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Transformer Boost/Buck Connections

5/15/2000 10:51 PM
CG	Transformer Boost/Buck Connections Hi guys, I'm hoping someone can explain to me how current is shared in boost and buck connections. I'm a beginner, so any level of info is welcome! I guess I should say why I want to know first: I'd like to use a power transformer I have sitting on a shelf in a new amp. Unfortunately the transformer plate winding has a higher voltage than I need AND is rated for less current then I'd like. Sounds like an unusable match at first, but if there's any way I can work it out it would save me the cost of a new PT. A choke input filter should drop the B+ to almost the right area and I hear this type of circuit heats the transformer less than a capacitor input. I don't know how much more current can be safely drawn though. I guess I'll end up experimenting with gradually greater loads and closely watching the transformer for heating. Any ideas for measuring transformer temperature? Is surface temp okay? It's also said that leaving other windings unloaded will increase the amount of current you can safely draw from the plate winding. So my question is, what happens with the current in boost or buck connections? In my case I could use the 5V rectifier winding to buck the B+ down a bit more. There are circuits in Kevin O'Connor's books for doing this, but I couldn't understand if they actually drew any current from the new winding. That 5V winding has quite a high current rating compared to what I need, so if I could some how add it to the plate supply, would that solve my problem? Sounds too good to be true, so I'm probably missing some basic. (I could use the 6.3v heater winding too, since I have a 12.6V transformer sitting on the same shelf of rescued parts) Any ideas appreciated. I know I'm the one with the darn transformer and I should go and try it out myself, but some background understanding is always reassuring. -cg

5/15/2000 10:51 PM

Transformer Boost/Buck Connections

Hi guys, I'm hoping someone can explain to me how current is shared in boost and buck connections. I'm a beginner, so any level of info is welcome! I guess I should say why I want to know first:

I'd like to use a power transformer I have sitting on a shelf in a new amp. Unfortunately the transformer plate winding has a higher voltage than I need AND is rated for less current then I'd like. Sounds like an unusable match at first, but if there's any way I can work it out it would save me the cost of a new PT.

A choke input filter should drop the B+ to almost the right area and I hear this type of circuit heats the transformer less than a capacitor input. I don't know how much more current can be safely drawn though. I guess I'll end up experimenting with gradually greater loads and closely watching the transformer for heating. Any ideas for measuring transformer temperature? Is surface temp okay?

It's also said that leaving other windings unloaded will increase the amount of current you can safely draw from the plate winding. So my question is, what happens with the current in boost or buck connections? In my case I could use the 5V rectifier winding to buck the B+ down a bit more. There are circuits in Kevin O'Connor's books for doing this, but I couldn't understand if they actually drew any current from the new winding. That 5V winding has quite a high current rating compared to what I need, so if I could some how add it to the plate supply, would that solve my problem? Sounds too good to be true, so I'm probably missing some basic. (I could use the 6.3v heater winding too, since I have a 12.6V transformer sitting on the same shelf of rescued parts)

Any ideas appreciated. I know I'm the one with the darn transformer and I should go and try it out myself, but some background understanding is always reassuring.

-cg

Replies:

mark durham cg, If you want to lower y... -- 5/16/2000 9:53 PM
Randy Have you considered adding a zener ... -- 5/17/2000 10:28 AM