Projects > Power amplifiers

QRP02 DC out

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peranders:
To disconnect DC servo, just short R20. If the offset goes down to low values the problem is around the servo, if not sometihng elsa is wrong.

The servo has +- 12 volts?

Pin 5 and 6, IC1  are at zero volts?

When you have +32 volts out, do you have -10 volts out from the DC servo?

Give me some more measurements and I'll may be able to figure out the problem. Have you built one or two working units? If two, are the alike, both putting out 32 VDC?

AudioSpirit:
I short r20 ,didn't help.Both boards have a same problem.

I have 0 v on pins 5 and 6 ,but on servo out i have just 0,9 v instead
of -10v. Also when I just touch with hand pin10, voltage going down from +32
to +28 volt.

AudioSpirit:
I short r20 ,didn't help.Both boards have a same problem.

I have 0 v on pins 5 and 6 ,but on servo out i have just 0,9 v instead
of -10v. Also when I just touch with hand pin10, voltage going down from +32
to +28 volt.

AudioSpirit:
I short r20 ,didn't help.Both boards have a same problem.

I have 0 v on pins 5 and 6 ,but on servo out i have just 0,9 v instead
of -10v. Also when I just touch with hand pin10, voltage going down from +32
to +28 volt.

peranders:
Do you really have zero ohms between pin 10 of LM3886 and ground?

Since the servo is out of feedback you must have plus or minus 0.6 volts at pin 6. Did you have +32 volts out?

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