06-22-2007, 11:07 PM
Hi Frederic
In reading your post, it made me start thinking...and so I decided to look up the schematic for Model 645. It seems to me that your set is similar to, but not exactly like, Model 645.
Model 645's Type 78 RF tube, Type 6A7 det-osc tube, and Type 78 IF tube have all of their cathodes tied direct to ground as you describe.
The resistor you refer to was often called a "B-C" resistor by Philco. A more correct term would be a bias resistor. Anyway, this resistor differs in the 645 from that used in Model 640 - but is not the same resistance as you describe.
Could be that your radio is a late production 640; and in addition, perhaps some undocumented changes were made for the French market? It is quite normal for Philco to have made running changes in production, sometimes without bothering to take the time to document those changes. This makes things somewhat frustrating for us now, seventy-one years on, but for the true Philco Phanatic, it just makes life more interesting.
In reading your post, it made me start thinking...and so I decided to look up the schematic for Model 645. It seems to me that your set is similar to, but not exactly like, Model 645.
Model 645's Type 78 RF tube, Type 6A7 det-osc tube, and Type 78 IF tube have all of their cathodes tied direct to ground as you describe.
The resistor you refer to was often called a "B-C" resistor by Philco. A more correct term would be a bias resistor. Anyway, this resistor differs in the 645 from that used in Model 640 - but is not the same resistance as you describe.
Could be that your radio is a late production 640; and in addition, perhaps some undocumented changes were made for the French market? It is quite normal for Philco to have made running changes in production, sometimes without bothering to take the time to document those changes. This makes things somewhat frustrating for us now, seventy-one years on, but for the true Philco Phanatic, it just makes life more interesting.
--
Ron Ramirez
Ferdinand IN
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