I recently purchased a 73 Princeton Reverb from the forum. It sounds very good to me but seems to have a reverb problem. The reverb sounds sort of "gated" and not lush or full. There is very little variation in the amount of reverb as I twist the knob. I had a 78 Princeton, I think, that had very nice reverb and currently have a 76 Super Reverb which has great reverb as well. There is also a high whistle, almost microphonic sound when the reverb is cranked on my new 73. The original tank in my Super has been replaced due to corrosion in the original. I tried plugging the reverb from the Super into the Princeton and got no reverb at all. I'd appreciate any clues as to what to look for.