help to power my diy amp kit - Page 2

KMossman · 8th February 2013, 03:44 PM

Quote:

Originally Posted by pistolpedro

I also need to know how to wire the fuse holder and on off switch to the torodial transformer.

hot AC --------------------switch---------fuse-----transformer primary

hot ------------------------------------------------transformer primary

johnr66 · 8th February 2013, 06:26 PM

Put the fuse before the switch.

KMossman · 8th February 2013, 10:22 PM

Quote:

Originally Posted by johnr66

Put the fuse before the switch.

Why?

If you need to change the fuse, then it would be 'live'. You need to remember to unplug..............

johnr66 · 9th February 2013, 01:36 AM

There are IEC power connectors available with a little fuse drawer and the little round fuse holders that when wired correctly are a non shock hazard. It is always best to fuse a circuit as close as possible to where the power enters. Imagine someone probing around inside a device with a screwdriver and it accidentally makes contact to the lug on a switch and to ground. With the fuse after the switch, there is no protection and there will be a nice light show. I see some really cobbled together circuits by newcomers and even kids. many don't even have a fuse. I can imagine a part or wire coming loose and contacting an unprotected switch lug. Not good.

KMossman · 9th February 2013, 01:44 AM

Quote:

Originally Posted by johnr66

Imagine someone probing around inside a device with a screwdriver and it accidentally makes contact to the lug on a switch and to ground.

Fair point - for those who have no idea what they doing - for those I highly recommend ONLY battery powered projects - less than 12V !!!

But I still stand on my view

Any-one dumb enough to go jabbing a screwdriver around a live circuit almost deserves a rude awakening.

johnr66 · 9th February 2013, 02:04 AM

I see a lot of posted pics of what I'd consider poor construction. One common hack job is where they bolt the IC to a heat sink and the circuit board is held only by the leads of the IC. One guy shipped his amp and the vibrations broke the leads. Dangling by the wires, the board can flop anywhere in the chassis. Another is the use of tape and/or glue. You get the idea.

If you are confident in your construction and the potential of someone poking around your circuit someday down the road, by all means, put the fuse after the switch.

KMossman · 9th February 2013, 03:59 AM

Quote:

Originally Posted by johnr66

I see a lot of posted pics of what I'd consider poor construction. One common hack job is where they bolt the IC to a heat sink and the circuit board is held only by the leads of the IC. One guy shipped his amp and the vibrations broke the leads. Dangling by the wires, the board can flop anywhere in the chassis.

ABSOLUTELY! Some guys construct thinking their stuff will never be moved, and works in zero gravity!

Quote:

Another is the use of tape and/or glue. You get the idea.

TAPE?! I shudder................

Glue? depending on the glue.may not be SO bad. I sometimes resort to [generous amounts of] hot glue!

pistolpedro · 9th February 2013, 04:31 PM

Thanks for all the replies. I am really happy im getting help here.
I am very interested in this small little project because it is new for me and i love to learn new things.

take a look now in my diagram how i have guessed the cable connections.
have i done completely wrong?
the toroidal transformer have four input and four outputs.
i have 3 leads from my main 230v ac.. brown, blue and a yellow/green ground.
and i am guessing i have to connect 3 leads to the amplifier also.. 12v AC, ground, and 12v DC again.
what colors to connect where?
do i have to bridge some wires on the transformer? or just leave the unused cables isolated?

johnr66, if i had knew what a 24v ct 50va transformer was and it is cheaper and more suitable to power my amp i would have used that one instead.. but i already bought the torodial transformer so that is what i have to stick with.

btw i am not a suicidal kid. just a noob when it comes to electronics at the moment, but i wish to change that.

thanks again for your patience.

KatieandDad · 05:05 PM

NO STOP.

The Green and Yellow Earth connection MUST NOT be connected where you have shown it.

Connect GREY and VIOLET together and insulate the connection.

Green and Yellow Earth should be connected to the metal work of the chassis.

Connect Vsec 1 to 0V so that the secondaries are in series.

9th February 2013, 05:00 PM	#19
KatieandDad diyAudio Member Join Date: Nov 2011 Location: UK	NO STOP. The Green and Yellow Earth connection MUST NOT be connected where you have shown it. Connect GREY and VIOLET together and insulate the connection. Green and Yellow Earth should be connected to the metal work of the chassis. Connect Vsec 1 to 0V so that the secondaries are in series. Last edited by KatieandDad; 9th February 2013 at 05:05 PM.

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8th February 2013, 06:26 PM	#12
johnr66 diyAudio Member Join Date: Mar 2009	Put the fuse before the switch.

9th February 2013, 01:36 AM	#14
johnr66 diyAudio Member Join Date: Mar 2009	There are IEC power connectors available with a little fuse drawer and the little round fuse holders that when wired correctly are a non shock hazard. It is always best to fuse a circuit as close as possible to where the power enters. Imagine someone probing around inside a device with a screwdriver and it accidentally makes contact to the lug on a switch and to ground. With the fuse after the switch, there is no protection and there will be a nice light show. I see some really cobbled together circuits by newcomers and even kids. many don't even have a fuse. I can imagine a part or wire coming loose and contacting an unprotected switch lug. Not good.

9th February 2013, 02:04 AM	#16
johnr66 diyAudio Member Join Date: Mar 2009	I see a lot of posted pics of what I'd consider poor construction. One common hack job is where they bolt the IC to a heat sink and the circuit board is held only by the leads of the IC. One guy shipped his amp and the vibrations broke the leads. Dangling by the wires, the board can flop anywhere in the chassis. Another is the use of tape and/or glue. You get the idea. If you are confident in your construction and the potential of someone poking around your circuit someday down the road, by all means, put the fuse after the switch.