High power regulated, quasi-comp.

[Stocker]

???

The wires on the secondaries are paralleled from the terminals...terminal one has 2 wires, 2 has 2, 3 has 2. I have got to get a digital camera!

Of course I could always rewind for dual secondaires...but that is a bit of a hassle. That could be about 2x 18.5VAC at pretty hefty current. Nah.

Okay, one more stupid question. When selecting a heatsink to be as small as possible: should I design for power passing through the device or just the power wasted by the device... one diode drop voltage x current =W? I am thinking the latter... Plus of course the thermal resistance of the sink, interface and the J-C resistance of the device.

 

[blmn]

Stocker,

By your description, the transformer can have two parallel windings, using the same wire gauge. So, you have to see if it is correct and separate them (many times just desoldering them is enough). In this case, the current capacity of each winding will be half of the total current (2x5A, in your case).

About the heatsink question, your heat sink must be designed for the worse dissipation over the devices and it depends on the class of amplification, topology etc. Here http://sound.westhost.com/articles.htm you can find many hints about ampifier design. I Think you really have to see that.

regards

 

[Stocker]

Oh boy. You need to lend me a camera or come look yourself. the two wires are soldered to spade terminals on the secondary and go to the PCB... not two wires from inside the transformer!

Worst case right... I know, I just haven't quite decided how worse that can be yet. There are a lot of decisions when designing even a simple amplifier! I had of course read and forgotten about the ESP pages (again). One of those had my answer but I don't have time right now for calculations... family time! Thanks.

 

[blmn]

Stocker,

Now it´s clear for me. Ok, when you choose what you want to do let us to know.

Best regards,

 

[Stocker]

I took the core off and unwrapped the secondary's covering... inside the transformer it shows me you were right again. Time to buy yourself a lottery ticket!

There is a pair of windings. They appear to have been wound right next to each other. The end was joined with another set of wire of the same guage and wound on for a few more volts. Looks like I shouldn't have any problem separating them for a set of +/- voltage secondaries (at half-current of course but oh well. The lower single voltage output was apparently wound first and is well buried.

This changes things a little. Congratulations on your correct call of 2 wires inside!

 

[blmn]

Stocker,

Thanks. For this level of current many times the manufacturer uses parallel wires because it´s easier to wind. You´re lucky.

I think a Self´s design could be an interesting starting point.

let us to know the development of your project, ok.

Best regards and a happy new year.

 

[Stocker]

I like the "blameless" part of the "blameless" design, but I also like the current foldback protection as in the HK Citation 16. This is looking more and more like a lot of figuring. OK. I am going to measure the transformer again when I get the thing separated, sorted and put back together.

You've been loads of help so far, so thanks to you as well. It will probably be a while before I can get this amplifier even roughed out for criticism. The shop kick-around amp and another big project get priority right now. Have a happy new year yourself!

I declare and end to this thread!