06-06-2013, 08:48 PM
I would not be too concerned about 40 uF as a capacitive input filter on an 80 tube. It is electrically the same as a 5y3 and many later radios used it with a 40 uF input cap. You will be changing the cap anyway so if you feel more comfortable, replace it with a 20 uF. The other cap after the field winding can be much larger with no extra peak loading of the rectifier. What it looks like is the power supply of a late 40's model.
Most of the caps in the metal box were used as decoupling filters for the two 27 audio stages which are now eliminated. The 6F5 is taking the place of the two 27's and bias is now provided for the 6F5 by what looks like a few thousand ohm cathode resistor. There is a plate resistor and a coupling cap to the grid of the 2A5. Looks pretty much as it should be done.
You may assume that the mods were done many years ago by the vintage of the parts added, and that the radio worked properly at that time. I would not be at all reluctant to retain the mods and at least try it with proper precautions.
Most of the caps in the metal box were used as decoupling filters for the two 27 audio stages which are now eliminated. The 6F5 is taking the place of the two 27's and bias is now provided for the 6F5 by what looks like a few thousand ohm cathode resistor. There is a plate resistor and a coupling cap to the grid of the 2A5. Looks pretty much as it should be done.
You may assume that the mods were done many years ago by the vintage of the parts added, and that the radio worked properly at that time. I would not be at all reluctant to retain the mods and at least try it with proper precautions.
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