04-17-2019, 07:06 AM
Good morning,
I'm new to the Phorum but expect to visit often, hopefully more to improve my knowledge than plea for help.
I completed the electronic restoration of a model 87 and it plays wonderfully. The only thing that has me scratching my head are the grid voltages on the #26 RF tubes and the 45 output tubes. Rider's calls for 6 volts on the RF tube grids and 45 on the 45 tube grids. I believe they are all mislabeled as positive rather than negative voltages but that's not the issue. My issue is that I measure 0 volts on all the grids. I'm measuring from chassis ground. The plate voltages are within range of the schematic.
The radio performs perfectly so I don't think I have a problem but why am I not getting negative voltages at the grids? The only issue this radio had was an open field coil which I had rewound by the gentlemen at the Alabama Historical Radio Society. They do great work. Oh, it also had sprung tuning cables. That was a joy to fix. Finally decided to give up on the cables and use fishing leaders.
Thanks in advance for any help on my voltage conundrum.
Scott
I'm new to the Phorum but expect to visit often, hopefully more to improve my knowledge than plea for help.
I completed the electronic restoration of a model 87 and it plays wonderfully. The only thing that has me scratching my head are the grid voltages on the #26 RF tubes and the 45 output tubes. Rider's calls for 6 volts on the RF tube grids and 45 on the 45 tube grids. I believe they are all mislabeled as positive rather than negative voltages but that's not the issue. My issue is that I measure 0 volts on all the grids. I'm measuring from chassis ground. The plate voltages are within range of the schematic.
The radio performs perfectly so I don't think I have a problem but why am I not getting negative voltages at the grids? The only issue this radio had was an open field coil which I had rewound by the gentlemen at the Alabama Historical Radio Society. They do great work. Oh, it also had sprung tuning cables. That was a joy to fix. Finally decided to give up on the cables and use fishing leaders.
Thanks in advance for any help on my voltage conundrum.
Scott
