D200 Reassembly thread...

[Manoet]

Spent the afternoon measuring stand-off heights (those little internally threaded posts that were masked off during anodizing for PCB mounting) and Devialet ceiling underside depth & elevation changes. All standoffs are same height when it comes to PCB mounting but there's several elevation/height changes between underside of top and PCB's where thermal transfer pads are used and associated relief areas where the internal ceiling is milled deeper than in other areas There's only two heights of stand-offs (.0935"/2.37mm & .045"/1.14mm) and used primarily on left and right sides of the top (ceiling). And 3 different relief areas or 'elevation changes' that have to be sorted for varying thicknesses of thermal pads and none of them anywhere near the perfect thickness to just be installed and have the PCB screwed down on to them. All my SPENDY high tech thermal pads are ~1mm thick and I'm needing heights like 2.37mm, 2.62mm, 1.83mm etc. All doable of course but means cutting pads slightly undersize on length/width first then stacking/assembling them into 'oversize' thicknesses then rolling them down thinner to sizes a bit closer to nominal then allowing the PCB to 'squish' them to final thickness for maximum contact efficiency and thermal transfer and bringing their desired finish length/width back to specification. Overall over 4 dozen individual pads of varying lengths, widths and compressed heights to be cut, assembled and compressed to a known ideal before installing and finish-compressing to ideal thickness with PCB aluminum mounting screws which still need to be cut to their finished length. Devialet has pads in varying thicknesses at their disposal to work with. Additionally if they needed to cover 4-6 components side-by-side or in close proximity they just slapped one large thermal pad over them all and call it a day. But because I'm running convection cooling I want an air path between all those items instead of an air 'dam' obstructing airflow between small, individual heat generating components. So I'm relegated to doing things the hard/long way. My choice and I wouldn't have it any other way!

A LOT more measuring and math than I'd planned on today but nothing insurmountable... just pesky/testy & monotonous. It'll get easier the further away I get from the Devialet "ceiling." That's how tomorrow will be spent but by then I'll be fresh and do it like I love it which I do but not at this hour after a 14.5 hour day.

[absolutk]

How's it looking Manoet? . We're all curious!

[Manoet]

Its slow-going and after losing my last reassembly-related post I'm a little suspicious of the forum going 'tango uniform' again so I'm dragging my feet a little on important updates as its too frustrating to lose em. Pics are saved of course but any planned or well thought out texts are vaporized and cannot be easily duplicated. I might have an update near the end of today. Certainly no later than tomorrow.

[brit]

Its slow-going and after losing my last reassembly-related post I'm a little suspicious of the forum going 'tango uniform' again so I'm dragging my feet a little on important updates as its too frustrating to lose em. Pics are saved of course but any planned or well thought out texts are vaporized and cannot be easily duplicated. I might have an update near the end of today. Certainly no later than tomorrow.

As you are probably aware, there have been some technical issues with Forum over the past couple of days. Perhaps a quick note to the Forum admin might throw some light on your missing "Post" - although you may already have been down that route?


David

[Manoet]

After mentioning it three times and having seen the admins at those post sites and no word I'm assuming the worst. But having talked with a forum member via PM who got mistakenly assigned as the author of my missing post and deleted it unknowingly I'm reasonably confident its gone forever. I'm just being ultra conservative in risking the same thing again so soon after the latest failure.

[GuillaumeB]

After mentioning it three times and having seen the admins at those post sites and no word I'm assuming the worst. But having talked with a forum member via PM who got mistakenly assigned as the author of my missing post and deleted it unknowingly I'm reasonably confident its gone forever. I'm just being ultra conservative in risking the same thing again so soon after the latest failure.

Who is the other forum member and when did this happen? More details would be helpful here.

As far as I know in 1 year and 5 months of operation this is the first time that a post has been lost. I did once delete a post by mistake when trying to move it to a different thread but that's about it.

We have had some maintenance issues over the past couple of days but as far as I know these haven't resulted in any lost posts. 

Guillaume

[Manoet]

Guillaume I think it would be inappropriate for me to call him out openly at this, or any forum as he's obviously embarrassed enough without making it worse by my going public with his name here. He contacted me privately, via PM, apologized and explained what he thinks happened and given his discretion, I suspect he can't want me being more public and less discrete than he has chosen to be. Ideally, when he reads your concern I'm confident he'll contact you as he did me, privately. Fair enough?

BTW the deleted post was submitted between 6 & 8pm Tuesday evening (my time) so woulda been the wee hours in the UK. Then the 'deletion' happened very early (my time) Wednesday morning when the forum clocks were all outta whack and post responses were being displaced on top of instead of under previous posts. Besides him there's a number of others that saw the post and the pic before it disappeared and shouldn't be too difficult to confirm that if some of them would come forward voluntarily, publicly or privately to you.

The following pic was used in that post:
   

[Manoet]

    I'm sorry for not being able to post anything Friday or yesterday as promised but I hit a snag late Friday afternoon that had me putting on the brakes until I understood it better. I found 2 inductors shown in pic with the edges of their top covers lifting. On further examination I found they were almost falling off on their own as I was able to coax them off just by gently lifting with my fingertip at any/every edge... ya might say 'dangling by a thread.' Once inside I could see the what was once crystal clear adhesive used to keep those covers applied to the ceramic-ferrite (highly magnetic) boxes that house the inductor windings was compromised. That is to say the adhesive 'squares' had started to yellow, heat-harden and become brittle. This on a brand new D200 that only arrived June 1st this summer and has been out of use for more than a third of its time with me. Needing to understand this better I halted reassembly forthwith and spent yesterday researching this part which is made by "Coilcraft" and labeled H36-0325L/1434D. It must be an inductor proprietary to Devialet as nothing was publicly available but the "D" does seem to represent "digital" on other similarly numbered inductors from Coilcraft. Virtually EVERY part marked with a "C" inside the Expert series comes from Coilcraft and there are dozens!

As to this issue I'm still debating how I should proceed. I could use a 100% silicone adhesive around the tops to resecure them and have no worries about them coming loose again due to the working temp of silicone at 450*F/232.2*C. Near as I've been able to determine the adhesive Devialet/Coilcraft used is rated at 70-100*F/21-38*C. We all know that dog can't hunt for very long inside an expert! Another thing I may try is a small/thin pin heatsink on top of each inductor housing or a single rectangular one placed atop both with Arctic Alumina heatsink adhesive. Think of "AA" as a true 2-part epoxy heat-transfer fixative for heatsinks. Or some variant of the 2 options mentioned above. I'm going to take the day to to watch American football and mull it over.

You can easily see in the pic how the factory adhesive has yellowed... is drying out and becoming crispy/brittle as most adhesive quality has dried up. The 'covers' used over these inductors are nothing more than paper. An intermediate layer with the inductor model number printed on it adhered to a top layer which has been painted/coated black with perhaps some EFI/RMI or heat-resistant resistant paint. The black side is what you see on top of the inductor if you pull the belly pan. It gives the illusion of being a solid black square that is 25mm square X 8.5mm thick.

No intent on my part to cry wolf here as I have no idea what would happen, if anything, were either of these inductor covers were to separate/detach and fall off the inductors in normal use as they would simply fall down into the underside of the belly pan. Don't know if errant EFI/RFI would increase or heat would become a bigger factor. All I know is either Devialet or Coilcraft went to some trouble and expense to attempt to cover these inductors and my intent is to improve on their effort and better it if possible.

My remedy will be disclosed at some point after I've done it either by text or self evidenced by virtue of an updated picture. My reassembly has been plagued by several issues such as this and its painfully slow-going. I've determined that several places that had thermal pads before will now be better-served with convection cooling instead of conductive cooling since convection cooling is significantly more efficient than conductive and far more efficient than radiant cooling. In same places, especially where 'large' thermal pads were used there's no getting around using them again as they're simply a better option in those places. I'll catch everyone up to what I've done related to this as soon as its been carved in stone.

[Manoet]

In the interest of time savings and not changing things further in a very long line of changes I've decided to re-use the existing paper stickers affixed to the inductors via 100% silicone adhesive. The reasons are four-fold; 1, its the fastest way to get me back on track with reassembly. 2, it changes less than any other option which could be important upon reassembly if I have to go chasing issues that might occur once reassembled. 3, it will provide the longest-lasting repair due to silicone's high-temp characteristics and best insulation around any potential leakage areas. And 4, its a simple matter to gain total/complete access to these inductors from a fully assembled D200 minus its belly pan! Therefore I can easily re-do them seven-ways-to-Sunday if I perceive any benefit at any time post-reassembly with simple belly pan removal. Simply put, at this point in time this method is the most expedient, closest-to-OEM and least invasive/risky of all other options available to me.

[Manoet]

    This picture will prove useful as a reference later today as well as a comparison to the existing method used when the updated pic is added. Its of my original D200 thermal transfer pad layout before chrome stripping. Dunno why Devialet prefers to apply these pads by hand in "blanket" coverage wasting a L-O-T of thermal pad material, covering PCB surface that has no thermal transfer provision and thusly making areas that store but can't transfer heat efficiently. Maybe if they were paying almost $50 per sq inch for this particular thermal pad they'd be more conservative like I've chosen to be. Or better yet they'd invest a couple hundred dollars in steel rule dies that would cut their thermal pads perfectly and allow them to be affixed completely pre-spaced and aligned to cover only the areas needed or more importantly only the areas conducting heat.

Later today I'll begin laying my pads out on the PCB underside... the same way Devialet did originally but the pads transferred to the chrome side after use as chrome is smoother and more polished than the PCB and therefore easier to stick to. I shouldn't have the same problem after assembly as my soda-blasted anodized surface will be a lot less easy for the pad to adhere to and should prefer remaining on the PCB side of things.

Hard for me to gauge sq inch usage of the thermal pad material I'll use at this point but I'm guessing I'll use maybe 60-80% less thermal pad material on mine than Devialet did in this picture. Yet I will completely cover EVERY designated PCB heat-transfer point that they did with their blanket coverage but a lot less non heat-transferring circuit board! Mine will have lots of air space around and through the individual pad installation sites to enhance convection cooling. I've also decided to use a small amount of silicone spray (sprayed into a cup) then dabbed on the thermal pads via a cotton swab lightly on the exposed side of the thermal pads once secured to the PCB. This will act as a thermal interface material that prevents the pad from becoming too attached to the anodized surface and insure if I have to remove the PCB that the pads remain affixed to the PCB instead of transferring to the anodized surface as they've done on the OEM housing. This method allows for repeated PCB R&R without worrying about the pad being torn or pulled apart and damaged during removal if stuck too aggressively to 'both' surfaces.

If thing s go as planned today, tomorrow I'll move to repeating this process inside the PSU cover but there I'm going to experiment with eliminating all but the single primary thermal transfer pad. I'm betting the convection provision I've added there will more efficiently rid that covered compartment of heat than the conductive dissipation Devialet had to work with. If you want to jump ahead you can preview those pics in the PSU posts here in Tweaker's Corner.

Pic(s) of todays work when available...