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previous: Steve A. Carlo:  &... -- 9/9/2000 2:37 AM

Re: AC-30 PT? Now I'm Confused.....

9/9/2000 6:04 AM

Carlo

Re: AC-30 PT? Now I'm Confused..... Hey Steve -     quote: "I had heard that the AC30's use/need a low voltage/high current PT to work right with the quasi-Class A output section. I guess the 200mA rating should be okay- right?"     i believe 200mA is plenty. It works for me...YMMV. FWIW, I know at least 3 of my amps built with said tranny that have been in relatively heavy usage (3-5 nights/week) for over a year with no problems. Bear in mind, these amps are all running the plates around 350-360VDC, which is rather high. Then again, a year isn't very long in the life of an amp...time will tell. As for voltage, the number i've heard most often as the correct value is a plate voltage of 320. You may want to check out the following schematic. it's for a 1964 AC30. It has all the tranny numbers...OT @ 4k and the PT 280-0-280 @ 160mA. Be warned the schem is rather large.     http://members.aol.com:/funkyloon/ac30.html     quote: "Do you see any problems with adding a few 10V/5W zeners to the PT CT circuit to drop the B+ voltage maybe 20 or 30 volts? Mouser sells the #610-1N5346B zener (9.1v/5w) for 52 cents apiece and they are much easier to use than the heavy-duty 50 watt stud mount ones, especially if you are not exactly sure how much you want to drop the B+ voltage!"     Sounds reasonable to me...i seem to recall Bruce mentioning this before, (stringing smaller/cheaper zeners together to get a safe wattage) but i have no experience with using zeners to drop voltage. IOW, you better ask someone who knows. ;o)     If it were me, since the Hammond PT is designed for a 115VAC, i would use the transformer boost/buck method outlined on RG's page.     Carlo

 

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Pete I'v always been a bit mystified abo... -- 9/13/2000 10:50 PM