4 - Chassis assembly
barry (Administrator) 12-30-2013 at 02:40 AM.
Post: #1
[Image: n5xkit.jpg]

Getting started
My #1 suggestion in building an amp kit has always been: do a dry run first. So before diving straight in and doing all of the stuff that looks interesting and exciting, do a few test assemblies to see how things go together. This will help you avoid problems that you could have foreseen. trust me, there's nothing worse than having to undo dozens of screws or desolder some components to add an item you overlooked.

That said, in this build guide I will try to describe the most methodical way to build the amplifier. So hopefully you can avoid any such problem. Smile
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barry (Administrator) 12-30-2013 at 02:54 AM.
Post: #2
Hardware overview
CLICK HERE to see a high-resolution version of the image below - a fully annotated chassis with all hardware installed in position. You can follow this directly and/or use the extra tips in the rest of this page.

[Image: n5xhl1.jpg]

Initial hardware
A few items become hard to access once other components are installed so do these first. Start with the two M4 ground lugs shown circled here in red, making sure to bend the ground lug so that the soldering hole will be accessible later.

[Image: n5xch01.jpg]

In each case, use an M4 screw from the outside of the chassis, then the ground lug inside the chassis, then a shakeproof washer and then the M4 nut to secure it.

[Image: n5xch02.jpg]
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barry (Administrator) 12-30-2013 at 02:58 AM.
Post: #3
Turret board mountings
Next, add the hardware for mounting the two turret boards. There are nine 3mm holes altogether, shown here. In each case, add a 6mm M3 screw from the outside, then a shakeproof washer on the inside, then one of the M-F spacers to secure it in place.

[Image: n5xch03.jpg]

Now check that both of the turret boards mount on these spacers. There's a little tolerance ('wriggle room') built into the mounting dimensions, so if necessary you can loosen one of the M-F spacers and adjust it slightly in its hole.

At this point, do not fix the turret boards in the chassis. We'll get to that later.
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barry (Administrator) 12-30-2013 at 03:09 AM.
Post: #4
Other lightweight hardware
In general, it's a hell of a lot easier to handle a chassis-assembly job if you keep it as light as possible for as long as possible. For this reason, add the other lightweight parts first and the heavy transformers later.

Here's the simpler stuff, in no particular order:
* V1 valve socket using M2.5 hardware
* V2 valve socket and retaining clip using M2.5 hardware
* V3 valve socket and retaining clip using M3 hardware (6mm screw)
* 3-way tagstrip using M4 hardware

In each case, insert the screw from the outside and don't forget the shakeproof washers (remember that amplifiers are subjected to a lot of vibration). Make sure to choose the correct size washer for the screw - don't use the M3 washers with M2.5 hardware, or you'll run out when you need them!

Then add the hole cover to the unused hole between V1 and V2 and insert the five rubber grommets. There are two sizes, but it's not possible to get them mixed up.

Now attach the four M6 cagenuts to the outside (top) of the chassis flanges.

[Image: n5xch04.jpg]
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barry (Administrator) 12-30-2013 at 03:22 AM.
Post: #5
Rear panel and components
Just four sockets and four sets of hardware to do here. But it's easier to add your country's mains voltage and the fuse information before you mount the rear panel. Use a permanent marker pen to write in these two pieces of information in the box provided at the right end of the panel. Your mains voltage will be one of 100/120/220/230/240V and the fuse value will be "T500mA".

[Image: n5xch05.jpg]

There's also a pre-printed box for you to personalise your amplifier build in the centre of the panel. Write in your own details here.

[Image: n5xch06.jpg]

Now add the rear panel and secure it in place with M4 hardware with ground lug at the far right end of the chassis (when viewed from the inside), and M4 hardware (without a ground lug) at the far left.

Then add the three speaker output sockets, orientating them so that the solder lugs are all facing out of the chassis for soldering later. Add the IEC mains socket and secure it with M3 hardware (using the countersunk screws).
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barry (Administrator) 12-30-2013 at 03:30 AM.
Post: #6
Front panel and controls
The N5X's front panel is held in place by the main amplifier controls: six pots, three switches, one lamp and one socket. However, for now, install only the six pots to allow easy access for other parts later. (Keep J1, S1, S2, S3 and L1 on one side.)

[Image: n5xpot1.jpg]

When installing the pots, there are a few things to bear in mind:

1) trim the black nylon shaft (B) so that it's about 8mm long - use a junior hacksaw, Dremel with cutting wheel or similar

2) use BOTH plain washers on the inside of the chassis...

3) ...to allow the small locating tab (A) to fit in the small holes in the front of the chassis (bend it slightly, if necessary)

One minor thing to bear in mind: the order of the pots along N5X panel isn't perfectly sequential! The pots are numbered according to the schematic - as they should be - but it's obviously conventional to put the Middle pot (VR4) between the Treble pot (VR2) and the Bass pot (VR3) on the front panel. Smile

TIP: Double-check that you have the single 1MΩ lin pot in the VR6 position for the Power control for the VVR circuit. The two 1MΩ log pots are for Bass (VR3) and Master (VR5).
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barry (Administrator) 12-30-2013 at 03:45 AM.
Post: #7
Mounting the transformers
Add the output transformer, T1, orientating it to so that the speaker wires (orange, yellow, green and grey) from its secondary winding pass through the grommet closest to the back panel, with the brown and red wires of the primary passing through the other grommet. Secure this transformer with M4 hardware.

[Image: n5xch07.jpg]

Now add the power transformer, T2, on the outside of the chassis. Start by removing the M6 nut to allow the M6 bolt to pass through the hole in the chassis. Then rotate the toroid so that the wires are in roughly the correct positions. For the N5X amplifier layout, the thicker green wires of the heater supply go through the rubber grommet that's closest to the centre of the chassis, with the brown + yellow + brown wires of the high-voltage supply going the centre grommet and the six wires of the mains-side primary going through the grommet closest to the edge of the chassis.

This is a bit tricky and rather fiddly. Smile Take your time and insert the wires first and then gently lower the toroid down on to the chassis. Make sure that the second rubber pad sits properly between the bottom of the toroid and the chassis surface. The toroid is secured by adding the M6 shakeproof washer on the inside of the chassis and then the M6 nut.
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barry (Administrator) 01-20-2014 at 05:00 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 06:14 AM.
Post: #9
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