Adjusting trimmer on AVC amplifier?

[vinrads]

Having re aligned the IFT's I came to this one. adjusting C32 it seems to find a null point not a peak, is this correct?

Mick.

[Nuvistor]

What set is it and how are you taking the measurement, I can think of it having a peak or a null depending on the measurement technique?

[ms660]

If the transformer was tuned for maximum signal across it, it would result in maximum AVC voltage which, if the AVC wasn't disabled would result in a null at the measuring point if you're measuring say at the AM det. output or AF output.

Lawrence.

[vinrads]

Hi sorry for the confusion , I am monitoring the audio sig like when aligning the IF's there is a dip in audio which increases when turning the trimmer left or right , i.e the null point. Mick.

[Station X]

I would suggest that's the point at which the AVC comes into operation. In valve sets where the AVC can be turned off, the volume increases when this is done as any AVC controlled stages run flat out.

[ms660]

The last time I tuned an amplified AVC stage I monitored the output of its detector.

Lawrence.

You have found a peak or dip, if it works I wouldn't worry. AGC can do some weird things.

[vinrads]

Thanks all. I have just checked on the other working chassis it's the same, so it appears to be correct.

Thanks, Mick.

[Station X]

Aren't you going to tell us the make and model then?

[ms660]

Midwest 18-36:

https://antiqueradio.org/art/MidwestOwnerManual6.jpg

?

Lawrence.

[majoconz]

If you tune the AGC trimmer for maximum AGC voltage, then you get least audio - that's what AGC is supposed to do.

[vinrads]

Quite right Lawrence ,its the one I had the chassis chrome plated ,here it is so far ,I have the chrome screening cans to fit when I am happy with the performance. Mick.