Help Needed w/ Pioneer SX950

merlynski said:
Different PCB sub-assemblies may have similar component ID labels, you have to pay attention to the proper circuit board identifier as well as the component id. Some times the manufacturer will update their unit during manufacturing and change the assembly number identifier of a pcb that has the same function as the old assembly. As an example "Power Amp" describes a function, the AWH-050 is the identifier for the specific printed circuit board that is the "Power Amp" in this SX-950. If the manufacturer made a major change to a PCB they might call the new one 'AWH-052' but it would still be the "Power Amp". Often times a different letter may be put on a PCB to identify a change of component values installed, while the printed circuit stayed the same. AWH-050-a and AWH-050-b would have the same copper traces but different components installed to improve function. Documentation in the field often does not get updated. Sorry if I got carried away with the explanation :rolleyes:.
Click to expand...
No worried about getting carried away. I'm learning a lot from you all!

As far as the driver transistors, they checked out as well. All measured in the .5-.6v range. What might be the next step?
 
You should still be on DBT, output transistors uninstalled.
If so, then power on, watch the bulb, if it does not flash bright then go dim shut it down, if it goes dim we will test further.
 
merlynski said:
You should still be on DBT, output transistors uninstalled.
If so, then power on, watch the bulb, if it does not flash bright then go dim shut it down, if it goes dim we will test further.
Click to expand...
I actually screwed the output transistors back in before I read your previous reply. Would you like me to unscrew them all?
 
Lexx510 said:
I actually screwed the output transistors back in before I read your previous reply. Would you like me to unscrew them all?
Click to expand...
Yes please. Until we get the unit to pass DBT without them installed it is just a risk of damage to leave them installed
 
Lets try that again.
On the power supply pcb AWR-101, black meter lead to ground, measure with red,
Pin 7, sb +51.5vdc, is:
Pin 10 sb +36.5vdc, is:
Pin 11 sb +28vdc, is:
Pin 13 sb -13.5vdc, is:
Pin 15 sb -13vdc, is:
Pin 14 sb -51.5vdc, is:
Pin 18 sb +49.5vdc unreg, is:
Pin 17 sb -49.5vdc unreg, is:
These voltages may be low because of the DBT.
 
After reporting the power supply voltages, it may be helpful to perform the same 6-way test of the driver transistors for the main outputs, Q9 - Q12 on the AWH-050 board.
 
merlynski said:
Lets try that again.
On the power supply pcb AWR-101, black meter lead to ground, measure with red,
Pin 7, sb +51.5vdc, is:
Pin 10 sb +36.5vdc, is:
Pin 11 sb +28vdc, is:
Pin 13 sb -13.5vdc, is:
Pin 15 sb -13vdc, is:
Pin 14 sb -51.5vdc, is:
Pin 18 sb +49.5vdc unreg, is:
Pin 17 sb -49.5vdc unreg, is:
These voltages may be low because of the DBT.
Click to expand...

Sorry for the silly question, but when you say, "black meter lead to ground, measure with red." Where is ground in this case? I want to be sure before I attempt this. And what setting should the multimeter be on? vdc 200? I want to be sure before I attempt this. Thanks!
 
Lexx510 said:
Sorry for the silly question, but when you say, "black meter lead to ground, measure with red." Where is ground in this case? I want to be sure before I attempt this. And what setting should the multimeter be on? vdc 200? I want to be sure before I attempt this. Thanks!
Click to expand...
Ground is the chassis of the amp, the common point reference for all DC voltages and signals, is the simple answer. The meter setting should be the range that is above the voltage you are measuring, 200 vdc is good for measuring all voltages above 19.5vdc but below 200vdc, 20vdc range is good for all voltages below 20vdc and above 2vdc, if your meter has a 2vdc range use that for voltages under 2vdc.

6-way test for testing transistors: https://audiokarma.org/forums/index.php?threads/bipolar-junction-transistor-testing-basics.43186/

Don't hesitate to ask if you don't understand, we were all new at this at one time :thumbsup:
Be careful, there are lethal AC power line voltages in there.upload_2019-8-31_21-31-49.gif
 
Last edited:
merlynski said:
Lets try that again.
On the power supply pcb AWR-101, black meter lead to ground, measure with red,
Pin 7, sb +51.5vdc, is:
Pin 10 sb +36.5vdc, is:
Pin 11 sb +28vdc, is:
Pin 13 sb -13.5vdc, is:
Pin 15 sb -13vdc, is:
Pin 14 sb -51.5vdc, is:
Pin 18 sb +49.5vdc unreg, is:
Pin 17 sb -49.5vdc unreg, is:
These voltages may be low because of the DBT.
Click to expand...


Pin 7, sb +51.5vdc, is: 45.5
Pin 10 sb +36.5vdc, is: -00.8
Pin 11 sb +28vdc, is: 00.0
Pin 13 sb -13.5vdc, is: -12.6
Pin 15 sb -13vdc, is: -46.1
Pin 14 sb -51.5vdc, is: -46.5
Pin 18 sb +49.5vdc unreg, is: 36.5
Pin 17 sb -49.5vdc unreg, is: -36.6
 
Just for verification, were these measurements taken with the output transistors removed? All 8 of them?
 
Are you still using the 57 watt bulb in the DBT?
As you can see, there are some problems here.
Check all the fuses on the power supply pcb with the ohmmeter (power off).
6-way test Q6, Q1 and Q3, please.
Diode test D11:
Power on DBT:
Measure vdc on the + side of C10, I am expecting about +44vdc on DBT:
Measure vdc on the - side of C11, I am expecting about -44vdc on DBT:
Measure vdc on the cathode of D1, sb about +14.6vdc.

I listed pin 15 wrong, sb -19vdc not -13 (dang fuzzy schematic), but -46vdc is way off.
 
Last edited:
merlynski said:
Are you still using the 57 watt bulb in the DBT?
As you can see, there are some problems here.
Check all the fuses on the power supply pcb with the ohmmeter (power off).
6-way test Q6, Q1 and Q3, please.
Diode test D11:
Power on DBT:
Measure vdc on the + side of C10, I am expecting about +44vdc on DBT:
Measure vdc on the - side of C11, I am expecting about -44vdc on DBT:
Measure vdc on the cathode of D1, sb about +14.6vdc.

I listed pin 15 wrong, sb -19vdc not -13 (dang fuzzy schematic), but -46vdc is way off.
Click to expand...

Yes, still using the 57watt. I didn't have a 100w bulb at home but will purchase one. Is it okay for me to still proceed with the 57w bulb?
 
Lexx510 said:
Yes, still using the 57watt. I didn't have a 100w bulb at home but will purchase one. Is it okay for me to still proceed with the 57w bulb?
Click to expand...

Sure, it won't hurt anything, but it does cause the power supply voltages to sag more while on DBT. I just wanted to be sure so I could compensate/recalibrate my expectations.
I will start on a smaller bulb myself when troubleshooting a unit (more protection), then when I am happy with it on the smaller bulb I will move up to a larger one.

EDIT: more info
 
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merlynski said:
Are you still using the 57 watt bulb in the DBT?
As you can see, there are some problems here.
Check all the fuses on the power supply pcb with the ohmmeter (power off).
6-way test Q6, Q1 and Q3, please.
Diode test D11:
Power on DBT:
Measure vdc on the + side of C10, I am expecting about +44vdc on DBT:
Measure vdc on the - side of C11, I am expecting about -44vdc on DBT:
Measure vdc on the cathode of D1, sb about +14.6vdc.

I listed pin 15 wrong, sb -19vdc not -13 (dang fuzzy schematic), but -46vdc is way off.
Click to expand...

All the fuses check out.
Q1 failed the reverse biasing, showing 1.4-1.8v.
Q6 failed as well, showing 0.1 pretty much all around with the meter beeping.
Q3 checked out fine.

As far as measuring vdc on the capacitors, do I also ground the black lead and test with positive lead?
And how do I measure the cathode of D1?
 
merlynski said:
Are you still using the 57 watt bulb in the DBT?
As you can see, there are some problems here.
Check all the fuses on the power supply pcb with the ohmmeter (power off).
6-way test Q6, Q1 and Q3, please.
Diode test D11:
Power on DBT:
Measure vdc on the + side of C10, I am expecting about +44vdc on DBT:
Measure vdc on the - side of C11, I am expecting about -44vdc on DBT:
Measure vdc on the cathode of D1, sb about +14.6vdc.

I listed pin 15 wrong, sb -19vdc not -13 (dang fuzzy schematic), but -46vdc is way off.
Click to expand...

All the fuses check out.
Q1 failed the reverse biasing, showing 1.4-1.8v.
Q6 failed as well, showing 0.1 pretty much all around with the meter beeping.
Q3 checked out fine.

As far as measuring vdc on the capacitors, do I also ground the black lead and test with positive lead?
And how do I measure the cathode of D1?
 
My internet connection died yesterday, right in the middle of responding.

Lexx510 said:
All the fuses check out. good
Q1 failed the reverse biasing, showing 1.4-1.8v. put it on the replace list
Q6 failed as well, showing 0.1 pretty much all around with the meter beeping. put it on the replace list
Q3 checked out fine.

As far as measuring vdc on the capacitors, do I also ground the black lead and test with positive lead? Yes, you will get a positive voltage on the positive supply filter cap, and a negative voltage on the negative supply filter cap.
And how do I measure the cathode of D1?
Click to expand...
ground the black lead and test with positive lead
 
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