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2385 reconnect PS00 to P400 pin question

If you put an oscilloscope on the L channel speaker output and you input a sine wave, can you see the distortion on the scope.
 
dankik said:
If you put an oscilloscope on the L channel speaker output and you input a sine wave, can you see the distortion on the scope.
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Yes I can see quite a difference on the left positive lead using sine wave
 
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I think what you need to do is trace the signal back on the Main Amp board to find out where the distortion starts (or start at the input to the board and work forward.
You can compare the same location on L to R channel also for a comparison.
 
Do you mean follow from the input to Aux? so P400 board . If so can I remove PS00 and jump for better access to all connections.
 
What resistor would I need to connect for a dummy load on the speaker terminals
I've got two 100 watt 8 ohm resistors . I was thinking of connecting with alligator clps
 
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That should be fine, but you don't need to drive it that hard to see the distortion (I am assuming it is always there).
I would start with the L channel input to the P700 at J709 and work your way to the output at J713.
(This amp design is too complicated for me to find the signal path, but I think the main path is shown in lt blue.)
See where the signal starts to distort.

1788462784250.png
 
dankik said:
That should be fine, but you don't need to drive it that hard to see the distortion (I am assuming it is always there).
I would start with the L channel input to the P700 at J709 and work your way to the output at J713.
(This amp design is too complicated for me to find the signal path, but I think the main path is shown in lt blue.)
See where the signal starts to distort.

View attachment 3829425
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Wave at J709 is normal
Wave at J713 is flat on the bottom, only half wave
 
sendust said:
Wave at J713 is flat on the bottom, only half wave
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???? Why don't you hear this distortion when you connect the Main Amp In to your other amp's PreOut?
Can you connect it back up with the 2275 PreOut connected to the 2385 Main In, then put your scope on J713 and see if you see the same flat bottom signal.
If it is "really" one-half of a sine wave, then one side of the transistors is not working. If the entire bottom half is missing it is the negative side of the amplifier.
 
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dankik said:
???? Why don't you hear this distortion when you connect the Main Amp In to your other amp's PreOut?
Can you connect it back up with the 2275 PreOut connected to the 2385 Main In, then put your scope on J713 and see if you see the same flat bottom signal.
If it is "really" one-half of a sine wave, then one side of the transistors is not working. If the entire bottom half is missing it is the negative side of the amplifier.
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I connected 2275 pre outs to 2385 main in
Used sine wave J709 full wave, J713 half wave flat on bottom
Used radio , left and right channel perfect clear sound
 
In the past i removed the P400 board to check for issues, i marked all of the connectors, if i installed one in reverse could it cause an issue on only one channel?
 
Let me ask a different way. Looking on your oscilloscope, what is the time from peak to peak?
And what is the frequency of the signal that is going into the amplifier?
 
When using the FM radio instead of sine wave on J 713 I get no wave , on J714 I get a crazy looking wave. If I change settings on scope maybe I would see something but left and right are not the same
 
sendust said:
Used radio , left and right channel perfect clear sound
Click to expand...
sendust said:
When using the FM radio instead of sine wave on J 713 I get no wave , on J714 I get a crazy looking wave.
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I don't understand... before you said if you used the radio, both channels had good clear sound.
But now you get no wave?
What do you hear on the speakers with the FM radio playing if you have no wave on J713? Is it a scope sync problem?
 
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