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

 :

8/20/1999 12:33 PM
Mook	Re: AAAAHHHH!!! Could I have FRIED my PT??? Yes! This was it. I was able to run it for about     10 minutes with no adverse effects.         I did "fry" 3 rectifiers in the process, one being     a NOS RCA.         I blame Hammond for this because their wiring     diagram shows a ground connection for the CT.         Thanks everyone.         Mook

 

8/20/1999 3:04 AM

Graywater

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

 

8/20/1999 3:03 PM
jmartin	If you can pull 150ma plus from that trans. Its time to move up from that 125Ma 5Y3 to a 5V4 or 5AR4.         JM

 

<<First Page

<Prev

Page 2 of 2