[davemc]

Does anyone know if the 6A8G converter tube in the 40-216 had a tube shield? The tube placement diagram in Riders indicates no shield. However, in my set a 6A8 metal tube was installed, and there is an indication on the top of the chassis that a shield base was once there. There is a clear outline around the 6A8G socket of a shield base - but the rivets are not torn out, or even visibly damaged.

My guess is that a "repairman" ripped off the shield base in order to install a metal 6A8 to replace the original 6A8G.

IIRC Philco did not use metal, and possibly not even GT types in 1940.

I just feel that the 6A8G would have a shield.

Thanks

[49Stude63]

Dave on any Philco set that I have the 6A8 is shielded, nomally the only ones Philco did not shield would be the rectifier tube, the output tubes, or tubes in the output circuit. Any tube in the RF, IF or Osc usually have a shield unless they are metal and Philco did not use metal tubes that I can recall. The base of the metal tube is too big to fit in the shield base so if a metal tube was installed the tube base was either cut and hacked or removed.

[Ron Ramirez]

According to the Philco Service Bulletin for this set (same tube placement diagram as in Rider's), there originally was no shield on the 6A8G.

Actually, on a lot of Philco models, the det-osc tube had no shield, while RF and IF tubes are almost always shielded.

And, no, Philco never used metal tubes originally in their radio receivers.

Your radio should work fine with no shield on the 6A8G.

[49Stude63]

I was basing my comment about the shield on the models which I have mostly the magnetic tuning models and typically those used the 6A8G (shielded) and located on the sub-chassis. I think the function on the magnetic tuning models was also det/osc. And on other 37 non-magnetic tuning models 37-2670 (it is labled 6A8EG (but I think the EG was a suffix for being an export model, the 6K7 also has the EG suffix on the tube label. I wonder when Philco switched from shielding the 6A8 in the 37/38 models to not shield them universally?

[davemc]

Thanks guys. FYI, here is a photo of the existing 6A8 socket area on the radio.

[Image: http://mcclellans.com/6A8.jpg]

I can't tell if a shield base was there, or perhaps just a shield was installed on a 6A8G tube without the shield base, or maybe a shield base was removed during the manufacturing process.

The rivets look different from the others in the set - more flat.

Thanks again,
Dave
[/img]

[49Stude63]

I don't have the same model but I seriously doubt there would be an outline if the shield base was not installed during the manufacturing process. Also the tube socket does not appear to be original as you mentioned. I know and I checked my 37/38 models and they do have the 6A8 shielded.

[davemc]

The socket is obviously a different color than the rest in the radio. Also, there is a corner clipped off that aligns with the small indentation seen at about the 1:30 position. But the wiring on the socket looks undisturbed and original. Also, the socket is missing pin 1 (typical for sets that are designed for G type tubes).

And the rivets on the bottom look like all the rest in the radio. I would think that if a technician replaced a socket he would use SCREWS, not rivets. I cannot imagine installing rivets on this large and heavy chassis once components and wiring were installed.

Just a trivial mystery! As Ron said, I'm sure the set will work fine without a shield, as there are sets out there without shields. Perhaps the shield base was removed and socket changed(?) on a stock chassis by Philco before the set was populated and wired. Production change?

Dave