I have a slight problem when receiving a strong AM signal. Some times it will go into feedback and squeal till I turn down the volume. I suspect it may be a microphonic tube. Is there any way other than replacing the tube and will that stop the problem.

When your radio is doing its squealing thing, tap on each tube. If the tube is microphonic it should stop or get worse. There is no fix for a bad tube. Your radio uses the AA5 7 pin tubes. These are cheap to buy, and very common. There are other things that can cause the squeal. Could be in the AVC line, detector, or IF. Even power supply. This link has some basic trouble shooting for suspected caps and resistors that can cause your problem. See the bottom of the page. 1 through 5

http://www.portabletubes.co.uk/sitefiles/restore.htm

:When your radio is doing its squealing thing, tap on each tube. If the tube is microphonic it should stop or get worse. There is no fix for a bad tube. Your radio uses the AA5 7 pin tubes. These are cheap to buy, and very common. There are other things that can cause the squeal. Could be in the AVC line, detector, or IF. Even power supply. This link has some basic trouble shooting for suspected caps and resistors that can cause your problem. See the bottom of the page. 1 through 5
:
:http://www.portabletubes.co.uk/sitefiles/restore.htm
:
:

::When your radio is doing its squealing thing, tap on each tube. If the tube is microphonic it should stop or get worse. There is no fix for a bad tube. Your radio uses the AA5 7 pin tubes. These are cheap to buy, and very common. There are other things that can cause the squeal. Could be in the AVC line, detector, or IF. Even power supply. This link has some basic trouble shooting for suspected caps and resistors that can cause your problem. See the bottom of the page. 1 through 5
::
::http://www.portabletubes.co.uk/sitefiles/restore.htm
::
::
:
:
I found the noisy tube it is the 12BE6 when I tap it it rings.