Philco RF cans to chassis connection - Printable Version
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+--- Thread: Philco RF cans to chassis connection (/showthread.php?tid=8410)
Philco RF cans to chassis connection - morzh - 01-08-2014
I have noticed that almost all of the cans in my 90 that shield the RF transformers, and that are flared after they pass through the chassis for the contact have poor connection which becomes better as I press on the can.
Pulling them out is out of the question. I of course can come up with some gasketing that would go undet that holder that holds the coil assembly inside it - it also bolts to the chassis.
But maybe someone already has devised a clever way to improve that connection.
RE: Philco RF cans to chassis connection - codefox1 - 01-08-2014
If the chassis and cans are steel, you can get a short length of wire and solder shield to chassis. Easily undone if this is not the problem
RE: Philco RF cans to chassis connection - morzh - 01-08-2014
No, unfortunately the cans in 20/70/90 are aluminum.
RE: Philco RF cans to chassis connection - LASJayhawk - 01-08-2014
Conductive epoxy? A dab on the underside of the chassis might work.
http://www.mgchemicals.com/products/adhesives/electrically-conductive/silver-conductive-epoxy-8331/
RE: Philco RF cans to chassis connection - BrendaAnnD - 01-08-2014
If there is enough room inside the can (pretty sure there is), you can use a short piece of solder wick or other braid, and blind rivet it to the inside of the can and use a ring connector under the coil mounting screw. If you use those ring connectors with the built in 'star washer' construction, you should have a good solid connection for many decades to come.
RE: Philco RF cans to chassis connection - morzh - 01-08-2014
What I need is a copper bar, placed between the coil holder and the chassis sing the flared can edge as a fulcrum. Times 4.
RE: Philco RF cans to chassis connection - jerryhawthorne - 01-08-2014
The way those cans are installed at the factory, hard to believe that is the problem. If loose which I doubt, try twisting them if you can to see if you can find a tighter spot. Those suckers were really put in there tight.
Regards, Jerry
RE: Philco RF cans to chassis connection - morzh - 01-08-2014
Jerry
It may not be a problem at all, but the fact remains, the resistance between the can and the chassis varies between 200 Ohm to 5 kOhm in one case.
And, they are VERY tighly compressed into the chassis. They are not loose. So - they do not twist at all. I believe an oxidation has developed between the can and the chassis.
RE: Philco RF cans to chassis connection - GarySP - 01-09-2014
Hello everyone. Just a thought... any auto parts store sells conductive paint for repairing the fine grids on rear window defrosters. Perhaps painting a heavy bead around the can to chassis joint after cleaning the area would cure your problem. Not that expensive, and worth a try. Take care, Gary
RE: Philco RF cans to chassis connection - morzh - 01-09-2014
Gary
Could be a way to do it. Thanks.
I also though that at work I have some EMI gaskets that is very conductive as it is a metal mesh and very elastic for compression, so a piece of it under the holder might just do the trick.
RE: Philco RF cans to chassis connection - morzh - 01-09-2014
I tried to twist them again.
Before I did I measured the resistance and in one can it was still 1k or so.
I aplieed the twisting effort to every one of the 6 cans, none really twisted or even snapped a little, but I think this effort was just enough to break the aluminum oxide or whatever it is that formed in between the cans and the chassis. After the re-measurement I can see that the resistance of each can is between 0.25 to 0.4 Ohm (0.2 is the meter's leads resistance).
Now not that it affected the performance - no, I do not think it did, but at least now when I touch a can, I hear a reduction in volume no matter which can I touch. Before some cans I touch would increase the volume and others would decrease it - this was what prompted me to check the grounding.
Well, it is not that important but I like things in order and functioning as intended to the best of my knowledge and ability, and not the way they want to function, which is usually "leave us alone - we do not want to work at all".
PS. I will probably still get some of that EMI gasketing, just to make it reliable.