Hi Julian;
I measured the voltages on pins 1 and 7 on ic’s 5 thru 10 and they are all as you indicated. ?In order to take those measurements I had to remove the AGC board add on, doing so changes things somewhat. The oscillation is a squeal. It some times is present when power is first applied, if the volume is turned down most of the way the squeal goes away but signals can still be heard. When you turn the volume control past about 15 or 20 % the squeal starts, raising the volume doesn’t affect the frequency of the squeal only the volume. Without the AGC circuit the squeal is very intense. ?What I thought was motor boating was not present with the AGC removed, I assume it was the AGC trying to control the volume of the intense squeal. ? When keying the transmitter the squeal stops and the side tone is normal. The squeal returns immediately when receiving. ?This problem has been present from the start. I have been able to conduct some QSO’s by using semi QSK, but once the squeal starts there’s no stopping it. ?I have been able to complete some QSO’s when the received station is strong enough that I can turn the volume below the threshold of the squeal. ?The volume and sensitivity of this receiver seems to be very high. ?I find that I can have the receiver on with no problem the squeal only starts when the transmitter is keyed. I find that the impedance of my head phones is 24 ohms. I tried several other pairs with no effect.
thanks for your interest and time
Bill
