multicapacitor disassembly

[milothicus]

I have an old reel to reel recorder that i'm trying to refurbish and am having trouble with some real estate in the chassis.

i took out the old multicapacitor, and because of space considerations and the way it was wired, it would be nice to put some new capacitors in the old can. i've seen this mentioned in a lot of places, but i'm hesitant to start cutting into the can to open it because i have no clue what i'll see inside...

does anyone have some photos of a can opened up? is there a standard way of opening these things?

[PRNDL]

A much better idea would be to get a JJ 40/20/20/20 can. They're inexpensive ... about $15.

Vintage looks is pretty much the only reason you replace the insides of a cap can.

[milothicus]

The old can is 40-30-10-10 @ 450v.

i already have discrete caps to put in, but no space in the chassis, so i was hoping to put them in the same space as the can. next logical step is to put the original can over top of them...

so does anyone have experience with gutting these cans? there's no obvious way into the can. i mean no bent tabs or anything easy, so i need to know what's going to happen if i cut into the can.

[stokes]

Try prying the top of the can off,where the terminals are.

[trevorus]

Why not electrically disconnect the can and leave it in place, then just put the caps inside the chassis. Modern caps are much smaller at the same values, so you should have room. You could even mount a small eyelet board to hold the caps.

[J Martin]

Just get a new can and be done with it. The only reason to use individual caps is if you going to improve the ground paths.

[Regis]

Why not electrically disconnect the can and leave it in place, then just put the caps inside the chassis. Modern caps are much smaller at the same values, so you should have room. You could even mount a small eyelet board to hold the caps.

I've seen this done before, I've done it with a Silvertone I have.

Also, Ted Weber sells cap cans in different values and will build one with any values you need. I think they're around twenty bucks.

[TD_Madden]

Ted's can-caps are limited to 500V.

[milothicus]

i really can't leave it in place because the chassis is so thin stuffing the caps in around the base of the can would be difficult. I also want to use the caps i already bought rather than buying a new can, simply because i can't justify the cost.

i started prying at some edges and did get the can apart and emptied. not very hard to do at all. took no more than 15-20 minutes, and that was being fairly careful.

now, of course, the individual capacitors don't look like they'll fit inside the old can very easily.

i took some pictures of the parts i'll put them up for anyone that later wants to see the insides of a multicapacitor.

[milothicus]

on a related note, the can seemed to be wired incorrectly.

the schematic actually indicates the cap can marking (square, triangle, circle), but the shape and capacitance pairings on the can don't agree with the pairings on the schematic. the wiring looks like it matches the schematic's shapes, but not the values.

i'm assuming i should rewire it to match the values on the schematic, not the shapes.

where the 5 caps should be 40-40-30-10-10, it looks like the wiring ended up being 40-10-40-30-10. what effect would this have on the operation of the recorder?

[trevorus]

Hard to say what the effect would be without a schematic.

[Enzo]

The new individual caps don't necessarily need to be mounted right at the old can cap. Usually, from the cap can, a wire trails off to some point in the circuit. The new cap can be connected at the other end of that wire just as well as at the can. SO the new caps might well wind up spread around the area instead of all at the location of the can.

[Regis]

The new individual caps don't necessarily need to be mounted right at the old can cap. Usually, from the cap can, a wire trails off to some point in the circuit. The new cap can be connected at the other end of that wire just as well as at the can. SO the new caps might well wind up spread around the area instead of all at the location of the can.

I did just this with my Silvertone 1482, have a look.

[milothicus]

there is some space near the other end of the chassis... would i have to worry about interference with these wires? they're carrying some ripple, right?

[Enzo]

For the most part, ripple doesn't radiate, it infects circuits when it shares copper. That is to say don't put the main filter at the far end of the circuit so its ground return shared wiries with the input stage ground. But grounding the input stage decouplign cap at the input stage ground would be OK.

REmember, that same ripple was in the wires before, just had the cap on the other end of it than what we proposed.

The whole point is with multisection caps, the cap was never where the circuuit was, it was always off to the side somewhere.