Calling solder experts. What to do?

[riotubes]

Please let me you thoughts on how to solder 6, 22awg primary leads (2 leads wired in parallel from each of three transformers) to a 12awg AC mains cable. Note, this means 6 neutral primary leads to the neutral side of the AC cable, and another 6 positive primary leads to the positive side of the AC 12awg cable.

I've been trying to solder the 12awg wires to an insulated ceramic terminal, but the U channels in this terminal are too narrow to accept the 12awg wire...so the mains cable is perched up top this terminal. Then tried soldering 3 sets of two wires (twisted) to the 12awg cable. Big mess. 3 failed attempts. Not sure if my iron tip is big enough? 700 degree temp controlled, 2.5mm chisel tip is biggest I currently have. I have to scrap the ceramic terminal and find a better solution. any feedback much appreciated.

[wolly]

I didnt get your exact problem but try this
1st try to solder all the trafos one after the other ie.from 1st trafo to 2nd,from 2nd to 3rd and so on and from the last one to the mains.

[pinkmouse]

You really need to fuse each traffo separately, so I would just loop the mains to each fuseholder, then run off individually to the traffos. For the neutral, just buy a bigger connection block, certainly in the UK, terminal blocks are readily available at local electrical distributors up to 100A capacity.

[AndrewT]

Hi,
I would certainly recommend the terminal block method.

I also concurr with Pinky. Wire each transformer from it's own mains fuse. (a primary pair fed from one fuse since they are in parallel).

[riotubes]

Here's a pdf picture of how I have the chassis laid out. I have one iec inlet, one fuse holder, an spst power switch and three transformers. All three traffos run to tube output stage, and one has two sec windings, one of which runs to dac board.

OK. I need a bigger terminal. However, I'm having issues soldering these six leads onto this 12awg wire. I've been trying to do this by stripping 1 inch of the insulation off the end of the wire, and soldering six leads to this. First, I'm not sure if my 2.5mm tip (.1inch) is able to heat the 12awg wire sufficiently as the solder tends to just spread evenly over the wire surface. Second, when I am able to solder 1 of the twisted pair trans leads to the large wire, when I go to heat the 2nd joint, the 1st joint dissolves and I loose the connection.

Now, what Wolly suggested would help immensely, but I didn't know you could daisy chain the primary leads together for multiple transformers with different voltages? I've posted a pic to attempt to communicate more info.

I haven't seen this dac implemented with 3 fusues. How would I do this, and is this "essential" or fall into "ultimate design" territory?

[AndrewT]

Hi,
do not solder the transformer primaries, that will make maintenance more difficult.

Move the safety earth up beside the IEC inlet.
DO NOT use the safety earth as an audio ground!!!!!!!
For those long mains cables consider a second layer of insulation, although not strictly necessary, double insulation here is safer.

[wolly]

Firstly daisy chain on the primary side will not hurt anything,it is in fact a parallel connection.
Secondly tell what you have on the trafos primary,are they pins or terminals or wires coming out.
If you have pins you can twist the wire ends like a coil for both the wires and then solder or you can hold both wire together and try soldering.

[riotubes]

Wolly - the primary leads are 22awg stranded wire with your typical insulation, each lead is about 6 inches long. If I were to solder 5 leads to 1 lead, and then solder the "main lead" to the 12awg cable, could I space the solder joints say 1/2" apart...that be five solder joints over 2 1/2" on the "main" lead...or do they have to be real close together.

Andrew - if I did not solder the traffos primary leads, would you suggest crimping them to the 12awg ac cable? if so, what kind of crimping connector wound you envision? Would this be a metal sleeve that accepts 12awg on one end, and 6, 22awg leads on the other...and then heatshrink over it? I do have a nice crimping tool handy.

[dangus]

I'd consider crimping fork or ring terminals to the transformer leads, then making the connections on a barrier terminal block. It'll look tidy, and be easily removable for servicing or mods.

Barrier terminal blocks:
http://www.allelectronics.com/matrix...ow_Strips.html

[riotubes]

Thanks to all who took the time to post. I ended up getting a barrier terminal block and some captive O crimp lugs. Very clean solution. Thanks for your help.