AC 70 - Clarion TRF

1/14/2005 8:21:34 PMMartin Bednarczuk

I'm trying to diagnose a problem. I turn on the radio and as the tubes start to warm up, it begins to play clearly, and the volume increases. However, once the tubes reach operating temperature the radio begins to howl - a result of a signal feed-back. Being a novice myself I'm not sure what could be the cause. The radio has been recapped before I bought it, but I do not know the full extent of work done. What should I check? Thanks, Martin

1/14/2005 11:22:52 PMNorm Leal

Hi Martin

Are the #24 tubes shielded? Does the howl happen when volume is turned up. Bad bypass caps and lack of tube shielding are usual causes of howl. Some radios howl when volume is turned up high.

http://www.nostalgiaair.org/PagesByModel/692/M0040692.pdf

Norm

:I'm trying to diagnose a problem. I turn on the radio and as the tubes start to warm up, it begins to play clearly, and the volume increases. However, once the tubes reach operating temperature the radio begins to howl - a result of a signal feed-back. Being a novice myself I'm not sure what could be the cause. The radio has been recapped before I bought it, but I do not know the full extent of work done. What should I check? Thanks, Martin

1/17/2005 3:46:12 PMJohn McPherson

If all of those things Norm mentions check out okay, look for a little wiper spring or coil loop from the rotating portion of the tuning condensors to the grounded portion of the frame. The springs might be corroded, or broken.

:Hi Martin
:
: Are the #24 tubes shielded? Does the howl happen when volume is turned up. Bad bypass caps and lack of tube shielding are usual causes of howl. Some radios howl when volume is turned up high.
:
:http://www.nostalgiaair.org/PagesByModel/692/M0040692.pdf
:
:Norm
:
::I'm trying to diagnose a problem. I turn on the radio and as the tubes start to warm up, it begins to play clearly, and the volume increases. However, once the tubes reach operating temperature the radio begins to howl - a result of a signal feed-back. Being a novice myself I'm not sure what could be the cause. The radio has been recapped before I bought it, but I do not know the full extent of work done. What should I check? Thanks, Martin