Deskamp power supply schematic. - Page 3

I intend to get into making my own boards in the future but I am glad I can make this on a protoboard as I have a few on hand and am not really up to getting into making my own this month.  Maybe next month.

OK, stupid question here, but I'm afraid that I might really fry something if I guess at this and do it wrong.  On the case-mounted power jack I know the middle, slightly upper-offset pin is ground, but which is positive and which is negative?  Or does it not matter as long as I stay consistant with it?  Or perhaps does it not matter and only the power coming out of the transformer matters?  Or is it only the power coming from the rectifier bridge?  If I had to guess with my limited knowledge I would guess that as long as I stay consistant through the rectifier bridge that it doesn't matter.  The power doesn't actually have a positive or negative until the rectifier gives me a DC waveform.

Thanks for the AC 101, Avro, you've seriously been a HUGE help in my journey so far.  I hope you won't mind me continuing to call upon you for guidance in the future.  I've been doing some Google hunting on the transformer I bought which is an 8-pin transofmer and it seems in order to get the power ouput I desire I need to connect the primary and secondar coils in series.  In order to do this I connect the hot wire to pin 1 of the primary coil, neutral wire to pin 4 and bridge pins 2 and 3 together and then do the same on the secondary coils.  Would this be the correct act?  This should (according to the datasheet) give me 40VCT at 250mA.  Speaking of which, what is VCT and how does it relate to voltage?  I noticed that that acronym was only used on the series connection voltages and not on the parallel connection voltages.

Hmm... looking at the KBU8K Rectifier, it has 4 pins, which I had expected to be Live In, Neutral In, Positive Out and Negative Out... but on the rectifier it is listed as - ~ ~ + respectively.  Not sure what the two ~'s are supposed to represent?  Or is it that - is negative out, + is positive out, and the two ~ are for Live and Neutral... in which case does it actually matter which order they are put in?  Also, does this run hot enough to need a heatsink?

I know it's a small thing, but I am VERY happy with how this turned out.  I tried to keep it as professional looking as possible.

OK, so I jumped the gun on this.  Couldn't help myself.  Did a bit of research and had to have fun.

So the ground from AC doesn't provide a true ground for the amp.  I guess that makes sense since it's a different kind of power (AC versus DC.)  If I gound AC to the case, what will that do to any components I have mounted to the case that have metal casing (tied to ground) that I had connected to virtual ground before?  I just need to insulate them, right?

On the topic of the transformer and voltage, I see what I did wrong on the primary coils.  I should have known better and feel a little silly for wiring for 220V now.  So I need to wire the primary coils in parallel for 110V, but the secondary coils in series in order to get the full 40V, right?  That will make it 110V in and 40V out at 250mA.  What is the benefit to using a center tap?  I had thought that that had to do with making a better-balanced dual-rail system, but I'm finding what I thought I knew a bit turned upside down at the moment.

Actually, to put my foot in my mouth, I had thought that the center tap was for the ground of the amp.  Now that I look at your circuit again, it seems it's running with a virtual ground, after the rectifier.  Since I want to run my amp at 30V I need to use the series wiring on the secondary coils and use the regulators to step it down, right?

Ah ha!  I get it.  So the ground from the AC jack would be wired to the case (or not, since it may cause more problems than anything... this is not actually necessary?)  The two AC lines coming from the jack would go to the transformers primary coils wired in parallell and the secondary coils wired in series.  However, instead of jumping pins 6 and 7 (two center pins on the secondary coils side) I would tie them together and run them out as the the ground to the rest of the circuit.

OK, thanks, Avro, again.  I seriously owe you one.  If I ever meet you, I'll have to buy you a beer.  At LEAST.

OK, finished re-soldering the leads.  Tried to keep it clean again.  Not as pretty a job this time around, but I'm still happy with it.

As an aside: would it be wise to incorporate a fuse in between the wall socket and the transformer?  In regards to the power switch, should I wire it between the wall socket and the transformer or between the transformer and the rectifier or perhaps between the power supply circuitry and the amp?  All the options would seem to do the same thing, but maybe not in the same way or with the same side effects.