I'm going to restuff the Mallory FP 'can' filter capacitor on the Zenith H845 radio.
This is the view from the bottom - not as pretty as the top, huh? It's crowded in there - which is the main reason I'm going to take the can off and restuff it. No way I'd have enough room to put discrete capacitors under the chassis.
The can was probably one of the first things to be mounted to the chassis when the radio was built, and the other components and wiring were added later as it was assembled. Now we need to carefully undo it with all the other wiring around it in place. Lucky us.
I have whole legal pads with scribbling like this. Sometimes I look at them a year later and I'm thinking "what the heck?"
There are four tabs on the can that go through slots in the chassis. You can see them just outside the red circle that's the bottom of the can.
You can also see that big blob of solder on two of the mounting tabs to ensure there's a good ground. That needs to come off before we can remove the can.
The iron will melt that solder in a minute or two. The downside is that it's big, and I need to be careful manuvering it in that small space.
If you look closely, you'll see where I have some solder wick already on the chassis to wick up the solder as it melts.
Cut the can open. I've used hacksaws and Dremels for this, but the last couple I've just rolled the can under a big kitchen knife. Works pretty well, and doesn't leave a big seam like the other methods. But I'm thinking a razor saw with a super fine kerf might be good too.
The stuffing is hazardous, use gloves and dispose of it properly.
The neat thing about this is you can see how the capacitor is made - foil layers wrapped with paper. There's also some kind of dielectric paste in there - that's the hazardous stuff.
I just hack the whole stuffing horizontally right off the base.
The can actually was wired to be the equivalent of 4 separate capacitors. The values of the old capacitors were 80 uF, 40 uF (2) and 50 uF (I think). They were rated at 150 volts, except for the 50 microfarad section, which was rated for 25 volts.
The new Panasonic caps I'm putting in are rated for 250 volts, with the 50 at 50 volts - and at 105 degrees C vs. 85 for the old can. I like to use higher rated caps in these circuits, since the turn-on voltage on the first sections can sometimes exceed 150 volts. Just a little peace of mind. I don't want to do this again any time soon!
You can see how much more compact the modern capacitors are, even with the higher ratings.
You can see how I have shrink insulation on the leads so nothing shorts out.
The grounds are all connected together, and it also passes through a hole near one of the mounting tabs. I'll solder that to the tab and the chassis when I reinstall it.