farnsworth BT600 new volume problem

Hi Guys I have a Farnsworth BT600 that I recapped replaced a shorted tube and replaced on off volume control. I thought I had it working great. The problem is that weak long distance stations can be heard for about 10-15 seconds when the radio is first turned on and the sound gets lower and lower till it cant be heard. I can turn the radio off and back on and hear the weak station for about 10-15 seconds at that time only strong local stations on the am band can be heard. I have a long wire antenna. Thanks in advance for the help.

Welcome to TRF. Sou nds like either tuner plates may be shorting out, or, look for off value resistors, or, leaky mica capacitors.
Hope this helps....

Thanks Bill Cahill for the reply your suggestion of tuner plates shorted out reminded me that when I first started working on this radio that one section of the three gang tuning cap plates hit together and two or three plates broke off. I wasn't worried about it because the radio appeared to work ok. Could that cause this problem ? Thanks again for the help