So where is the serial number located? Is it stamped into the chassis on the rear? I ask because if it is then my 70 does not match the schematics. The number stamped on this chassis is 795,569 which should have moved the volume control from the antenna coil to the input of the 1st AF detector. This one still has the control on the antenna coil.
Two stamps, top and back side on several of mine.
It's a dual volume pot, the 5k side feeds the antenna coil - the 250 ohm side feeds two 24 tube's cathodes.
Well I guess then the actual serial number for the later version must actually start with a letter. I looked right past the fact that this radio has the 4-24 tubes installed rather than the 1 in the later version. I picked this up in Kutztown last month as a working radio. Unfortunately the seller did not disclose that it was a semi-working radio. It picks up stations but the audio is badly distorted.
Jim,
Yes, according to the survey chart that was published in the ARC magazine (a couple decades ago now
) the serial numbers on the later 70 and 90 sets built after Dec 1931 started with A,B,and C respectively.