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pioneer sx-580

Randy007

Randy007

Well-Known Member
I have a nice Pioneer sx580 I aquired with the left channel not working...I thought it was the STK029 module, when I took the right channel module and inserted it in the left channel. Still nothing, but I did notice that the Power meter on the left channel was peging out at max power. Here are the voltages on the I think good power module..when installed
P1 (L) 31.5v P1 (R) 30v
P2 -31.26v P2 -31v
P3 30v P3 30v
P8 30v P8 30v
P9 30.6v P9 30.6v
P0 31v P0 31v

now here are the voltages with no modules
P1 L 8.5v P1 R 8.48v
p2 -32v p2 -32v
p3 .018v p3 .15v
p8 .019 p8 32v
p9 32v p9 32v
p0 52.1v p0 51.4


right channel works w/headphones, I have not hooked to speakers and I am using a DBT

any help would be appreciated...thanks
 
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Get a pair of resistors of the same value, 270Ω to 1kΩ (not critical) and solder them to the pins on the foil side of the board, as shown, without the module installed.
Power up and measure dcv on pins 1 and 0, they should be roughly equal in voltage, but opposite polarity, 0 should be plus and and 1 should be minus.
Pins 3 and 8 should be identical, and very close to 0vdc..



STK_removed_power_amp.jpg
 
thanks for response, 330ohm resistor soldered pin 1 10vdc pin 0 12.21
pin 3 10.2v pin 8 10.12
voltages are way to high
 
You are welcome.
You have one resistor from pin 0 to pin 8, and another resistor from pin 1 to pin 3?
The voltage there is not the critical measurement, the fact that they are + and - balanced around 0vdc is important for pins 1 and 0. You did not put the polarity on your measurements, that is a critical part of a dcv measurement.
 
High voltage without the STK in place (substatially different than zero either plus or minus) on pin 1, the signal input, indicates a shorted driver or differential pair. This will "rail" the STK to full output voltage and often fry it.

This was the case on my Kenwood KA-80. Also check both STKs for shorts from either rail to the input or output. Common failures. Note that a shorted STK will also fry the driver and driver emitter resistors.
 
The resistors in place of the STK close the dc feedback path and indicates whether the diff amp is controlling the output dc level at pins 3 and 8. The voltages on pins 0 and 1 tell if the constant current sink (and voltage gain) transistor circuit is working correctly.
The driver/output transistors and their resistors are inside the STK module, along with the fixed bias spreader circuit.
 
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Lol, that's what I meant, given my small understanding of amplifier circuits! Same issue in a Yamaha R-700 at the moment, the 3056 voltage amp STK is bad and feeds full voltage to the signal input of the STK0050II. Full rail voltage on the speaker outputs.
 
merlynski said:
You are welcome.
You have one resistor from pin 0 to pin 8, and another resistor from pin 1 to pin 3?
The voltage there is not the critical measurement, the fact that they are + and - balanced around 0vdc is important for pins 1 and 0. You did not put the polarity on your measurements, that is a critical part of a dcv measurement.
Click to expand...
sorry, the readings are pin 1- +22.47v pin 0- +23.66v pin 3- +22.54v and pin 8- +22.50v

thats strange because the voltages I just took are different than the first readings. any idea?

also, should I have anything connected to the inputs and should I be on a dummy load?
 
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OK, now we are getting somewhere! :cool:
No input signal, input set to Aux, volume at minimum, tone controls centered or off, balance centered, no loads or speakers connected.
Test Q303; R345, 100Ω; R317, 100Ω; dual transistor Q301. R410, 100Ω.
Power on if all those test good.
Measure dcv on the - side of C415, should be -26.6vdc
Measure dcv on the PCB at STK pin 9, +28vdc; pin 2, -28vdc verify power supplies.
Measure dcv on the base of Q303, sb -25.3vdc, emitter sb -25.9vdc.
Measure dcv on the + side of C301, sb +0.1vdc.
 
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merlynski said:
OK, now we are getting somewhere! :cool:
No input signal, input set to Aux, volume at minimum, tone controls centered or off, balance centered, no loads or speakers connected.
Test Q303; R345, 100Ω; R317, 100Ω; dual transistor Q301. R410, 100Ω.
Power on if all those test good.
Measure dcv on the - side of C415, should be -26.6vdc
Measure dcv on the PCB at STK pin 9, +28vdc; pin 2, -28vdc verify power supplies.
Measure dcv on the base of Q303, sb -25.3vdc, emitter sb -25.9vdc.
Measure dcv on the + side of C301, sb +0.1vdc.
Click to expand...
Looks like R410 is burned....
 
HPMguy said:
High voltage without the STK in place (substatially different than zero either plus or minus) on pin 1, the signal input, indicates a shorted driver or differential pair. This will "rail" the STK to full output voltage and often fry it.

This was the case on my Kenwood KA-80. Also check both STKs for shorts from either rail to the input or output. Common failures. Note that a shorted STK will also fry the driver and driver emitter resistors.
Click to expand...

Curious as to why you would jump in to the middle of this? And why you would tell OP to check for shorts without telling him how?
 
merlynski said:
OK, now we are getting somewhere! :cool:
No input signal, input set to Aux, volume at minimum, tone controls centered or off, balance centered, no loads or speakers connected.
Test Q303; R345, 100Ω; R317, 100Ω; dual transistor Q301. R410, 100Ω.
Power on if all those test good.
Measure dcv on the - side of C415, should be -26.6vdc
Measure dcv on the PCB at STK pin 9, +28vdc; pin 2, -28vdc verify power supplies.
Measure dcv on the base of Q303, sb -25.3vdc, emitter sb -25.9vdc.
Measure dcv on the + side of C301, sb +0.1vdc.
Click to expand...

-side of C415 -31vdc
pin 9 +31vdc
pin 2 -31vdc
Q303 base -29vdc
emitter -30vdc
+ side C301 +.4vdc
I replaced R410
 
If R410 burned Q301, Q303, R345, R317 are likely affected.
Measure dcv on the collector of Q303.
Did you measure R345 and R317?
Test Q301, it is a dual transistor.
 
merlynski said:
If R410 burned Q301, Q303, R345, R317 are likely affected.
Measure dcv on the collector of Q303.
Did you measure R345 and R317?
Test Q301, it is a dual transistor.
Click to expand...

Here are my readings, now this is without the module correct? also I noticed Q303 has been replaced with a KCS2690
R317 150 OHMS
R345 100 OHMS
Q303 COLLECTOR -28VDC
Q301 B -7.5VDC
C -29VDC
E -19VDC
C -28.5VDC
B -19VDC
 
This is without the module but with the resistors in place for troubleshooting purposes.
I see conflicting readings here: + of C301 is reported as +0.4vdc in post #12. This point should be common to one of the bases of Q301, but neither of them is that voltage in post #14. The common emitter pin of Q301 sb about +0.7vdc.
I would also expect the collector of Q303 to be about (roughly) -5 to -8 vdc with those resistors in place.
KSC2690 is a good choice for that replacement.
What is the dcv on the + side of C336? I expect about +12 or +13vdc, cannot find a listing for the voltage of D309 in my SM copies.

Did you do a 6-way diode test of Q303 and Q301?
 
merlynski said:
This is without the module but with the resistors in place for troubleshooting purposes.
I see conflicting readings here: + of C301 is reported as +0.4vdc in post #12. This point should be common to one of the bases of Q301, but neither of them is that voltage in post #14. The common emitter pin of Q301 sb about +0.7vdc.
I would also expect the collector of Q303 to be about (roughly) -5 to -8 vdc with those resistors in place.
KSC2690 is a good choice for that replacement.
What is the dcv on the + side of C336? I expect about +12 or +13vdc, cannot find a listing for the voltage of D309 in my SM copies.

Did you do a 6-way diode test of Q303 and Q301?
Click to expand...
no I did not, I will and get back....thanks for all your help
 
I FIGURED IT OUT....I think Q301 is bad...
B/E STEADY BEEP NO READING
B/C .592
E/B STEADY BEEP NO READING
C/B 1.01
C/E .592

OTHER SIDE
B/E .659
B/C .641
E/B O/L
C/B O/L
C/E O/L
 
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