50w Single-Ended BAF2015 Schade Enabled

[dantwomey]

Done!

 

[cubicincher]

to Dan #1341

Hello Dan;


I am sure that the big IXYS-Mosfets will heat!
Greets
Dirk

 

[toto34]

Good morning, everyone.
What resistance and power value for purge resistance for polarized electrochemical capacitors of 47 000µF/100Volts loaded with 60 V?

 

[Ben Mah]

Bleed resistor value? It depends on how much current you want to bleed during amplifier operation and how long of a wait to discharge your power supply with no load connected.

Use Ohm's Law to calculate. For instance if you want to bleed 20mA, R=60v/.020A = 3000 Ohms, and P=60V x 0.020A = 1.2W. Choose either 3W or 5W. 5W will run cooler.

As for time to discharge if no load is connected to the power supply, there are online calculators. Here is one:

Blocked

For 47,000uF, 60V, and 3k bleeder resistor, time to discharge is nearly 10 minutes.

"blocked" url is an online DigiKey calculator.

 

[dantwomey]

Good morning, everyone.
What resistance and power value for purge resistance for polarized electrochemical capacitors of 47 000µF/100Volts loaded with 60 V?

I used 6.8K 5 watt just because I had some laying around and they work ok. A little slow on the bleed down.

Regards,
Dan

 

[toto34]

Ok thanks for your quick and accurate answers

 

[dantwomey]

The next obstacle for me is...............

My TL431 bias circuit worked well unloaded and or with a 10K resistor as a load. I can vary output voltage and all is fine. When I hook it up to my mosfet circuit it lets out the magic smoke on startup. This is odd because when I use a lab supply for the bias supply all is well.

Regards,
Dan

 

[MEGA_amp]

is the bias circuit going up in smoke or the amp? It wouldnt make much sense if the bias circuit tested fine unloaded, unless theres a short somewhere. Verify the lowest voltage possible from the bias supply before applying power to the amplifier.

 

[dantwomey]

The TL431 is going up in smoke like there is some sort of inrush or a short. Both unlikely since the lab supply doesn't have a problem and show no current draw.

The journey continues...............

 

[dantwomey]

Might have a flaw in my TL431 PCB. More soon..............

 

[MEGA_amp]

got a few spares if you need. Gets powered from the +/Gnd of the LM317/337 buffer regulator, works like a charm.

 

[dantwomey]

Got lots too. Since ZM has me close to the finish line I might do a voltage divider off my +12 supply as a test. Funny, the TL431 seems so simple but I keep melting them for some reason.

Regards,
Dan

 

[Zen Mod]

you can try using string of leds, they have nice negative TempCo, maybe handy for puck gate

say that 3 greens and one 1N14148 in series will cover puck Ugs needs

if you need help for calculating values, just buzz

 

[dantwomey]

you can try using string of leds, they have nice negative TempCo, maybe handy for puck gate

say that 3 greens and one 1N14148 in series will cover puck Ugs needs

if you need help for calculating values, just buzz

Thanks to your help I’ve made great progress so far. Using a lab supply for the bias of the one mosfet things fire up perfectly. However I did learn that Vgs is super sensitive right down to the mv. But once you got it, you got it! If I can remember correctly Vgs for the bottom puck is around 4.12v. A bit lower than I planned for the 5-8V TL431.

Your LED idea intrigues me. I really enjoy trying new things and experimenting.

More tomorrow?

Regards,
Dan

 

[Zen Mod]

just remind me - you have +15V regulated there ?

 

[dantwomey]

just remind me - you have +15V regulated there ?

Nope. +/-12v as recommended in the diagram of the buffer posted in this thread.

Regards,
Dan

 

[Zen Mod]

okidoki, not much of difference for little divider

will use +12V

later, you'll get sketch

 

[dantwomey]

okidoki, not much of difference for little divider

will use +12V

later, you'll get sketch

You’re too kind!

 

[Zen Mod]

Schade amp aux circ for bias

here it is

 

[Zen Mod]

You’re too kind!

nope, quite contrary

I'm just pretending in public