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Philco 43B - IF Tube Shield Question - Printable Version

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Philco 43B - IF Tube Shield Question - davemc - 02-21-2007

I have attached a photo of my model 43B. The rear plate of the IF tube shield was bent slightly OUTWARD as received. I'm just curious if this is original, or if it was bent to make tube servicing easier. If anyone has a 43B and can comment, I would appreciate it. There is a curious curve in the shield plate near the chassis that suggests the bend may be original.

Sorry about the large photo.

[Image: http://mcclellans.com/Philco43Shield.jpg]

Thanks, Dave

- Chuck Schwark - 02-21-2007

Don't think it's original. It would not be necessary anyway due to the partitioning. Sufficient shielding. Someone obviously bent it to remove tubes. If it were original, it would be as high as the two-section cowl it's in front of and have the same dull grey appearance.

The two self-tapping sheet-metal screws holding it look too new as well.

- davemc - 02-22-2007

Thanks. I was hoping someone had a 43B in their collection in order to compare with. I guess the set is too rare (and even if there are other examples, they may not have this shield intact - but maybe the screw holes?)

I agree the screws are obviously wrong. But the plate looks to be original - stamped - smooth edges - not something someone cut with tin snips!

The thickness of the material and its color is the SAME AS THE REST OF THE SHIELD ASSEMBLY. In the photo it looks crooked - it is not - just bent at an angle.

Here's a photo of the back view. I agree that if it were original it would likely be HIGHER. But I cannot imaging someone adding this piece. In my experience, service people REMOVE AND DISCARD shielding - not install it. I suppose I will simply straighten it and install normal hex head self tapping screws until I get a definite answer.

[Image: http://mcclellans.com/Philco43Shield-2.jpg]

- davemc - 02-23-2007

UPDATE: Having finished the electrical restoration of the radio, I can definitely say one thing for sure: IT WON'T WORK WITHOUT THE SHIELD! The IF amplifier breaks into oscillation if peaked and the shield is not in place. This radio has no RF amp and gets all its gain in the 2 IF amp stages. The second stage runs wide open - no AVC is applied.

By the way, this is one hot radio. I think is works even better than the 16B (but of course, the audio is not as good).

So now I am leaning toward a field modification. Perhaps there was a later service note or a change that was not in the service pack I purchased. I don't think the original shield design worked that well. I cannot imagine why Philco did not simply use normal separate tube shields like were installed on the oscillator and 1st audio stages.

- davemc - 02-26-2007

Issue closed. Another chassis on eBay has the shield! Item 300083042702 So it is original. Looks like it is NOT bent backward like mine, which makes sense. Still looks like a production or field change though. And as stated before, the radio will not work without it in place. Also the retaining screw holes in the rear chassis are TAPPED and screws are 8-32 and not self-tapping. Weird!

- Chuck Schwark - 02-26-2007

Thanks for the info. Well worth noting! Icon_smile

Chuck