Quad 606 distortion right channel

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27-Nov-2017 09:12 PM

Cor

Cor

Posts: 2

Hello,

I have a problem with my old 606, the right channel have a distortion. The hole 606 /66 serie is revised a few years ago in Dada's shop (included new capacitors and integrated circuits).

I did some measurements on the unit, I feed the input with 70mV sinus test signal 1 kHz. The output is connected to 6.3 ohms 100W resistors.

I have some oscilloscoop pictures where you can see that, the sinus output signal on the negative side of the sinus is good, the positive side has half way a step in the sinus and has not the hight which it has to be. It is also not stabile, some time the output signal is correct and it flipper between correct and not correct. I don't know how to put the scope pictures on this side.

I see that in the revision, some years ago, that the capacitor C7 is changed from 47 uF to 100uF (63V), I think that is no problem? or the reason of the distortion. The supply voltage on the circuit  is 57.9 V and the buffer capacitor voltage is with 63V (this has no great tolerance). 

The voltage on the on the IC1 output is not -115mV but only -28mV+/- (If the output is correct it is -11mV).

Question: With this description, is it possible to give a hint where I can find the fault in the circuit.

With kind regards

Cor


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27-Nov-2017 11:58 PM

Not Available

Posts: 7

Hi,

Measure the resistors in the +DC and the -DC power lines of the regulator opamp.

They might look OK but I had one in my 306 which was infinite causing a DC shift.

Check topic 306 M12890-6 Upgrade and Fix dd 26 April 2017.

Hope this helps.

Harry

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