I am restoring a 37-620 Philco and need advice regarding the cathode circuit of the 6A8 tube in the RF chassis. I purchased a set of service bulletins and schematics from Chuck and in reviewing the schematics, the earlier version bulletin #250 shows the cathode of the 6A8 connected to chassis ground. My 37-620 seems to be a second run with some updates but has the cathode grounded. A later service bulletin #251A has a 100 ohm, #21 and a .05 cap, #19 to ground. Should I install the later version or leave the grounded cathode? Many thanks for your help.
Your set may have been "monkeyed" with before you got it.
Go by the schematic that matches the CODE version of your chassis.
Code version will be on the blue and white paper label on the inside of the cabinet or ink-stamped on the chassis rear apron.
Chuck
Thanks for the info Chuck. I looked over the chassis and there is no code number. The only thing that I found was run #2, so I am going to follow your suggestion and use the 37-620 service bulletin 250. Many thanks for your help.
If you do no see a 37-620 Code xxx on the chassis or the blue and white paper tag glued to the inside of the case, then you have a Code 121, Run #2.
Merry Christmas,
Chuck