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Old 25th May 2004, 05:10 AM   #1
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Default PS wire width

Iím about to wire my first PS. The trannie is 300 VA, with about 34 volts on the rails. I am bussing the PSU caps a side, rather than a star ground.
It was suggested to me that the 0.7 mm (I think thatís 36 gauge) wire I was going to use may not be adequate, and I should use 1.0 mm (25 gauge).

I'd be happy to do use heavier wire, but the only 1.0 mm (locally at Jaycar anyway) is enamelled, which would require a lot of fiddling to remove the enamel at the numerous points on the wire (eg the 4 caps a side).

I could strip the PVC jacket off normal insulated wire, but as my wire is stranded, I believe Iíd need to tin the ends of the wire before you
stripping the insulation from it, to stop it falling apart. Also,
Iím told I should tin the entire length of the wire to prevent oxidation Ė all this is a little time consuming Ė there must be a quicker way

A long term technician has just told me that he thinks 0.7mm will handle about 5 amps. The *output current limit is typically 11.5 amps. I donít know the formula for the current within the PS but imagine it would be a lot less than on the output side of the chip (the LM3886). I'm posting in SS because I think you guys know more!

Do you think 0.7 mm enough, or what would you suggest?

Thanks

Richard
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Old 25th May 2004, 05:27 AM   #2
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rick..how are you going mate ??..im not very experienced, but have been a PSU tech for 3 years now, and as a rule of thumb (as i was taught by the senior engineer), 1mm^2 can handle 5A of current
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Old 25th May 2004, 05:28 AM   #3
MWP is offline MWP  Australia
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0.7mm is far too small, as is 1mm.

The bigger the better, you want to minimise losses in power wiring.
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Old 25th May 2004, 07:24 AM   #4
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Default supplier?

Hi guys
Ė so 1.5 or 2 mm??
Do you know a good supplier of tinned non-coated wire?

Richard
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Old 25th May 2004, 09:13 AM   #5
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Default Oz supplier

FYI:
I found an Australian mail order supplier of 'heavier' tinned wire, and will get some from them
http://www.finnsglass.com.au/home.htm


The largest they have is 16 gauge: 1.3 mm, should be ok.
Someone else had bigger wire, with much larger MOQ.
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Old 25th May 2004, 09:42 AM   #6
lucpes is offline lucpes  Europe
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The rule of thumb is very simple here: as thick as you can get to fit. You can use solder wire-mount pieces to the PSU wires from dismantled screw wire-to-pcb connectors to get 2.5mm for this with a soldered connection without having pcb mounting problems. You need an 100W soldering iron/gun to tin and mount bigger wires in the amp.
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Old 26th May 2004, 12:25 AM   #7
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Default please clarify

lucpes
Not sure what you are describing ("solder wire-mount pieces to the PSU wires from dismantled screw wire-to-pcb connectors") - could you explain more, or attach a photo?

Thanks
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Old 26th May 2004, 12:47 AM   #8
lucpes is offline lucpes  Europe
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1 is 'wire-to-pcb screw connectors'

2 is a connection made by soldering a part I got from dismantling 1 to the 2.5mmwire/pcb

It's very ugly, unpractical if you plan to separate the connections in the future but now I don't have to concern about having additional resistance points which vary with the amount of current drawn from the PS in my 'vewy vewy pwecious wails'.

edit: Sorry, english is not my native language, and I messed it up a bit with the 'thingie that you take from there and do that other stuff'
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Old 26th May 2004, 01:06 AM   #9
Magura is offline Magura  Denmark
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Well, an issue that havnt been addressed here is the type of wire.

Looking at Lucpes's example it seems to be worth mentioning.

The insulation material should be of a reasonable quality and thickness. Personally I never use anything but fibreglass or teflon. Regular mains voltage rated wire should be ok, but in case something gets hot glass or teflon will provide an additional safety margin. I like the thought of that. What also should be mentioned for the same reason is that there is a reason why rectifier bridges have spade terminals, and its not to have more surface to solder the wires to, but to be able to use crimped spade termination for the wires attached to it. Again it for the sake of a decent safety margin in case something goes wrong, or in some cases as with big class A amp, simply cause the load requires spade termination.

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Old 26th May 2004, 01:27 AM   #10
jleaman is offline jleaman  Belgium
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why do people use speaker wire for hook up wire.. WHy .. no one has ever answered this to me but.. Humm... why not just buy the proper wire or strip apart something with proper wire.. i have tons of it i keep all computer psu's and use that wire for hook up wire and it works perfect.. Of course i m buying teflon coated and the ofc silver wire for my Aleph's : O)
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