, to 0.5 ohm resistor
28 -0.600v shared bases of the PNP output transistors
Left Channel
36 +62v unregulated DC, shared collectors of the NPN output transistors, same voltage as the big main caps...
35 +0.00v + 1/2 idle current, individual emitter of one of the NPN outputs, to 0.5 ohm resistor
34 +0.00v + 1/2 idle current, individual emitter of another NPN outputs, to 0.5 ohm resistor
33 +0.600v shared bases of the NPN output transistors
32 -62v unregulated DC, shared collectors of the PNP output transistors, same voltage as the big main caps...
31 -0.00v - 1/2 idle current, individual emitter of one of the PNP outputs, to 0.5 ohm resistor
30 -0.00v - 1/2 idle current, individual emitter of another PNP outputs, to 0.5 ohm resistor
29 -0.600v shared bases of the PNP output transistors
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