Power supplies and transformers

guidobartolucci · 1st April 2006, 07:41 PM

First of all, I'm sorry for my (possibly) stupid questions.

I've started building BrianGT's 3886-based amp and power supply and everything has been going great, but I've never worked on an electronic project that has involved AC and that's making me a little scared so I'd like a little help before I proceed. I bought a toroidal transformer and I think I've figured out how to hook it up, can you please tell me if I'm correct. The transformer has the following picture (please admire my beautiful ascii art :-)):

Code:

BLU ----- | ----- BLK 0V
    -   | | |   -
        | | |
GRY ----- | ----- RED 25V/6.6A
          |
2X115V    |
          |
VIO ----- | ----- ORA 0V
    -   | | |   -
        | | |
BRN ----- | ----- YEL 25V/6.6A

The power supply PCB has 'AC1' and 'AC1-' (the dash signifies the hat on the PCB (I'm assuming that it's a significant mark)) and 'AC2' and 'AC2-'. I am assuming that I connect Black to 'AC1-', Red to 'AC1', Orange to 'AC2-', and Yellow to 'AC2'. Then I connect both Blue and Violet to one of the AC inputs, and both Gray and Brown to the other. Is this correct? Also, on which one of the AC inputs does the fuse go or does it even matter? And what do the dashes on the left side of diagram mean, there's no positive and negative leads in AC right?

BTW, this forum kicks ***, I've been lurking for a few weeks now and learned a lot.

guido.

lndm · 2nd April 2006, 07:18 AM

What you have said sounds good.

Could I suggest you find a mains primer to read? There is a sticky one here. (Not because you sound like you need it or anything

)

It is good practice to fuse each side of the xfmr. Your board should have provisions for fuses after the xfmr, you need to ensure there is fusing before the xfmr. Choose the active lead for the fuse (if you have one in the US, sorry I don't know). Neutral is considered to be closer to Earth. Therefore, while AC is bi-polar, it is not as straight forward as that.

guidobartolucci · 3rd April 2006, 02:16 AM

You are right, I do need to learn more about the mains, but I couldn't find anything on this forum and it's been hard to find anything useful on google. I did read a little about mains in wikipedia, and I found some really good info about transformers and AC power at some other sites, but I can't seem to find anything that has pragmatic info for n00b amp builders.

Like, what exactly does the dash on the transformer drawing signify? Is it the neutral lead?

lndm · 3rd April 2006, 07:05 AM

Maybe they are dots (or meant to be)? If so, they indicate ends of the windings so you can keep them in phase as required.

1st April 2006, 07:41 PM	#1
guidobartolucci diyAudio Member Join Date: Mar 2006 Location: Seattle, WA	Power supplies and transformers First of all, I'm sorry for my (possibly) stupid questions. I've started building BrianGT's 3886-based amp and power supply and everything has been going great, but I've never worked on an electronic project that has involved AC and that's making me a little scared so I'd like a little help before I proceed. I bought a toroidal transformer and I think I've figured out how to hook it up, can you please tell me if I'm correct. The transformer has the following picture (please admire my beautiful ascii art :-)): Code: BLU ----- \| ----- BLK 0V - \| \| \| - \| \| \| GRY ----- \| ----- RED 25V/6.6A \| 2X115V \| \| VIO ----- \| ----- ORA 0V - \| \| \| - \| \| \| BRN ----- \| ----- YEL 25V/6.6A The power supply PCB has 'AC1' and 'AC1-' (the dash signifies the hat on the PCB (I'm assuming that it's a significant mark)) and 'AC2' and 'AC2-'. I am assuming that I connect Black to 'AC1-', Red to 'AC1', Orange to 'AC2-', and Yellow to 'AC2'. Then I connect both Blue and Violet to one of the AC inputs, and both Gray and Brown to the other. Is this correct? Also, on which one of the AC inputs does the fuse go or does it even matter? And what do the dashes on the left side of diagram mean, there's no positive and negative leads in AC right? BTW, this forum kicks ***, I've been lurking for a few weeks now and learned a lot. guido.

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2nd April 2006, 07:18 AM	#2
lndm diyAudio Member Join Date: Mar 2006 Location: nsw	What you have said sounds good. Could I suggest you find a mains primer to read? There is a sticky one here. (Not because you sound like you need it or anything ) It is good practice to fuse each side of the xfmr. Your board should have provisions for fuses after the xfmr, you need to ensure there is fusing before the xfmr. Choose the active lead for the fuse (if you have one in the US, sorry I don't know). Neutral is considered to be closer to Earth. Therefore, while AC is bi-polar, it is not as straight forward as that.

3rd April 2006, 02:16 AM	#3
guidobartolucci diyAudio Member Join Date: Mar 2006 Location: Seattle, WA	You are right, I do need to learn more about the mains, but I couldn't find anything on this forum and it's been hard to find anything useful on google. I did read a little about mains in wikipedia, and I found some really good info about transformers and AC power at some other sites, but I can't seem to find anything that has pragmatic info for n00b amp builders. Like, what exactly does the dash on the transformer drawing signify? Is it the neutral lead?

3rd April 2006, 07:05 AM	#4
lndm diyAudio Member Join Date: Mar 2006 Location: nsw	Maybe they are dots (or meant to be)? If so, they indicate ends of the windings so you can keep them in phase as required.

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