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Re: No CT on PT, how to lower B+ ????

1/18/2004 8:15 PM
ted m Re: No CT on PT, how to lower B+ ????
Try putting together a box with a couple of levitron wall outlets in series (if you buy the duals, plug one up on each with those safety plastic deals. put a 300W bulb in one (or get Y adapter and two 150W bulbs, or a 200W + 100W, etc.), and your amp plug in the other.  
Check your heater voltages, make sure they're not dropping more than ~10%, your plate voltages should be nicely dropped.
1/18/2004 10:52 PM
Ian Anderson

Levitron wall outlets? - are we talking lightbulbs here? If so, this amp is a touring amp and doesn't get the kid gloves treatment, so I think lightbulbs to drop the voltage down is not a rugged enough solution. Cheers anyway - I'll go with the zeners.  
... Ian :)
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1/19/2004 5:55 AM
ted m
heavy duty (garage door light bulbs, outdoor type bulbs) from GE and Sylvania can be quite rugged.
1/19/2004 7:28 AM
Ian Anderson

"heavy duty (garage door light bulbs, outdoor type bulbs) from GE and Sylvania can be quite rugged "
yeah but you know what I mean - lightbulbs=bulky & fragile, zeners=small & tough.  
I'll post results when I get through with this.  
Cheers... Ian :)
1/19/2004 11:11 AM
Steve Conner

Ian, it looks like those zeners would be fine for seriesing if you were using them as screen droppers. The power dissipation won't be that great. If you were using them to drop the plate voltage they most definitely would need heatsunk.  
You can actually buy insulating kits that let you isolate those studmount diodes from the heatsink. Try RS, Farnell, etc. Or just use a little heatsink for each diode and screw the heatsinks onto some kind of plastic insulator support.  
P.S. A Levitron outlet sounds like what you would plug your Lifter into :D
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