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Brent(Tina)
ke1gf wrote:B-TINA, I took a look at your pictures and I see that you've got the grounds of your input transformers connected to the heatsink with long leads and not to your source bus...
This is a bad idea, the grounds should be soldered directly to the source bus so that the transfomer is directly connected between the FET's sources and the Gates....
Once other thing, I believe that you wound your input transformers with 4 turns on the primarys, this is the way that I initially did mine, But I changed to 6:1 turns ratio with outstanding results. When I was running 4:1 my twisted pair would get hot and the modules were a pain in the butt to balence.
Sincerely
-Bill 'GF
ke1gf wrote:Tina... I've been following your pictures, keep up the good work!
Another idea that has crossed my mind. The filter that you've built has a first inductor value that will only give you maybe 100% +- 10% modulation percentage if correctly loaded... You'll notice that your positive peaks will flat-top. When you get rig up and running you might consider pulling a turn or two off of the first inductor But watch for negative peak crapout. It's a tradeoff between negative/positive peak attainability. This is one of the shortcommings of this particular implimentation of PDM.
-Bill 'GF
frank carcia wrote:Brent,
I notice you only have 2 screws on your source busses. The coating on the heat sink is an insulator so this places a huge inductance in your source circuit. I suggest you drill and tap a hole near each source lead to eliminate this loop. fc
Brent wrote:
Did you change that value on the first inductor?
ke1gf wrote:Brent wrote:
Did you change that value on the first inductor?
which value is that Tina?
I counted your turns
-Bill 'GF
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