If you would lift the leg of R428 (the side that is connected to the pre-driver) then take this leg and jumper it
to chassis ground (as per @floriant suggestion) this should simulate a "good" pre-driver stage with 0V DC noise (offset).
Then measure VOP R to see if the value is in the <100mV range rather than 2.5V [2500mV]
If <100mV then the driver/poweramp stage is clean for offset and you can concentrate on the pre-driver (comparator) stage.
to chassis ground (as per @floriant suggestion) this should simulate a "good" pre-driver stage with 0V DC noise (offset).
Then measure VOP R to see if the value is in the <100mV range rather than 2.5V [2500mV]
If <100mV then the driver/poweramp stage is clean for offset and you can concentrate on the pre-driver (comparator) stage.
Victory.
Its was one bad power transistor.
I retested with transistors tester and one 5200 was bad.
Thank you very much.
Amplifier works fine after replacing and bias adjust..
Its was one bad power transistor.
I retested with transistors tester and one 5200 was bad.
Thank you very much.
Amplifier works fine after replacing and bias adjust..
Now its problem of idling current.
Its 100mV... normally...5mV.
At first I managed to adjust 5mV, but after three days it became 100mV.
DC offset OK....0V
Right channel is very hot.
Impossible adjust idling current via VR402.
But Amplifier works fine.
Thanks
Its 100mV... normally...5mV.
At first I managed to adjust 5mV, but after three days it became 100mV.
DC offset OK....0V
Right channel is very hot.
Impossible adjust idling current via VR402.
But Amplifier works fine.
Thanks
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Your initial checking into the protect mode you said that Q415 thru Q417 checked out OK.
Did you verify with a diode test or transistor tester? Could be a weak transistor failing after hours of heat /on-time.
Might be the VR402 is failing?
Also would not pass up checking C411 + C412 (or just replacing if these are crappy caps).
Is the left channel bias maintaining around the 5mV range?
Did you verify with a diode test or transistor tester? Could be a weak transistor failing after hours of heat /on-time.
Might be the VR402 is failing?
Also would not pass up checking C411 + C412 (or just replacing if these are crappy caps).
Is the left channel bias maintaining around the 5mV range?
If bias on the right channel is adjustable to 5mV after 5-10 minutes after power on but then rises dramatically it's gotta be a heat related item.
Q415 thru Q418 and even the final outputs could have a weak device.
Q415 thru Q418 and even the final outputs could have a weak device.
Нет, холодно или жарко, отклонение отрегулировать невозможно.
After power on its start on 100mv and after 2 min 111...112mv
After power on its start on 100mv and after 2 min 111...112mv
That's no good. A part is failing.
I'd do the transistor testing and check C411, C412 for DC leakage.