previous: Mook I seem to have gotten the bias supp... -- 8/19/1999 11:10 PM

Re: AAAAHHHH!!! Could I have FRIED my PT???

8/20/1999 3:04 AM

Graywater

Re: AAAAHHHH!!! Could I have FRIED my PT??? Mook,         Like Moocow said, unhook the yellow c.t. from ground, now!!!     The c.t. is meant to be your B+ feed - in a non c.t rectifier circuit the 5v heater voltage "rides" on the DC output as 60 Hz ripple. Using the c.t., 2.5v to each heater pin with 180 degrees phase relationship, you eliminate ("buck" out) the 5 volt, 60 cycle ripple.         Effectively, you have been passing all of the B+ current, through the filament winding, to ground - not quite a dead short but close enough. I dunno, but I'd probably disgard the 5Y3 that suffered this abuse or reinstall it after you've rewired the circuit (and watch it carefully under full load for at least 10 minutes).             When you're installing a tranny, it never hurts to run over the connections with an ohmmeter before soldering - gives you time to think about the circuit. By now you know, but just to remind, heater circuits in directly heated rectifiers must be kept off ground - this is the source of your rectified B+. Even with filament rectifiers, it is sometimes better to provide a separate heater winding on the PT to prevent frying heaters in the other tubes should you get a heater-to-cathode short in the rectifier.         GW

 

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jmartin If you can pull 150ma plus from tha... -- 8/20/1999 3:03 PM