bernbrue

Re: [BUILD] STA LEVEL PCB OFFICIAL BUILD & HELP THREAD
« Reply #440 on: February 04, 2020, 06:46:28 AM »
Oh, then it needs to be replaced. The TL783 is fine here. What is the max voltage of the caps in your psu and on the mainboard? Check the (wiring of the) resistors for dropping down the voltages as well. The psu needs to be under load, otherwise the voltage can go up quite high.
Bernd


zero

Re: [BUILD] STA LEVEL PCB OFFICIAL BUILD & HELP THREAD
« Reply #441 on: February 04, 2020, 07:40:59 AM »
Oh, then it needs to be replaced. The TL783 is fine here. What is the max voltage of the caps in your psu and on the mainboard? Check the (wiring of the) resistors for dropping down the voltages as well. The psu needs to be under load, otherwise the voltage can go up quite high.
Bernd

The caps voltage is 450v,
Ill replace the TL783 and check the wiring, what bugs me is that it was working fine.
I see! the voltage under load , when it worked fine, 290v, now it´s 385V, with no load 440v ( normal? )

So there is no other way of dropping the voltage from the xformer other than the 3 resistors i have in series after the diode bridge? just a proper transformer?

The only thing i did, before starting to blow fuses, was replacing the R32s with a 18k resistor so i could get more compression with lower input.
Thank  you.
Kind regards,
Pedro.

zero

Re: [BUILD] STA LEVEL PCB OFFICIAL BUILD & HELP THREAD
« Reply #442 on: February 23, 2020, 12:12:21 PM »
Hi Bernd,
Sorry for being such a pain but i´m a little noob at psu design and i am trying to understand  how this circuit works.

i want to calm down the beast as it produces excessive heat, even the front panel gets hot from the 3 resistors in series i have to tame down the dc after the rectifier.

My thinking (maybe wrong), from what i get from the schematic:

-The trafo from don audio outputs 337Vac.
-After the rectifier, from the math Vac*1,414, the 337Vac goes to 476,518Vdc.

What i gathered in my head from the  TL783 , it needs a little over voltage to regulate, like 25V and it´s not easy to read with no load.

I really want to cool the thing down so my idea is to put there a 230Vac/200MAh trafo so it outputs 325Vdc ( 230Vac*1,414=325,22Vdc)

Am i thinking ok?

Will a 230Vac trafo be ok or will the voltage drop under load and something like 275Vac be better?

I still didn´t replace the TL783 to see what´s burning fuses but before i do that i wanna sort this out.

Sorry for any hassle or stupidity.

Cheers,
Pedro.