drspiff
Fisher "T" Aficionado
Mostly because I can I snapped a couple of pictures to give people some idea about the composition of a capacitor and size comparisons between new and old electrolytics:
1) This shows the composition of a foil film capacitor from mid to late 60's. You'll notice the cap is composed of a piece of film with a waxed paper separator. The leads are attached to/laid next to the foil. The foil and paper separator are one continuous length. I suspect that this cap, if unrolled, would stretch several thousands of feet if not more. The foil is about 0.0005" thick and the paper about the same. The capacitance happens due to the paper dielectric maintaining a space between the foil layers. This particular cap came out of an AR 2ax speaker crossover. It is actually a dual cap having 4uf and a 6 uf section.
2) This is a photo of the size differences between old and new caps. The cardboard cap on the right is a 2 section unit with 2 1000uf/35v sections. On the left are 2 1000uf/35v caps. The quarter will provide scale and allow you to compare the sizes. You'll notice that the modern caps are significantly smaller that the older cap. Specifically, Excel tells me that the new cap has a volume that is 6.4% of the old cap. The question sometimes comes asking about when to recap. Notice the discolaration on the lower part of the cardboard cap. Yep, that's leakage and recapping is required. BTW this old cap is the power supply cap from a Fisher late model 400 tube receiver, so figure it is 45 to 50 years old.
I hope these pictures help to answer some of the questions that come up about caps.
1) This shows the composition of a foil film capacitor from mid to late 60's. You'll notice the cap is composed of a piece of film with a waxed paper separator. The leads are attached to/laid next to the foil. The foil and paper separator are one continuous length. I suspect that this cap, if unrolled, would stretch several thousands of feet if not more. The foil is about 0.0005" thick and the paper about the same. The capacitance happens due to the paper dielectric maintaining a space between the foil layers. This particular cap came out of an AR 2ax speaker crossover. It is actually a dual cap having 4uf and a 6 uf section.
2) This is a photo of the size differences between old and new caps. The cardboard cap on the right is a 2 section unit with 2 1000uf/35v sections. On the left are 2 1000uf/35v caps. The quarter will provide scale and allow you to compare the sizes. You'll notice that the modern caps are significantly smaller that the older cap. Specifically, Excel tells me that the new cap has a volume that is 6.4% of the old cap. The question sometimes comes asking about when to recap. Notice the discolaration on the lower part of the cardboard cap. Yep, that's leakage and recapping is required. BTW this old cap is the power supply cap from a Fisher late model 400 tube receiver, so figure it is 45 to 50 years old.
I hope these pictures help to answer some of the questions that come up about caps.
Heck, caps aren't THAT expensive, and I now think that should be done as soon as you know your pots & switches function, on a new toy. :yes: I've been saving old caps, thinking the good ones (?) were worth reusing, but that was just a bit of foolishness, in the learning process. :nono: 
