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 Post subject: How to go about replacing a feed through capacitor
PostPosted: May Mon 17, 2021 1:31 pm 
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Joined: Jul Mon 10, 2017 4:00 pm
Posts: 29
Location: Northwest, ohio
As per the attachment. I have a chassis mount capacitor with three wires coming out of it. Blue on the top of the schematic drawing. Red on the bottom. And the third goes to the chassis. The capacitor is marked 6+6 uf. This is a battery power silvertone model 1923. How do I go about replacing this type of cap? I have zero experience with feedthrough capacitors.
See circled capacitor


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 Post subject: Re: How to go about replacing a feed through capacitor
PostPosted: May Mon 17, 2021 2:04 pm 
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Joined: Jan Mon 16, 2012 4:15 pm
Posts: 8157
Location: Near Brandon, Iowa
First off, this isn't a feedthrough cap. It is an electrolytic cap contained in a metal box along with another electrolytic cap, with the assembly mounted to the top of the chassis.

You can either remove the box and gut it of its present contents, then restuff it with new electrolytic caps; or you can cut the wires going to it, leave the box in place, and install new caps on the underside of the chassis.

Note that the negative leads of the two new caps don't connect to the same place: C17 negative goes to chassis ground, whereas C23 positive goes to chassis ground.


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 Post subject: Re: How to go about replacing a feed through capacitor
PostPosted: May Mon 17, 2021 5:02 pm 
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Joined: Jan Tue 16, 2007 7:02 am
Posts: 4724
Location: Lexington, KY USA
here is the rest of the Rider schematic:
http://www.nostalgiaair.org/pagesbymode ... 016821.pdf

The parts list on this print shows C17 and C23 as a single unit. Three capacitors in one.

C23 does have the positive end connected to chassis ground.

Both sections labeled C17 have the negative end connected to the chassis, according to this print.

As already pointed out, you won't easily find new multiple capacitors like the original C17/C23. Just buy three single capacitors. The new ones are tiny, and most easily can be mounted under the chassis. It is usually nice to disconnect the wires of the old block and leave it, if it is mounted above the chassis. ( I do suggest that newcomers to radio work do this, rather than try to "re-stuff" the old one. Mistakes are much easier to find and correct if the new parts are not buried inside a box or can.)

Note that today you can most easily find 6.8, 8.2, or 10uF values. These will be fine to replace the C17 sections. A 150V rating is fine, as would be 160V, 250V or even 450V, but no need for the higher ratings.

So your connections for the replacements for C17 go:

Original "Third" (Black?) wire connects to the negative end of both new capacitors.
Original Red wire connects to the positive end of one of the new capacitors.
Original Blue wire connects to the positive end of the other new capacitor.

There is no need to use the old capacitors wires, except to show the points where the new ones connect. (Friction tape over connections made in the air is not considered good practice.)

Note that 25uF is also no longer a common value. 33uF is probably the thing to use for C23, though 22uF would be OK. 25, 35, 50, or 63V ratings will all be good for C23.

You do want to get the connections for these capacitors correct. One connected backwards will sap your B battery, and may even explode.

Ted


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 Post subject: Re: How to go about replacing a feed through capacitor
PostPosted: May Mon 17, 2021 5:25 pm 
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Joined: Jul Mon 10, 2017 4:00 pm
Posts: 29
Location: Northwest, ohio
Thanks for clearing that up for me. I guess the schematic drawing had me confused.


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