Quote:
Originally Posted by Wind157
Yeah my luck is typically that I break something when fixing it though.
I suppose I should take the meter and check the various caps. It's just replacing the caps in the can, I feel like I'm flying blind without know exactly where to connect the replacement cap. Wish I could just find a replacement can instead of three separate caps.
|
DMMs and solid state meters only check for capacitance...Most paper caps and ~half of lytics fail by leaking DC current across their terminals. A 400V rated cap may only start to leak with 300V or more across it. SolidState meters only apply around 5V to 12V not even close to being able to smoke out the issue. I use a tube type Heathkit C3 cap tester that can check for leakage by applying up to 450V...The only true validation of a vintage cap is applying its full rated voltage to it, and even then most paper caps and vintage lytics are so unreliable that it could(and often does) test good now, then in a week short dead and burn up some unobtainium coil.
No one makes real cans like those (the last vanished in the early 80's), there is one place that makes repops by stuffing individual modern caps into a can (not how the originals were made)...They charge way more than replacing with individual parts and are not worth it. Find your self an original cap that has been removed from a set and look it over carefully...They are not that complicated. Depending on the size of the can there will be 3-4 outer (negative) lugs connected to the outer metal can and 1-4 inner (positive) lugs connected to the center insulating wafer. The can metal is always negative in tube gear as are the outer lugs. The positive lugs in cans that have more than one section are differentiated from each other with the following symbols "^", "D", "[]", "-"(or" ") those symbols will either be scratched on the insulator around the terminals, or will be cut out of the insulator as an enlargement of the hole the positive terminal protrudes from. The metal on the can will have printed on it a label showing in a table the capacitance, voltage and terminal ID symbol of the positive sections. If you or a 5-year-old were in the same room with me and one of those caps I could teach both of you to read and change can caps (assuming prior knowledge of soldering) in around 3 minutes.
The thing about tube sets is they are eventually going to die at random from original caps as long as you leave them in...Better to change them all now one at a time while it works than wait for it to die...If you kill it while working now you can find your mistake easy if you go one or two caps at a time and check after doing those 1-2. But if you wait for the original caps to kill the set and then recap a dead set you have NO way to know you made a mistake...You'll end up changing every single cap and at the end not know if there are other issues or if you screwed up.
I get that a TV can be overwhelming, I try to advise people that want to eventually restore a TV to get a couple of 5 tube AM radios to practice recap work on those first...Much simpler than a TV, forgiving, cheap, and somewhat disposable for tube gear.