Hi all,
Amp came dead. No outputs were bad no power supply fets were bad.
Powered up and was pulling 0.4amps. Checked pin1 voltage which was 5.2v and pin 2 was 5.1v. So I removed the outputs and same issue. I removed main rectifiers same issue.
Removed 4080 same issue.
I lifted the voltage divider resistors connected to pin1 with main rectifiers on board and without 4080 and outputs. Amp came on with 1.3Amps stable. Tried to remove the current limiting resistor and it went upto 4.5amps. Main rail voltage from which voltage divider is connected to go to pin 1 of sg3525 is 87v. Is that current draw normal. And what is the pot in the middle of the board use for?
Amp came dead. No outputs were bad no power supply fets were bad.
Powered up and was pulling 0.4amps. Checked pin1 voltage which was 5.2v and pin 2 was 5.1v. So I removed the outputs and same issue. I removed main rectifiers same issue.
Removed 4080 same issue.
I lifted the voltage divider resistors connected to pin1 with main rectifiers on board and without 4080 and outputs. Amp came on with 1.3Amps stable. Tried to remove the current limiting resistor and it went upto 4.5amps. Main rail voltage from which voltage divider is connected to go to pin 1 of sg3525 is 87v. Is that current draw normal. And what is the pot in the middle of the board use for?
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What are you referring to as the current limiting resistors?
When there is only one pot in a class D circuit, it's typically used to null DC offset.
When there is only one pot in a class D circuit, it's typically used to null DC offset.
Without the voltage divider on pin 1 of the driver IC, you lost regulation and the power supply is now producing more voltage than the rating of the rail caps. That's at least part of the excessive current draw.
What's the measured value of Q37 that's connected to it? You may have to desolder it.
Which resistor did you initially remove, R36 or D37?
Which resistor did you initially remove, R36 or D37?
R37 is 50kohms.
I lifted one side of both resistors. Resistors on board not giving proper readings. So I have to lift one leg out of board to read the resistance.
I lifted one side of both resistors. Resistors on board not giving proper readings. So I have to lift one leg out of board to read the resistance.
Go back to the configuration where you had 5.2v on pin 1 and 5.1v on pin 2. What was the rail voltage?
There is very low voltage on pin1 0.25v. Amp tries to pull plenty current and goes into protect. 4080 becoming slightly hot.
Does this amp have pulldown resistors on the output FETs?
For this amp to have 5.2v on pin 1 of the 3525, it would have to have about 65v driven into R37. Is there something else driving pin 1 directly (bypassing the R36/37 voltage divider)?
For this amp to have 5.2v on pin 1 of the 3525, it would have to have about 65v driven into R37. Is there something else driving pin 1 directly (bypassing the R36/37 voltage divider)?
No this amp has no pull down resistors.
Pin1 don't have 5.2v again. Amp goes into protect. There is nothing else connected to pin1.
Pin1 don't have 5.2v again. Amp goes into protect. There is nothing else connected to pin1.