01-25-2009, 01:30 AM
A good friend wants me to restore his childhood era family 1959 Zenith mod G 730 ( chassis 7C05). I dont have a schematic, but really dont need one, as these are fairly straight ahead circuits. I have it fully recapped & working again on both AM & FM. Getting low voltages from the old orig selenium rectifier. Its been quiet awhile since I had to replace a old selenium rectifier with a diode/ resistor sub. Seems if I remember correctly, I used a 1N-4007 type diode with a 50 ohm 5w wirewound resistor in series last time I had to replace one to get the voltage back up? This is a old half-wave rectifier with "paint-bubbling" on the plates.Its needs changing. This circuit is a ac/dc type 7-tuber ( all miniature tubes, usual compliment for AM/FM receivers of that era). One side on the ac cord connects to pin # 3 of the 35C5 audio tube, runs to the (-) negative side of the old selenium rect with a old bumblebee cap to chassis grnd. I figure a .01/600 will work there. The (+) side of selenium rect feeds a 22 ohm 1-watt carbon then to one side (40uf/160v) section of the B+.
I have all the parts here if the 1n4007 works for this, and if I remember correctly, I can remove the old selenium assy, mount a terminal-strip in its place, add the (-) side of ac line to one end of the 50 ohm resistor, soldered in series to the negative end of a 1N4007, then + side of diode to the 22 ohm that feeds the B+. Does this sound correct? Thanks in advance for refreshing my memory!I can bring the set up slow with my variac & check filament voltages after I swap out the parts & see if the tubes are operating at normal current ratings. Any suggestions would be appreciated!! Im getting absent minded in my older age!! Randal
I have all the parts here if the 1n4007 works for this, and if I remember correctly, I can remove the old selenium assy, mount a terminal-strip in its place, add the (-) side of ac line to one end of the 50 ohm resistor, soldered in series to the negative end of a 1N4007, then + side of diode to the 22 ohm that feeds the B+. Does this sound correct? Thanks in advance for refreshing my memory!I can bring the set up slow with my variac & check filament voltages after I swap out the parts & see if the tubes are operating at normal current ratings. Any suggestions would be appreciated!! Im getting absent minded in my older age!! Randal