Chip amp power supply- a beginners guide

[AndrewT]

Hi,

Assemble a bulb tester.
Test the bulb tester alone. The bulb should not light, should not glow and not even very dimly. Check the voltage available at the outlet socket of the bulb tester. This is MAINS voltage - be extremely careful of slipped probes. and wayward fingers tools etc.
All the wiring around/in the bulb tester is Live. Insulate it so that accidents cannot happen.

Connect each of the 6 wire ends of the transformer into separate terminals of an insulated terminal strip.
Attach a two core mains cable and plug top to the ye & ye positions in the terminal strip.
Leave all 4 secondaries with no additional wire, i.e all open circuit.
Plug in your temporary plug top to the bulb tester.
Plug the bulb tester into the mains wall outlet.
Switch on.
Did the bulb stay OFF, or flash very dimmly, or flash brightly, or go ON.
When you have tested your wiring of the primary come back to us, with your bulb results.

[pacificblue]

Originally Posted by grakka

My inlet only have 1 switch. Does it matter if N or L go via the switch? Any of them need to be unswitched.

The usual practice is to put the switch into the L lead.

In Sweden you use mains connectors that can be turned by 180° in the outlet. Therefore it does not matter on which side the switch is, because you never know which side will actually connect to L and which to N. In such a configuration it would be nicer to switch both leads, but that is not obligatory in all countries. Just make sure you don't touch the supposed N potential, because it may happen to be the L depending on the position of the mains connector.

[pirej]

Interested in build Carlos snubberized power supply. The question is:

- Can I use two transformers: 0-28V and the other 0-28V ..... instead of one with two secondaries (2x28V)?
Asking due to a having two such trafo's...

[AndrewT]

Using separate transformer cores will result in a higher transformer regulation.
But your proposal will work.

However, 28Vac and higher regulation probably indicates you have not yet considered worst case PSU voltage. Will you blow up one or both of your chipamps?

[pirej]

Thanks Andrew, just find on this forum in 2007 Your answer about that...

...can use two separate tranformers each with a single secondary.
Just wire each secondary into the ~ of the bridge rectifier.
Then connect one + of a rectifier to one - of the other rectifier.
This common connection is then taken to your audio ground. The other + and - become your PSU supply points. ....

[pirej]

Sorry, 2006 was the year...link:
how to Using single secondaries transformer for snubber psu

My mistake, the trasnformers are 0-25V, not 0-28 V...Thnx...

[AndrewT]

The law of averages suggests that some of what I post will be useful to some at least some of the time.

[Baztien]

Hi all,

Afer some reading of this forum I'm still confused about how I should size my fuse.

I'm gonna use a 72VA 2x12V transformer to supply a velleman K4003 amp kit (TDA1521) which uses AC current directly and has 2x30W max power output.
I'm not planning to use a soft start.

I calculated my primary fuse rating by doing 72VA/250V=0.28 so I choose a 250mA Slow Blow fuse.
Is this correct? and also is it suitable when testing the power supply?

Do I need to put secondary fuse? how can I calculate the size? should it be slow or quick blow?

Thanks in adavance

[AndrewT]

Hi,
A motor and/or transformer should have the fuse rated at three times the nominal maximum current.
Try T800mA or standard 1A

[digits]

This is from the datasheet of a garden variety 2A slowblow fuse.....