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Question: Shelling a Geneve

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I found in a box of odd hardware 3 metal ti clam shells.

I'd like to put my PFM'ed Geneve in one, but want to make sure I don't short anything or let any magic smoke out.

 

Would it be safe to shell it, and then test for continuity between say the metal screws and all of the fingers on the cards, and maybe all the exposed solder points on the goose neck?

  

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If you don't have the original plastic Myarc shell for the Geneve, I would not use the TI clam shell.  Too many ways to short things out and no physical way to know how close things could be to the shell.  Also, where the back of the card exits the shell, that would be a touchy issue as well.


Beery

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Looking for trouble. Actually, I think someone was making shells at one time. But darn, can't remember who. 

Edited by GDMike

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Weird made a couple of proto shells and sent them to me.

 

They are good quality shells, but (for me ) a couple of bump points need to be resolved.

 

1) the original idea was to put them to gather with self threading screws, that ended up chewing in to the boards, because the four screw holes on back and front aren't perfectly aligned - those are fairly big pieces to print.

 

2) you need some sort of spacer depending on if you have a heatsink under a voltage regulator where a screw goes through.

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If you were going to use any type of metal case there, definitely stay away from the TI cases, as they have some metal bumps inside at dangerous points for shorting out boards. A CorComp, Atronic, or Foundation case would be much less risky--but you would still have two issues: the spacer/standoff issue (those cases come with them already though) and the exit point from the case for the back of the PEB (tape may be enough to solve this last issue), but it is still a bit iffy, as the card really wasn't designed to go into a metal case.

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My cases suffer from material and mfg method related problems.

 

Old, vintage electronics can get quite warm, and that means you need a high temp stable plastic.  There are not a lot of choices for FDM in that category: its really optimized for low temp PLA.

 

My choices, and their pitfalls, are:

 

1) Nylon:  warps when printing due to high modulus of thermal expansion. This throws iff placement of precision holes quite a lot.

 

2) ABS: Has issues with layer adhesion, and does not really print that well, IMO.

 

3) PETG: Expensive, has significant issues with build plate adhesion-- destroys glass beds from over-adhesion, wont stick to coated beds well.

 

4) PVC: produces hydrochloric acid vapor while printing, is very bitchy about print speed and temp, and ruins nozzles.

 

Really, the industry solves these problems with injection molding.

 

To get good results, you would need quality laser resin with a tank big enough, which is $$$$$. 

 

The best I can do is nylon with brass fixtures inside after the fact, sunk in using a quality jig...  lots of bs to deal with material foibles.

 

 

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40 minutes ago, Schmitzi said:

I was happy to unshell my Geneve, for a better airflow...

You will not be happy if you pull the keyboard cable or monitor cable or joystick/mouse downward, lifting the front of the card within the slot, which can in some cases shorts out the card.  Even with the cover on the PEB, the card can lift, though I have not tried to measure exactly how susceptible the card in this situation. 

 

15 hours ago, dhe said:

Would it be safe to shell it, and then test for continuity between say the metal screws and all of the fingers on the cards, and maybe all the exposed solder points on the goose neck

This has been brought up a number of times and should probably be in a FAQ (if not already there)

 

You can place the Geneve and similar cards into a metal or composite TI clamshell only if you remove all of the offending nubs and can ensure that the bottom regulators are properly sinked to the clamshell once the two halves are screwed together.  Some nubs provide card support around the perimeter yet these same nubs can short out the traces.

 

Electricians tape may remove some of the risk but I often find that by the next time someone opens the clamshell, the adhesive has failed, the tape has slipped or fallen, and the traces on the back of the card are once again exposed. 

 

Keep in mind that in a closed TI PEB, the card temperatures can certainly be warm-to-hot but so long as you have (1) airflow and (2) proper heat sinks/thermal compound, the cards can typically survive for years under continuous operation. (Lifespan of some components like the capacitors and nearby logic chips may be reduced, depending on the heat stress )

 

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You know... the PVC is a material I have not yet tried for this. (Dont want to corrode/block my nozzle on the chiron)

 

I suppose i could open a window while printing, and I do have spare nozzles. Current nozzle has had a lot through it. I could try it I suppose...

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1 hour ago, InsaneMultitasker said:

 

You will not be happy if you pull the keyboard cable or monitor cable or joystick/mouse downward, lifting the front of the card within the slot, which can in some cases shorts out the card.  Even with the cover on the PEB, the card can lift, though I have not tried to measure exactly how susceptible the card in this situation. 

 

 

yes, thanks for the info :thumbsup: Luckily I always unplug power and wait this "2 minutes" before touching anything

on my old systems. Maybe this prevented me from destroying a lot in the past.

 

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I want to send DHE some other items I have printed for him anyway, and just been complacent on being up during the day to take them to the post office, that is one block away.

 

I am going to do a test print of the PEB shell model with provisions for M3 standoff (and screw), out of the Fillamentum 303 Vinyl PVC... Cura says it will take a whole day to print.  Here's hoping I don't poison myself with the acid fumes, or ruin my extruder.  The color is a kind of.. I dunno... Greenish beige.

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Well, that was a bust in more ways than one...

 

firstly, yes, I clogged the nozzle.

Secondly, my hot end is aparently not 100% metal, and whatever material is in there other than metal, did not like the corrosive gasses one teeny bit-- the whole hot-end degraded, and started leaking, then promptly scorched and clogged.

 

I had a spare hot-end assembly, and extra nozzles, so after much profanity was uttered, and a fairly lengthy strip-down and servicing session, the chiron is in service again, but nope, not gonna run PVC through it again any time soon.

 

Since I had already gotten all the tools out and all that crap, I did some long overdue service on the i3 clone upstairs also. It is now also 100% in working order.

 

So, no. PVC in the chiron is a nono, unless I order a special all-metal hot-end with no stainless steel parts.

 

I might give PETG a whirl some other time though.

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