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Courtiestown - Naim Amplifier (Avondale) Upgrade Project

Graham,

That's kind of what I thought. I had tried to screw suitable bolts down the heatsink threads and come up against "resistance". If I want to secure via these threads then it would be time to break out the metric taps and "clean" said threads.

I can see it being "easier" to drill and tap 2 (or 3) x 3mm holes into the Modular case heatsinks (as are already there) and secure the NCC200 heatsinks using 3mm hex head bolts and suitable washers.

There is, of course, the option of securing through the Modu case heatsink by drilling between the fins. There is a maximum "gap" of 8mm which precludes using a 5mm cap head screw as it has an OD of 8.5mm. On the other hand a 4mm cap head screw only has a diameter of 7mm and so will fit between the fins and will also pass through the 5mm central hole in the NCC200 heatsink allowing for a nut to be used on the other end.

In reality two securings should be more than sufficient...............

Regards

Richard
 
They look like taper taps, sutable for through holes and should start farly easly, for a blind hole a plug tap is needed to get the thread all the way to the bottom, as long as you have cleared the swarf out.
They are carbon steel, not as good as HSS (high speed steel) but taping into alluminium you shouldn't have any problems.


Pete
 
if really concerned about tapping in aluminium use a helicoil or thread repair insert.

commonly used in engineering where the material does not have sufficient strength to be tapped or full toque of thread achieved
 
Good Afternoon All,

One of my other hobbies is restoring old Land-Rovers. Most of the fixings into aluminium are relatively coarse threads such as BSW or BSP. Metric threads do strike me as a bit 'fine' for aluminium and not really up to much tightening before stripping especially down at 3mm and only 7.5mm of heatsink. Even more so if the hole isn't full depth and/ for not fully tapped.

I always acquire taps as a 'set of three'.

See assorted Linn threads for 'Linn tight'...................

Regards

Richard
 
Through-bolt fixings for IC power packages - transistors, regulators etc - are not, should not, be tightened anywhere near the yield point where a 3mm thread strips! Most manufacturers will stipulate a max torque in the datasheet for the package style, and this is to avoid deformation to the die or, worse cracking the package. Its usually about 'just-snug' - and very little more.

Fine threads generate huge clamping force, very easily. 'Linn tight' is an idiocy.
 
True; but you only need about 1.5 diameters worth of thread engagement to realise full clamping force on any machine screw : )

_ and that's way way more than needed for heatsink purposes, per my last comment...
 
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Good Morning,

There's (another) parcel due today from Digi-Key which has the capacitors/ inductors for the MiniCap6's.

There's (another) parcel due from RS with assorted bits including 4mm taps and 4mm stainless cap screws.

Kate collected the transformer from the flat this morning.

Assembly of the 'Voyager' amplifier should then start in earnest.

I've decided I'll mount both the VBE/ NCC200's by drilling holes between the fins of the heatsink with sufficient clearance to get a 4mm cap screw through. Whilst I'm not looking for 'Linn tight' I'll have a better 'grip' with a 2 x 4mm fixings in to the Avondale heatsinks rather than 'clamping' using 3mm screws and oversize washers.

The picture below is of the recently bought CAP6:-

3wRowj4.jpg


I was asking about the size of inductors to fit to the MiniCap6's and figures of 12µH were offered up. I had forgotten I had this picture. The Wurth Electronic devices fitted here are 2.3µH/ 17.3A devices. As I have said elsewhere when you track the various things that have been said and you see how things are.........

The reason this came up was as a result of me trying to find out what value/ wattage SMD resistor to fit to the MiniCap6, if any.

Regards

Richard
 
Good Evening,

Both parcels turned up today, as I type this Kate is en route from work (finishing 1815????) c/w a transformer.

I've built the MiniCap6:-

e9dhZ55.jpg


Having looked at things in the case earlier I came to the conclusion that double stacking might well be necessary if I allow enough 'ground space' for two EI transformers:-

HOIU1e7.jpg


and then the double stacking of the HackerCap's:-

tvsj4v2.jpg


As others will attest it certainly releases valuable space for the toroid and the soft start board.

Regards

Richard
 
Great work !

I always thought that using miniCap (caps I often see are up to 20000uf) for frontend duty was too much.
Alternatively I'd use one cap 2200-10000uf, is more than enough to have good ripple result.
That would free much space. I also like the regulator / stabilizer Les introduced in NCC300, neat and space saver. I'm intrigued to design a board of my own having all those in one board which will be bolted in one side of the chassis, so all the bottom of the chassis will be left free for transformer and main cap bank.

Those SMD resistors (1W each) are bleeders if you want to discharge your cap bank fast you use them.
Les boards always had ones installed.
 
ramona said:
I always thought that using miniCap (caps I often see are up to 20000uf) for frontend duty was too much
Click to expand...
.

I should share your view, even more so with what a separate EI transformer would add, over and above, a separate winding off a common toroid. There are a number of things said which aren't always borne out in reality. Unfortunately the only real way to find out is to try it out for yourself.

It would be nice to get access to the NCM1 board as a DIY option.

Been juggling with things this morning. On paper the case I have is 'large' but not that large:-

MY0J9As.jpg


The space bottom left is for A.N.Other EI transformer (not yet delivered).

Later today I'll try and get the VBE and NCC200's bolted to the sides but I don't think double stacking anything is going to help. Still got to figure a route for the mains wiring.

Suggestions welcome.

Regards

Richard
 
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Good Morning All,

Following on from the above, this is the 'jury rigged' set-up of the VBE and NCC200 (OK so the board shown is a NCC220 but is the only one currently mounted to a heatsink that I had available).

ipb1moW.jpg


Conveniently this puts the VBE mounting holes opposite the largest (end) gap in the heatsink fins meaning my though drilling can be a little less precise.........

Regards

Richard
 
I would swap the NCC200 around the other way, so the heatsink is toward the back. A number of reasons:
  • The output stage power connections with CAP6 will be closer.
  • The input stage power connections with the VBE will be closer.
  • The signal output connector is closer to the Velleman.
  • The heatsink will be further than the VBE's heatsink (although this won't make a massive difference, given the size of the Dissipante's heatsink)
Yes, the signal input will be further away from the back, but it's still not far, and you are probably using shielded cable.

You should also spin the MiniCap around, so its transformers are able to connect closer. It does mean the smoothed supply from the MiniCap has to feed back to the VBE input, but you can run those up and to the outside, avoiding the traffos for the most part.
 
Mike,

Thanks for these pointers. The transformer lead outs will reach the MiniCap6 terminals either way so yes I can install it 180° round from this picture.

Yes shielded cable fro the inputs to the NCC200's. Plan B is that I'm fitting straight through RCA connectors and not bothering with the XLR now so will scavenge an audio lead to make these cables up.

I'm out in the shed doing the drilling works. First off a pencil rubbing to assist heatsink drilling:-

zRWdVYc.jpg


Then a clear work bench (it certainly didn't look like this before the photograph was taken) :-

QONDxtH.jpg


Work in progress, had to come in as I'd forgotten to put the M3 nuts back in the box and decided to have a cup of tea whilst in...... :-

L8fGeyv.jpg


Regards

Richard
 
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Good Evening All,

Time for dinner, base plate almost complete........

xAGkvMI.jpg


I'll be back out after dinner to get the Velleman fitted and drill the case side heatsinks.

Tried to find out information relating to the fixing centres for the other EI transformer (75VA against the 100VA shown) - no details available on the RS site.......... I don't really want to pull everything apart to drill four holes..........

Regards

Richard
 
Good Evening All (again),

More progress this evening after dinner.

That's the base plate complete:-

xP2E0x2.jpg


Then on to fitting boards to the side heat sinks. This picture shows that the board heatsinks need the threads "cleaning" before fitting:-

SjkwTd3.jpg


Boards fitted to one side:-

iqfmLko.jpg


Bolts through heat sinks:-

C3ZYkhP.jpg

More tomorrow.

Regards

Richard
 
with every NCC-XXX Les supplies a tapped C channel heatsinks and a 3mm St/St Allen bolt, so by drilling a 4mm hole in the centre of the Modushop heat sink fins the head of the 3mm Allen bolt just fits nicely.
Its worth de burring both heat sink holes so you get a very close contact between both surfaces with a light smear of heat sink compound, From 2014
voyager 10 by Alan Towell, on Flickr
Alan
 
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