This amp has very low and distorted output..
Can barely hear the audio have to put ear next to speaker in order to hear it..
I tryed unpluging the preamp board and repluging it back in no difference..
On all the op-amps on the preamp board i get the following voltages on pins 4 and 8 of all of them ..
Pin 4:-8.15
Pin 8:5.15
Also noticed this..
Is this repairable or not really??
If so where do i start?
Can barely hear the audio have to put ear next to speaker in order to hear it..
I tryed unpluging the preamp board and repluging it back in no difference..
On all the op-amps on the preamp board i get the following voltages on pins 4 and 8 of all of them ..
Pin 4:-8.15
Pin 8:5.15
Also noticed this..
Is this repairable or not really??
If so where do i start?
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It appears that that resistor is being substituted for the one with the burned pads under it. If I'm not mistaken, U801 drives the two transistors to the right of your arrow. Those transistors drive the resistor which drives the transistor.
Does it appear that the FET has been replaced?
Do you see a clean square wave on the bases and the emitters of the two transistors?
Does it appear that the FET has been replaced?
Do you see a clean square wave on the bases and the emitters of the two transistors?
It appears that the fet has been replaced..
I get a clean square wave on the base and emitter of both transistors
I get a clean square wave on the base and emitter of both transistors
What is the amplitude of the drive signal on the emitter of the two small transistors and on the gate of the FET?
Is it still clean on the gate leg of the FET?
Is it still clean on the gate leg of the FET?
That's probably too low. Are you sure that your scope is reading correctly?
What is the amplitude on the base of the driver transistors?
What is the amplitude on the base of the driver transistors?
Confirm that the large SMD resistors between the filter caps near the yellow transformer are within tolerance.
What's the DC voltage measured directly across each one?
What is the DC voltage on the positive and negative speaker terminals with the black probe on the main ground?
What is the DC voltage on the positive and negative speaker terminals with the black probe on the main ground?
I get no rail voltage
U804 On th main board in front of the yellow transformers is getting red hot
U804 On th main board in front of the yellow transformers is getting red hot
Are you sure that the power supply isn't blown?
U804 is a pair of driver transistors that drive the driver transformer that drive the power supply FETs.
Apply remote and remove it. You should have regulated voltage for about 5 seconds. Does the regulated voltage on the op-amps go to ±15v in that 5 seconds?
U804 is a pair of driver transistors that drive the driver transformer that drive the power supply FETs.
Apply remote and remove it. You should have regulated voltage for about 5 seconds. Does the regulated voltage on the op-amps go to ±15v in that 5 seconds?
All the power supply fets test good ..
If i apply remote then remove it voltage on pins 4 and 8 remain the same so no not getting + - 15 volts
Not sure if anything else in the supply is bad but the fets test fine
If i apply remote then remove it voltage on pins 4 and 8 remain the same so no not getting + - 15 volts
Not sure if anything else in the supply is bad but the fets test fine
Compare the resistance reading across the internal transistors of the two driver ICs. Look up the datasheet to see how the internal transistors are configured.
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