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I don't think it was a prime consideration because they didn't need that much current to drive all the tubes I wish to drive now. Could I hurt it by paralleling the windings? I sure wouldn't think so.

I would like to add a 6.3V transformer just for the 6SN7s, but I just won't have the room after my capacitor bank, I'm pretty sure.

Kyle

The Dynaco design allowed for the additional current draw of 1A per side when using the Dynaco preamp. When you figure the 7199's draw .45A EA that gives the capability of 1.45 A per side. when you deduct 1.2A for one side and .6A for the other side you are still in the game. The dynaco was designed to allow for a current draw of 3.45 per side NOT counting the current draw of 1A per side for the preamp.

Do the math...2) EL34's or 2 6CA7's draw 1.5 A EA.
2) 6SN7's draw 1.2 A total is 4.2A

other side 2) EL34's or 2) 6CA7's draw 1.5A EA
1) 6SN7 draws .6A 3.6A

I don't see the problem and or need to either parallel up the 6.3 winding or add another transformer.
I don't consider the parallel operation of the 6.3 V filament as a good idea because I don't believe in paralleling transformer winding due to the fact that they cannot be relied upon to deliver mirror performance.

The prototype I have over at Planet10's place right now with a stock PA-060 has been running for months with the load of:

4 x EL34
2 x 12BH7
2 x 6CG7
1 x 5751

(SS rect)

And it isn't dead yet :-)

Cheers!

Alright, good to hear. Geek, if I calculated that right, all of those tubes are drawing 8.75A!! Holy cow! I'm surprised that transformer is still living!

Have you cooked an egg on that transformer yet? :-)

Kyle

quote:
Alright, good to hear. Geek, if I calculated that right, all of those tubes are drawing 8.75A!! Holy cow! I'm surprised that transformer is still living!

Why are you so surprised????

The transformer is capable of 8.9A

It really seems to be pushing it! At startup, it's a lot more than 8.9A!! Not for very long, albeit, but still!

Kyle

By the way, I've ordered a new chassis, screws and nuts, a bunch of resistors, and some capacitors. I decided to go with 100µF 350V caps.

Is there any benefit having one capacitor larger than the others in the power supply?

Kyle

Hi Kyle,

If the tube rect was in there, it would be stressed. In practise, you can draw a tad more from heavy (filament) windings if the transformer core VA rating isn't stressed ;-)

Cheers!

quote:
It really seems to be pushing it! At startup, it's a lot more than 8.9A!! Not for very long, albeit, but still!

Its the paranoid thinking that helps sell the upgrade power transformer.
I ran my Dynaco that had the Blackburn 6SN7 board for hundreds of hours in 90 degree heat without a melt down. Just pointing out the engineers designed the transformer with the 8.9A load in mind. They also took into consideration the startup did take an additional amount.

I guess the uninformed here know a hell of a lot more than the engineers that designed the transformer.

Well, as uninformed as I am, I have seen my fair share of blown power transformers, being a radio guy myself. I'm not saying I'm smarter than an engineer (although in a few years I will be an engineer!), but would you argue with me that failure is more prone to a transformer with a 9A load than a 7A load?

I will NOT pay for a new transformer unless my power transformer dies. And I hope that doesn't happen anytime soon!

Kyle

Granted a failure is more likely the heavier it is loaded. I would suspect that the engineers that designed the transformer took all factors into consideration. I have no problem loading the transformer to 8.9A even considering the peak upon startup. Its rated for it and I've done it.

antiquekid3 wrote:Well, as uninformed as I am, I have seen my fair share of blown power transformers, being a radio guy myself.

Then you have an advantage over many audio people that don't know the meaning of CCS and ICAS ;-)

Cheers!

Sorry, I had to look those two up! :-) I'm 17, but I've been repairing antique electronics for the last 4 years or so. I can read a schematic well and have a fair idea about tube theory...I've got a lot to learn!

Today, the rest of my resistors and my new chassis came!! I'm hopefully going to get started assembling it soon, but first I need to get a circuit-board-sized metal plate to make my driver circuit on (the Blackburn circuit).

I'm really excited!! I know I will enjoy this amp all through college and onward!

Kyle