5 - Building the power supply
barry (Administrator) 12-30-2013 at 01:55 PM.
Post: #1
In the N5X, we build and test the power supply (including the smaller turret board and the VVR circuit) before building the rest of the amplifier. Start by gathering up the turret board and the following components:
* R20
* R22
* R23
* R24
* R25
* R26
* C13
* C16
* C17
* D1
* D2
* D3
* D4
* the bare bus wire

The first job is to add two lengths of bare bus wire to the top and bottom row of turrets, as shown here. Solder each wire to the side of the turret that it passes, eight solder joints in all.

[Image: n5xps01.jpg]

TIP: Amp builders have their own technique but if you're not sure, you can weave the wire around the turrets (as shown above), and at each end wrap the wire around the last turret.
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barry (Administrator) 12-30-2013 at 02:02 PM.
Post: #2
Add power supply components
Now trim and solder the components to the board, as shown in the diagram below.

[Image: n5xps02.jpg]

A few notes to help you:

1) For diodes D3 and D4, it’s best to solder them to the sides of the turrets. This leaves the turret hole available for you to add the high voltage supply wires.

2) Pay attention to the orientation of the following components: C13, C16, C17, D1, D2, D3 and D4. Make sure they are connected as shown in this diagram. (If you've ever made an Amp Maker kit, pay special attention, because this set of three capacitors are the opposite way around to kits such as the WF-55, SE-5a, PP-18, etc!)

Now mount this turret board in the chassis. Use an M3 shakeproof washer and M3 nut for each of the four mounting points.
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barry (Administrator) 12-30-2013 at 02:09 PM.
Post: #3
Initial power supply wiring
There are three sets of wires from the power transformer. The first two sets connect as follows:

1) Green + black + green wires to the 3-way tagstrip close to the first rubber grommet. Trim each wire and solder it to the relevant solder tag.

2) Brown + yellow + brown wires to the turret board as shown here.

[Image: n5xps03.jpg]

For each of these wires, it’s best to tin the end with solder and then bend it to create a ‘hook’ that you can place around each turret shaft - shown here in step-by-step form). Use needle-nose pliers to crimp the hook around the shaft of the turret and then solder it into place.

[Image: n5xps04.jpg]

Then connect the VVR circuit's Power control (VR6) to the turret board with three wires as shown here. Solder lugs 2 and 3, but leave lug 1 unsoldered for the moment. As usual with hand-wired amplifier layouts - in general it's best to keep wires as short as possible and routed directly. Avoid unnecessarily long wires.

[Image: n5xps05.jpg]
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barry (Administrator) 12-30-2013 at 02:51 PM.
Post: #4
Mains-side wiring
With the turret board properly installed, you can add the On/Off switch (S3) and the neon indicator (L1) to the front panel. (For clarity, the front and back panels are shown here as if they have been folded down, although in reality they are at the usual 90 degrees to the bottom of the chassis.)

The first job is to add three wires to the IEC socket: a short green wire to connect the Earth lug directly to the grounding lug next to the IEC socket, and a brown and blue wire to the Live and Neutral lugs. Run the brown and blue wires along the side of the chassis to the On/Off switch, twisting them together and solder them to the top pair of lugs on the On/Off switch.

[Image: n5xps06.jpg]

[Image: n5xps07.jpg]

Then connect the six remaining wires from the power transformer. First, choose the correct two wires for your mains supply:
* 100V = white and blue
* 120V = grey and blue
* 220V = brown and blue
* 230V = purple and blue
* 240V = orange and blue

Run these two wires over to the On/Off switch and trim and connect them, one to each of the switch's centre lugs. Don't solder them just yet, however. (The diagram here shows a 240V connection for UK, Australia, etc.)

[Image: n5xps08.jpg]

You now have four wires left over, the colours will depend on those you chose for your mains supply of course. Run these four wires to the four turrets on the right of the board. Trim them to length and solder them now. (If you move to another country with a different mains supply, you can alter this wiring in the future.)

[Image: n5xps09.jpg]
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barry (Administrator) 12-30-2013 at 02:52 PM.
Post: #5
Wiring the neon indicator
Prepare the neon indicator for soldering by gently prising the two solder tags away from the black plastic - use a thin-bladed screwdriver. This makes it easier to add a wire to each tag's solder hole.

Find the thin brown wire in the wire pack - the type that has just a single solid strand (instead of the thicker multi-stranded type). Solder two wires to the neon indicator, one to each lug and then twist them gently together and run them across to the centre lugs of the On/Off switch. Connect one to each lug and now you can solder all four wires in place.

[Image: n5xps10.jpg]
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barry (Administrator) 12-30-2013 at 02:57 PM.
Post: #6
[Image: n5xstatic.jpg]

Adding the MOSFET
Next, you add the MOSFET. But before we even touch that, here are some vital safety points:

1) MOSFET devices can be damaged by static, including small charges that build up on your body. If you're susceptible to static shocks, then pay special attention - places with low humidity (air conditioning in use) can be tricky. Here's a site with a useful guide on static: http://www.wikihow.com/Remove-Static-Electricity - each time before I pick up a MOSFET, I touch something that I know is grounded (a radiator, another amplifier chassis that's plugged into the mains, etc) to discharge any static.

2) The #1 tip here is: keep handling to a minimum. Pick it up only when you need it, and do the whole process as a single operation.

3) This MOSFET carries a high voltage on its metal mounting tab so you MUST properly insulate it from the chassis. There's a sticky SILPAD supplied with the kit for this reason.

MOSFETs such as these are modern devices, designed for insertion in PCBs. For hand-wired layouts, it's a good idea to tweak their connection pins to make them easier to connect. Start by creating a solder lug for each of the three legs of the MOSFET. Use needle-nose pliers to carefully bend the legs upwards and round to make a ring or hook that you can more easily solder to.

[Image: n5xps11.jpg]

Now add the sticky SILPAD to the underside of the MOSFET, making sure that the holes line up and the whole of the MOSFET's underside is covered. Then mount it to the chassis using M3 hardware (using the 10mm M3 screw). There are two holes here; use the one that allows the MOSFET to clear the power supply board and orientate the MOSFET so that the 'lugs' are closest to the board. Do not overtighten the nut.

[Image: n5xps12.jpg]

Finally, add the three connecting wires between the MOSFET and the board and Power level pot.
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barry (Administrator) 12-30-2013 at 03:04 PM.
Post: #7
Ground the power supply board
There's just one more wire to add, to ground the relevant components on the power supply board. Take a piece of black wire and connect it from the turret at the negative lug of C16 and connect it to the centre lug of the tag-strip.

[Image: n5xps13.jpg]

Now that the power supply is completed, it should look like this. Double-check your layout against this diagram and make sure that each connection is correct and each solder joint good before moving on to test the power supply.

[Image: n5xps14.jpg]
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barry (Administrator) 01-20-2014 at 04:59 AM.
Post: #8
Direct links to reference diagrams
This guide is written in several sections, ranging from a basic description of the N5X to very detailed instructions on how to build each and every part of the amplifier. I recommend following it step-by-step and paying attention to the tips and suggestions.

However, if you're an experienced amp builder, you may just want to dive into the build and do it your own way. To make that easier - and for easy reference for all builders - this, the last entry on each page, lists the important reference diagrams:

* Schematic
* Power supply board
* Main board
* Finished layout
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barry (Administrator) 01-20-2014 at 06:12 AM.
Post: #9
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