Feed Throughs

[KA8WTK]

Hello,
  The Heathkit SB-110A I am working on uses a .001/1kv feed through to pass high voltage into the final cage. This feed through looks like it has been over heated at one time and seems "loose" inside. I am not of a mind to trust it. I have looked at the major parts houses for another (Mouser, Newark, Digikey, RF Parts) and can't seem to find any. Ebay is not helpful either.
  My thoughts are to replace the feed through with a regular ceramic feed through and put a cap from it to ground inside the cage (requires drilling). Or, I have a feed through that looks more like it belongs on a piece of test equipment that is the right diameter to fit but would also need the cap added. The problem with this is I don't know the rating for the feed through.
  Any other ideas out there before I start drilling?

Thanks,
              Bill KA8WTK

[WD8BIL]

Can you take a pic or 2 to give an idea of size, Bill?

Is there room inside the cage for a 2 lug terminal strip? Maybe feed the wire through a grommet to the strip and put the cap in there?

[WBear2GCR]

You might just take the ceramic part out.

Then using either Teflon insulated wire or solid wire and a Teflon
sleeve (you could strip insulation from wire) affix that in the old
metal part with silicone rubber. Just make sure there are no air gaps.

It is possible to simply measure the capacitance of such a thing, but it will be
lower than the original. Won't arc over. Probably really isn't essential, the capacitance, I
would guess.

They sell "flowable" silicone rubber at the auto parts store for windshields, clear.
It will flow in like a very viscous liquid before it sets. Ideal.

Otoh, old school ceramic feedthoughs are sold on Epay and by that infamous midwest
surplus dealer, and probably Fair Radio too... and at hamfests, and as part of other
more or less parts chassis...

                       _-_-

[WBear2GCR]

Can you take a pic or 2 to give an idea of size, Bill?

Is there room inside the cage for a 2 lug terminal strip? Maybe feed the wire through a grommet to the strip and put the cap in there?

Once the RF is "in" the RF is in...?

[Detroit47]

Bill

I have aa bunch of feed through can you provide a picture? How volts are on the line? I would be happy to send you one if I have it.

John N8QPC

[KA8WTK]

  Thanks for the ideas! They pretty much add up to what I thought I would do. The smallest ceramic I have would not fit between the blocking cap and another door knob cap. I have some Nylon and some Teflon and I was thinking of making a feed through on the lathe that would fit the space. I have some wire with Teflon insulation. I have 1kv caps. Sounds like every thing I need. Let's pull it out.
  This is one of those things where you have to remove 6 things to get to what you want to remove. All the stuff in the way makes it hard to see what is really going on, but the feed through looked burnt. Once I got it out, I discovered the burnt "stuff" was what was left of some clear plastic tubing that was placed on the HV wire and slipped onto the feed through. (There is a step in the manual where this is done.) Somewhere along the line, probably when the SB-500 2 meter transverter wiring was added, some of the tubing was was left on the feed through and when the second HV wire was soldered on the tubing became a crispy critter. Got rid of the burnt stuff and the feed through looks really good so I am going to re-use it.
  I appreciate the ideas and the offer of another feed through.

Thanks,
             Bill KA8WTK

[W3AGD]

There are a few listed (with pics) on www.surplussales.com

Frank S.
W3AGD