The PHILCO Phorum

Hi all,
I have a question someone may know the rhyme or reason behind this. On some of the Philco tabletop sets I've seen, there is a decorative design foil board under the chassis. No, it's not asbestos, but a foil covered piece of thin cardboard.

The last 2 model 84 and 84B had this foil. Other models may have the same, I can't remember.
The foil was probably used to dissipate or insulate heat from getting to the cabinet. That is obvious. But, the actual material used. Was it that Philco got a special deal on some kind if foil boards that were used for something else? They may have then cut them to size, punched holes etc. I can't remember seeing these type of designs on anything else from that era.

If that's the case, i wonder what kind of use they had, other then being used in a radio? I suspect that Philco didn't take the time and effort to design an embossed pattern, just to go under a chassis. There has to be some other reason. Or, maybe not. It's one of those things an inquiring mind wants to know

Here are the last 2 sets I saw the foil on.
Any other speculation about the foil ?
Thanks.

I have no idea, Gary...

Is it situated with the foil side up to make contact with the chassis? Since it is in the model 84 maybe it's to help electrically shield the bottom of the chassis to reduce any emissions from the regenerative detector?

It could be use to reduce hum as the regenerate detector operates at a very high gain. If you put your hand near the 77 tube you will notice an increase in hum. Good grounding around the detector/wiring is a must.
Terry
ps the radiation from would be a 460kc not at the frequency that the set is tune to. That was the problem back in the 1920's as the detector was tuned to the station on the bc band and would radiate over the broadcast signal to nearby receivers.

I think Gary is asking why the foil has decorative embossing.

I don't own an 84, and it's been a while since I had one here. So I honestly do not remember if any of the 84 sets that have passed through here had embossed foil, or not. I guess I never paid attention to it before.

Thanks guys,
I do understand about the foil as heat shelding or RF sheils, but the decoration seemed too ornate for just a sheld. Like they were made for something else originally.
They do look neat. Maybe Chuck has seen these.
Ron, I figured of anyone would know it would be you
Take care,
Gary.

Gary

In all of the research I have done on Philco, never have I found anything mentioning decorative foil. :

You showed two different patterns. Just a guess here (and all I can do at this point is guess)...maybe they got a good deal on embossed foil, that was intended for some other purpose, from some other company? It wouldn't surprise me, given Skinner's "thrifty and Scotch" reputation.

They both look reminiscent of crystal growth patterns to me. Could it be some sort of vacuum deposited aluminum coating? Or a transparent coating over top of the aluminum?

The foil may have been added by a previous owner, as a shield or maybe even a kind of counterpoise or artificial ground. Every so often I get a radio that has some interesting or even ingenious additions made by previous owners. A Silvertone I got quite awhile ago had an internal antenna AND an internal rectifier eliminator. It's reception is excellent and it plays without the 84 tube. I have a Philco 623 at my parents home and a Philco 34 here, both of which had battery eliminators added by previous owners. Both play well. I am sure that we all have gotten radios that have older repair attempts, some successful, some not so much..... Personally, some of the biggest challenges I have had trying to get a radio to work have come from correcting old "repairs."

Conuctive foil is still being used, as a cheap alternative to a bottom chassis plate. I recently worked on a pretty new guitar amp, and it had foil where the bottom plate should have been, and the glue failed (you know the guitar amps have everything upside down,) so it was a real mess. Dead short output tube, bad diode, etc...

Thought about making a bottom with a piece of discarded
computer housing, but decided to just re-glue the original foil to the cabinet, and make sure the wiper was making contact. Been 4 months. Assumed working OK.,

HI guys,
We all know the purpose of a foil bottom, used as a shield. My curiosity was why patterns, and thought these foils were used elsewhere in industry.

I think Ron's explanation works the best, that's what I was thinking. If the company found a cheap source for foil they would use it despite having a pattern on it.
I am just thinking what original use would the foil be? Placemat pieces? Maybe inserts for a gift box? Who knows? One of these days I'll see something with the same pattern on it from back in the day.

The two examples shown are factory issue pieces. They came from 2 seperate radios bought several years apart. Model 84 early and the later 84B.

Curiosity got the best of me, so I went down and removed the chassis from a future restore 37-84. The foil pattern was again differnet. Not in good shape, but this is a third pattern.

Audin, this throws out the crystal growth design theory There is nothing on the foil. If I pressed it down it would be flat.
Here's the latest, kind of cool woven efect.




So, the mystery continues. I just thought it would be an interesting thing to try and find out about.
Take care guys.
Gary.

Now that I've seen your latest photos, Gary, I think I used to own an 84 that had a pattern in the foil like the one in your last two photos.

But it's been a few years or more since I owned an 84, and I do not own one now, as mentioned earlier.

Next time I acquire one, I'll be paying attention to this, for certain.

Thanks Ron,
That last pattern was really cool. I'd like to see the machine it was made on. With this being on the net, someone may come in months later and fill us in on it. Hopefully