unknown power supply good enough?

[nightanole]

Well i had my heart set on a 3 pound tor style transformer i had in the junk bin, but the voltages didnt work out so i found another traditional style transformer and wanted your opinion on it.

Its a ATS7164 that goes in pioneer vsxd506,vsxd466s, and vsx456 receivers. Its 8.5 pounds and semi shielded (has an extra iron sleeve wrapped around it). I measured 40vac plus center tap. So that should put me right on the mark for my lm3886. Thats what +-28vdc? My other main concern is I need another power supply rated for 24-30vdc and 100va. Would just 1 leg and the center tap fit the bill since its 8.5 pounds? I dont think i can combine a center tap like i can a dual secondaries setup.

[Ty_Bower]

Originally Posted by nightanole

Would just 1 leg and the center tap fit the bill

You don't want to do that. It draws current on only one side of the winding, which leaves standing DC on the transformer. It'll saturate the core and you'll get excessive heating, buzzing, noise in the power, male pattern baldness, and all sorts of other horrible things.

[AndrewT]

Hi,
yes, you can leave one half of the centre tapped secondary unconnected.

Drawing current from one secondary is no problem for the transformer.
Remember to observe the current limit of that secondary.

[nightanole]

Originally Posted by Ty_Bower

You don't want to do that. It draws current on only one side of the winding, which leaves standing DC on the transformer. It'll saturate the core and you'll get excessive heating, buzzing, noise in the power, male pattern baldness, and all sorts of other horrible things.

Uh its only one coil. Wouldnt it just be like a auto transformer that uses multi taps along the same coil for buck boost?

Autotransformer - Wikipedia, the free encyclopedia



I could the problem with an unloaded side of a switch mode...

[nightanole]

Hmm wonder if there is a simple way to get full wave and full bridge out of a chipamp power supply. That would solve the problem.

[AndrewT]

by chipamp power supply do you mean transformer?

[Ty_Bower]

Originally Posted by nightanole

Wouldn't it just be like a auto transformer that uses multi taps along the same coil for buck boost?

The load you put on an autoformer should draw current through all 360 degrees of the waveform. You said you wanted DC, so I assume you're going to put a rectifier diode and some filter caps on the transformer. The rectifier only conducts for half the cycle.

[nightanole]

the chipamp.com dual full bridge with snubber power supply board.

So Ty_Bower your telling me i have to make a full wave (2 diode) to get the 20vac out of the transformer or it will growl?

[AndrewT]

Hi,
the centre tapped transformer can be used with a single bridge rectifier to create a dual polarity power supply.
The centre tap is taken to the junction between the two smoothing capacitors. This becomes the PSU Zero Volts.

You can tap off one polarity for auxiliary use. The total current drawn from that polarity must be within the current limit of the secondary.

If your 40Vac CT is off load measurement then it is probably 18-0-18Vac and expect +-25Vdc when on light load.

Now the second supply of 100VA @ 25Vdc will draw 4Adc. That is a lot of extra load for that half of the secondary!

[nightanole]

They will not be ran at the same time. It will be either loaded with a lm3886, or a 25 volt t amp, but not both at the same time.