Replacing Molded Paper Capacitors

[milothicus]

i'm recapping an old reel-to-reel recorder and need to replace the old molded paper capacitors... but what do i replace them with? electrolytics? or some type of film capacitor?

similarly, do i need to replace ceramic tub capacitors?

the recorder is all original from 1955...

[scole]

can you show some pics or lead us to a schematic?

[Enzo]

Use film. A .01uf film cap will work perfectly fine in place of a .01 paper cap.

If the ceramics are not leaky, why replace them?

[milothicus]

well, i don't know if they're leaky, but i know that 50 year old electrolytics and paper caps are likely either leaky now, or will be leaky in the future and should be replaced. i'm just not sure if the caps listed in the parts list as ceramic tub capacitors would be in the same category...

[macpgh]

paper caps

I would replace all the caps as well as all the carbon resistors. Use metal film reistors as they are the quietest & run at a 1% tolerance. Use Either Xicon polyester or SBE polyester caps for all the other caps except the ceramics, but note the voltage for the caps. If they are 400 volt types, you can go with 400 or 600 volt caps. The ceramics should be Ok but it would be more smoother with silver mica caps of the same value & voltage. The lytic caps should be SBE atomics, but they have to be formed on a variac either in circuit or in something else via the variac & then transfered. I often pre-form lytic caps in an old amp & then swap them out. Then depending on your tubes, get NOS telefunkens or buggleboys but be prepared to pay for them as they are pricey. Your unit would be rather high end when done as these are all premium parts, the only hiss you should hear is the tape hiss.
Also in the power supply, use metal oxide resistors that are bigger than the 1/2 watt signal resistors. Flame proof types are also acceptable.
Note that with the unit being rather old, the bands on the resitors may be hard to read as well as the colors my shift hue.
Also note exactly how the coupling caps are positioned & placed as there is a band marking the outer conductor inside the cap & they are specific to the circuit if this is a quality unit....that side goes toward the ground of the circuit even though it might not be specifically going to a direct chassis ground.
You might be better off doing 1 item at a time & working your way thru the chassis.

Good luck


I might be interested in the paper caps when you pull them out. I'm concerned with a .02uf/400 volts or higher cap type.

[Guitarist]

One blues guy we opened for, Larry Howard, has a huge collection of amps. His unique view is to never change anything on a working amp. They came with a sound and stay that way; a historical bias perhaps.
Now, I try and minimize upgrades and rarely toss olde parts
They're also something to said about tweaking/upgrading until it doesn't work anymore. Been there?