I have had this problem once before but I forgot what I did to solve it. I can only receive stations at 570 and 620 and they spread across the tuning band. The tuning capacitor only makes them stronger or weaker.
That means either the oscillator isn't working right. But when I had this problem before there was nothing wrong with the oscillator circuitry. I can adjust the first IF transformer so that either of the above two frequencies are loud and clear.
I have replaced every paper and every electrolytic filter capacitor in this radio. There are no capacitors left to replace. Everything I measure seems to be in very good condition.
I searched through my previous posts but cannot find where I had this problem before. The IF transformers in this radio aren't the same size as the spare ones I have. I think it was Norm Leal who helped me.
I have tried to get it working for several hours but I can't get anywhere with it. There's not much in that section, so it cannot be a serious problem. This is an AC/DC set. There's very little that can go wrong.
Please help,
Thanks,
Dave
Using my B & K E200D RF signal generator, I was able to set the IF frequency to 456 Kc. That worked just fine. It's weak through the antenna at 1420 and doesn't tune anything. When I set the RF generator to CW, I can make the radio tune fine. So I am pretty sure the local oscillator is missing somewhere.
Thanks,
Dave
:Hello All,
: I have had this problem once before but I forgot what I did to solve it. I can only receive stations at 570 and 620 and they spread across the tuning band. The tuning capacitor only makes them stronger or weaker.
: That means either the oscillator isn't working right. But when I had this problem before there was nothing wrong with the oscillator circuitry. I can adjust the first IF transformer so that either of the above two frequencies are loud and clear.
: I have replaced every paper and every electrolytic filter capacitor in this radio. There are no capacitors left to replace. Everything I measure seems to be in very good condition.
: I searched through my previous posts but cannot find where I had this problem before. The IF transformers in this radio aren't the same size as the spare ones I have. I think it was Norm Leal who helped me.
: I have tried to get it working for several hours but I can't get anywhere with it. There's not much in that section, so it cannot be a serious problem. This is an AC/DC set. There's very little that can go wrong.
:
:Please help,
:
:Thanks,
:
:Dave
When you figure it out - let me know. I have a Zenith that's doing the same thing....
Have you tried another converter tube? Sometimes the converter tube will refuse to oscillate at certain frequencies even if it tests good. I don't have a 6A7 handy to try in mine. But I will have one either later today or tomorrow and let you know if it solved the problem.
I remember having that problem before. I had a radio where I could only receive part of one band but not the other and SW didn't work either. I replaced the tube and all worked perfectly. This was a hot chassis set with a voltage doubler circuit. It had a large chassis too. I don't remember what it was but it may be somewhere in our archives.
If you can't make 455kc then you will receive nothing except accidentally detecting something connected after the pentagrid converter. That would be the closest strongest station.
Another thing that could happen is that the oscillator is working but the mixer part isn't. So the signal can't be moved from the received frequency carrier to the IF frequency carrier.
Anyway, see if replacing the converter tube helps.
Dave
:Dave,
:
:When you figure it out - let me know. I have a Zenith that's doing the same thing....