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I have a 1970 Silverface Princeton amp that is a little noisy. I think it may need new caps and a general going through. I am asking advise on the best caps to use. There are rebuild kits available. Some with Orange Drops, some with Mallory 150's or Sozo's, etc. I'm just seeing what people like best.
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When an amp needs to be "re-capped" the caps that need to be replaced are the electrolytic caps, as the electrolytic insulation in the caps will dry out. The caps you mentioned are used to couple stages together or for tone shaping in the EQ section. Those caps do not suffer the same malady of drying out as the electrolytic caps do, so they do not need to be replaced as a maintenance measure. Sometimes these caps will start to leak DC voltage, and at that point they should be changed out. But this never happens to all the caps in the amp at one time, and it is generally considered bad form to just swap all of the coupling and tone caps out in a vintage Fender amp. When they do need to be replaced because they are leaking DC, there is no consensus on "best" caps to use. Any of the caps you listed are fine and will work as well as any others. Magic mojo tone qualities of particular brand names is in the realm of snake oil and magic fairy dust, it is wise to avoid any techs, or cap vendors that try to tell you otherwise. -
Thanks, That simplifies my job a lot. A few vendor sites recommended changing everything (caps and resistors) to bring the amp back to like new spec's. Now would it be wise to test out the various resistors to make sure they are within original tolerances? Or if after replacing the electrolytics, the amp works fine, just leave it be? I suppose a visual inspection of the other caps would be enough. I'm not sure how to test capacitors other than visual unless a cap has gone open and shows dc current going through. I will clean up the tube sockets before anything else. I've been told that can cause noise if loose or some arc is present.Comment
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Yes, it is good practice to measure the resistance of the resistors and replace those that go out of tolerance. Coupling caps can be checked to see if they are passing DC. To do this accurately the downstream lead should be lifted. Vendor sites that recommend blindly replacing all caps and resistors are ones to avoid my friend. They are most interested in parting you with your money, not in preserving vintage amps for best performance and best value.Comment
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Excellent post and agree 100%^^^^KBComment
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