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Hello. I'm fixing up a Harvey Wells T-90 transmitter and have a
question. Perhaps another T-90 owner would be so kind as to help. The tube socket resistance table in the instruction manual states that the resistance from V9 pin 8 to ground should be 400 ohms. Same for V10 pin 8 to ground. These are the grids of the modulator tubes, fed in push-pull from the secondary of driver transformer T1 which has a center tap to ground. In my unit, the resistances are only half that much (211 ohms and 223 ohms). I'm suspicious that the 400 ohm value in the resistance table might have been meant to pertain to the *total* resistance between the two grids. It would seem an unlikely coincidence for the transformer to have failed with shorted turns and end up with exactly half the specified resistance in both halves of the secondary. Of course, that's always a possibility. Would someone else with a T-90 please help by checking these resistances for me? I would appreciate it very much. (Disconnect the transmitter from the power supply while making this measurement.) 73 & TIA, Joe K9LY |
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