01-22-2008, 11:57 PM
Hi Chris,
I am not sure about the motorboating issue someone else may have an idea. I did have one set than had that low rumble and added capatitance to one of the filters cleared it up.
On issues like this I take out the highlighter and trace the circuit again, in case I made a mistake or someone else "worked on" with the set before.
Check the resistors also, if possible lift one side of those you suspect to get a more accurate reading.
http://www.nostalgiaair.org/Resources/675/M0013675.htm
You had said that there was signal on AM and not AM, maybe you meant FM
I had a Truetone a couple months ago that would not receive FM, AM was fine. The bandswitch actually turned on current to the "FM tubes" when the switch was changed. Good cleaning of the bandswitch cured that issue.
I would run thru the test they suggest in the guide. I see they have it broken up in to the stages. If you are able to receive audio then I assume that section would be ok. Touching the center of the volume control with something should make a nice loud buzz. (Make sure you use safe procedures for doing this).
I also see there are some good voltage checks to perform. I would do those. But I must warn you that I am not that good on diagnosing oltage readings, and if the tube is at 'cutoff' or if the grid volts are right. etc...
But it might give an indication of what section does not have the correct voltages, the go from there.
Did you get anything on the FM band? Is the antenna system connected correctly? Some of the old FM sets needed an good antenna for reception. A length of wire, maybe 4 or 5 ft long should work to bring something in.
OK Will check back later, good luck.
Gary.
I am not sure about the motorboating issue someone else may have an idea. I did have one set than had that low rumble and added capatitance to one of the filters cleared it up.
On issues like this I take out the highlighter and trace the circuit again, in case I made a mistake or someone else "worked on" with the set before.
Check the resistors also, if possible lift one side of those you suspect to get a more accurate reading.
http://www.nostalgiaair.org/Resources/675/M0013675.htm
You had said that there was signal on AM and not AM, maybe you meant FM
I had a Truetone a couple months ago that would not receive FM, AM was fine. The bandswitch actually turned on current to the "FM tubes" when the switch was changed. Good cleaning of the bandswitch cured that issue.I would run thru the test they suggest in the guide. I see they have it broken up in to the stages. If you are able to receive audio then I assume that section would be ok. Touching the center of the volume control with something should make a nice loud buzz. (Make sure you use safe procedures for doing this).
I also see there are some good voltage checks to perform. I would do those. But I must warn you that I am not that good on diagnosing oltage readings, and if the tube is at 'cutoff' or if the grid volts are right. etc...
But it might give an indication of what section does not have the correct voltages, the go from there.
Did you get anything on the FM band? Is the antenna system connected correctly? Some of the old FM sets needed an good antenna for reception. A length of wire, maybe 4 or 5 ft long should work to bring something in.
OK Will check back later, good luck.
Gary.
