04-09-2020, 09:42 PM
1. Police band is working. I had to add a 1000pf cap across the compensator to get the low end in range. so now the high end and low end are close, but the center of the band is quite far off. The original coil was wound with 36 AWG. I didn't have any so I wound with 35 AWG. A question for you inductance guru's, how much difference would that make at these frequencies? If you think it would make the difference, I'll order some 36 AWG, disassemble the RF unit to get the oscillator coil out and rewind it again! However, one must wonder if the police band is worth the effort. I can now get the AM stations that are on the low end of the band, so... I have a similar tracking problem on the 4th band. Seems to me I've run into that before.
2. Problem solved. One of the WW controls was intermittently open, the other I smoked when trying to adjust the hum out. The reason it smoked is there was a short in that filament wiring to ground. So, when the pot reached that extreme, I was applying 6.3 volts through very low resistance. Two separate problems in the same 6B4 output tube filament circuits. The windings in the WW pots are copper, not nichrome, so I was able to bridge the breaks with solder. The pot is working and the hum is gone!
I have to redo the rubber coupler that connects the tuning cap to the tuning mechanism. and hook up the magnetic tuning lighting system. I'll also add my LED back light for the station dial. Then, tin plate the tube shields. The shields are missing from the RF unit since someone replaced the G tubes with metal tubes. I would like to replace those. See my ad in WTB.
2. Problem solved. One of the WW controls was intermittently open, the other I smoked when trying to adjust the hum out. The reason it smoked is there was a short in that filament wiring to ground. So, when the pot reached that extreme, I was applying 6.3 volts through very low resistance. Two separate problems in the same 6B4 output tube filament circuits. The windings in the WW pots are copper, not nichrome, so I was able to bridge the breaks with solder. The pot is working and the hum is gone!
I have to redo the rubber coupler that connects the tuning cap to the tuning mechanism. and hook up the magnetic tuning lighting system. I'll also add my LED back light for the station dial. Then, tin plate the tube shields. The shields are missing from the RF unit since someone replaced the G tubes with metal tubes. I would like to replace those. See my ad in WTB.
