Shaka Tube debug - Help needed....

[the_random_hero]

Oh, I see. You're really dividing the amps by volts, not multiplying them. I always wondered about that VA thing on transformers... 

Noope. V x A = VA
A = VA/V
V = VA/A

[Paul Marossy]

A = VA/V

Yeah, and that is what I said. You're dividing amps by volts to get that number.
6VA/12V=0.5A=500mA

[the_random_hero]

A = VA/V

Yeah, and that is what I said. You're dividing amps by volts to get that number.
6VA/12V=0.5A=500mA

Well, yes but no  That formula is diving volt-amps by volts to get amps.

[vin]

Lol. Gee Caps smell funny when they blow up!

I attached the power before swapping the caps around and one of them blew its top! 
At least now I know what was heating up the other day.

I've swapped the caps around now- no luck yet- I may have fried other components as well.

[Paul Marossy]

That formula is diving volt-amps by volts to get amps.

OK, I think I get it now. 

Gee Caps smell funny when they blow up!

Yeah, and the ones in a 50 watt amp not only smell really nasty, it makes a big gooey mess all over everything inside. 

[vin]

OK. Looks like its all systems go now.
The polarity of the cap coming from the diode to ground on the -Ve side in the schem seems to be incorrect.
I amended according to Arons posts:



-Ve is -9.6
+ve is 13.5

I assume the assymmetry is caused by the 2 different resistor values.

Thanks for your help folks.

[the_random_hero]

Are you sure about that? I was under the impression that no matter how big the voltage drop across the resistor is, there's no way it can swing the voltage to the second cap positive to ground.

[vin]

I'm saying the resistor value difference is what would be causing my -Ve and -Ve voltages to be different.

The cap polarity thing is in response to Aron's posts which were contrary to the original schem.
I'm still confused by this bc I assume people have followed the original with success. 

I'm assuming that people who know the ropes better than me would have glossed over this polarity detail and built it according to their general knowledge and experience.

[george]

I've built the shaka tube, I remember when Aron first put his schematic out it had the orientation of the 2 470uF caps connected to V- wrong, but it was quickly amended (after people reported caps blowing up!).

I've bult the amended one and it works fine - the bottom leftmost cap on your schemo is oriented incorrectly IMO.  Like it's neighbour, it should have + connected to ground.

[aron]

Although horrid, I think this one is correct:

[vin]

Yes I think you're probably right. I'm still getting fireworks.
I'll amend- and will repost on the original thread. It was obviously a typo on he redraw.

[george]

Although horrid, I think this one is correct:

That's the one! I still have a mangled printout of that one somewhere.