12-30-2018, 05:31 PM
Hello all.
I'm trying to bring a customer's 37-84 back to life. (schematic attached) Originally it had the typical hum and would tune no stations. After a complete recap the hum is much reduced, but still no RF what so ever. The radio itself is in very good condition with no work performed on the chassis. I have: replaced all caps, out of spec resistors, checked all tubes, extensively checked continuities with no luck. All voltages are dead on. Resistance and voltage across the FC is perfect. I have tried applying the antenna to 77 tube grids with no effect. I'm stuck !!!!
There is one section that does seem odd to me. There is a parallel capactor and resistor (6, and 7) I would assume there to create bias for the 77 tube. However, there is no voltage of any kind across them. Nothing , nada, zip. This doesn't seem normal.
Unfortunately, my signal generator shot craps so I am awaiting a new one. Any suggestion where I might look next in the mean time. I do have replacement 77 and 42 tubes on the way and I'll give that a try.
Thanks Steve
I'm trying to bring a customer's 37-84 back to life. (schematic attached) Originally it had the typical hum and would tune no stations. After a complete recap the hum is much reduced, but still no RF what so ever. The radio itself is in very good condition with no work performed on the chassis. I have: replaced all caps, out of spec resistors, checked all tubes, extensively checked continuities with no luck. All voltages are dead on. Resistance and voltage across the FC is perfect. I have tried applying the antenna to 77 tube grids with no effect. I'm stuck !!!!
There is one section that does seem odd to me. There is a parallel capactor and resistor (6, and 7) I would assume there to create bias for the 77 tube. However, there is no voltage of any kind across them. Nothing , nada, zip. This doesn't seem normal.
Unfortunately, my signal generator shot craps so I am awaiting a new one. Any suggestion where I might look next in the mean time. I do have replacement 77 and 42 tubes on the way and I'll give that a try.
Thanks Steve
