[TenTec] 208 CW Filter Howl

[Curt]

I own a 208 CW filter used with an Argonaut 509.  Sometimes on turning the 
rig on with the filter turned on, the audio will squeal.  Turning the filter 
off eliminates the hown, but it returns when the filter is turned on again. 
Only cure is to turn the rig on and off, sometimes several times.  Seems the 
problem is in the filter itself, does this sound like a marginal cap in the 
filter feedback circuit?

Thanks, urt KB5JO