Re: Zener Diodes in a 5F1 Champ to lower B+?

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1/19/2005 9:45 PM
Bruce /Mission Amps	Re: Zener Diodes in a 5F1 Champ to lower B+? What PT and rectifier are you using?   If 5w-10w zeners are hard to come by,...   Since this is a class A amp and the PT is under a more constant load, you can use 3-5w 150-220ohm dropping resistors in the high voltage secondary leads to the rectifier, lowering the actual AC before it is rectified.     Bruce

 

1/20/2005 6:31 AM
marT	Hello Bruce, it is champ PT from shinrock, rectifier is a Phillips 5Y3WGTA.     What formula would be needed if I were to theoretically calculate the correct resistor value? I guess I would need the PT specs first and then basically Ohm's law or is it more complicated? Thanx for your tip!

 

1/20/2005 3:27 AM
Dave H.	1N53 series

 

1/20/2005 6:34 AM
marT	dave, thanx for the link, I saw those, but was looking for a way to drop a large amount of voltage and didn't want to clutter up the inside of the champ with all those zeners But anyways, I was in contact with Chris who already sent me some zeners, I should have them next week, will report back!

 

1/20/2005 7:10 AM

Dave H.

In my 18W amp I use 7 x 10V 5W zeners for a low power option. I mounted them on a tag board. They run at less than 1W each so they don’t get too hot. In a Champ you could use a resistor to drop 50V. Put it in series with the B+ from the first filter cap and add a second filter cap after the resistor to form a pi filter. This will reduce the B+ voltage and the hum which can be a problem in a single ended amp. The 5C1 Champ circuit is like that. A 1k/1k5 10/15W resistor should drop about 50V.     Dave

 

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