Hi Craig,
Only the secondary carries the full current. So for a 6.3 A load you could easily get by with an 8 ~ 10 A secondary. Given the intermittent nature of your current demands a 6 A secondary may be fine. EI core.
So use a 25 volt transformer. Center tap may give you more flexibilty if you move, but it doesn't do anything else for you.
Wire the secondary in series with the load (your amp's AC supply). Try a lamp and measure with a meter. The primary goes across the line (like you normally would). If you end up with a higher voltage just reverse the connections on the primary to change the phase. The measured voltage should now be lower by a bit more than the full load rating of your 25 V transformer.
I guess a 30 W loss with a 1KW transformer is normal for those.
Hi Stocker,
Craig is using a fixed tap type transformer to the best of my knowledge. Not a variable AC transformer (variac). Wouldn't be the first time I've been wrong though!
-Chris
Only the secondary carries the full current. So for a 6.3 A load you could easily get by with an 8 ~ 10 A secondary. Given the intermittent nature of your current demands a 6 A secondary may be fine. EI core.
So use a 25 volt transformer. Center tap may give you more flexibilty if you move, but it doesn't do anything else for you.
Wire the secondary in series with the load (your amp's AC supply). Try a lamp and measure with a meter. The primary goes across the line (like you normally would). If you end up with a higher voltage just reverse the connections on the primary to change the phase. The measured voltage should now be lower by a bit more than the full load rating of your 25 V transformer.
I guess a 30 W loss with a 1KW transformer is normal for those.
Hi Stocker,
Craig is using a fixed tap type transformer to the best of my knowledge. Not a variable AC transformer (variac). Wouldn't be the first time I've been wrong though!
-Chris
Thanks fo clarifying Stocker now i see what you mean 
.
I dont think its oscillating as the output is clean under a scope and the amp itself remains quite cool during operation.
Anatech is right though i am not using a variac, just the primary of a large transformer.
I will pick up a 25v EI core traffo as soon as i can get one cheap to give this a try.
Thanks all
Craig
.I dont think its oscillating as the output is clean under a scope and the amp itself remains quite cool during operation.
Anatech is right though i am not using a variac
, just the primary of a large transformer.I will pick up a 25v EI core traffo as soon as i can get one cheap to give this a try.
Thanks all
Craig
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