Topic: New Official AMT Thread - page 88. (Read 149453 times)

ETA on the Technobit boards?  Do you even plan on compensating customers with the Technobit board?

The only reason we are trying to debug these boards is because we are trying to salvage what little we got from you!

You sent us junk and we are trying to debug the junk.  

No I take it as the signal and power vias were left uncovered leading to them shorting. Only the thermal xfr vias should be bare. And - due to the thickness of the green/red screen layer that is supposed to seal the boards one damn well better make sure that something bridges the resulting gap between the sinks and the thermal vias.

Ja the buck inductors are supposed to be in contact with *something* to suck out some of the waste heat. Along those lines, got a part number on them? With all that is turning up would be a good idea to make sure they are running under their max dc-current rating. If over it then the cores will saturate and say goodbye to regulation.

On traces near the edges:  If whoever laid out the boards knows anything about EMC basics then all traces will be at least 2x the board thickness away from the edges to close near-field loops. Any closer and emissions goes through the roof from the loops becoming true radiated EMI.

Um, that rather raises a point - have these been EMC tested at all? Not sure if miners fall under FCC much less EU exempted equipment...

What are you saying here?   The manufacturer had exposed vias that assumes the use of a thermal transfer pad.... was a thermal transfer pad used?   

So what are you saying?  We can remove any number of caps leaving at least one and it should work the same.  That way we can add a adequate heat sink.  Not the time piece that it currently has.   

Since I had never gotten one I had requested my Invoice from Alyssa a few weeks ago when AMT was replying. Got it the same day. Dates are correct as is amount they received from me, payment method was wrong. Says was wire xfr but was personal check.

http://www.aavid.com/

Pricy, but fast.
You should have two types of boards.

1st with the 4 caps surrounding the chips.
2nd with the only 1 cap out of the 4 in that location.

- First board- this was the original design, provided by bitmine, which also called for a 12x 1500 cap where you'll see the 12x 560 cap there. The manufacturer ordered this component switch which differed from the bom.

- beneath the 560 caps you'll see another location 170 cap on the first board and 330 on the 2nd version with (1500 caps).

The ability to put a railed heatsink exists on the second version but could not exist on the first.
you - and anyone else working on this - list your question in a simple form which allows for an easy to follow response.


ie.  Which value should this component be - snap a pic or something. End post.

 

Got my order on the way for my plexi-bending stuff... should be here by friday. I will get it setup, and make two cases. One for the full-size 5-card standard design, and one with the 3-card mini design.

Then I will throw everything back into the tower, and show the heat-shroud thing. (Just can't show it running, since I only have a PSU large enough to run 3 cards, and I am down to 2 running cards at the moment.)

Now I have to go to work... I will look for more sources for low-profile, multi-fin heat-sinks when I get back. (I am trying to stay away from the thick heat-sinks, as those just retain heat. You need lots of thin fins, for the greater surface area, to reflect the heat off the aluminum, and into the humidity in the air.)

Also looking for some sheets of thermal-transfer pads, that I can cut-up to match the plates on the PCB's. As opposed to solid shims.

For all the work you are doing to get the design right,  you might as well create your own PCB! 

BTW... what does the daughter board do?  Does it convert GPIO signals on the Pi to something compatible with SPI?  Does Pi support SPI?

I am still looking for one with the correct fin alignments...

That, or one larger one, like the one on the back... (well, not that large) Which can be cut-up to order, so the fins are oriented correctly.

However, they would still need to be mounted, have pressure applied, and be "ground/machined" so that they do not short any of the many components that are along the mounting-surface, around the small chip.

EG, the fins have to run the same way as the air-flow, but the heat-sinks have to be wide, not long. Wide, so they fill more of the air-flow for the width of the card. Because filling the length, just causes air-resistance that makes the air flow around the heat-sink, not through it. Sort of what is happening to the large heat-sink, without a guide to keep the air moving through the heat-sinks. It enters the fins, hits resistance, exits the top of the heat sink to the unrestricted gap between the cards, and flows right around the copper heat-sinks. There is very little air-flow passing through the fins, near the middle of the heat-sinks, due to this. Only on each of the ends.

The individual chips and inductors need one more like this... (but not this tall, just this proportion and alignment)



The one for the inductors has to have holes drilled to make room for the caps, and be shorter. One running the length of the inductors, would run into the same issue as the large heat-sink... the length would cause too much resistance to make it functional, without a guide to keep the air inside of the fins. The air would just flow around it, cooing down nothing, just making more air-noise and drawing more unused power blowing air around all the hot components.

Um....   there is something called 'email' that you can use to communicate to your customers.   

Any comment about the potential short?

About the gap between the heatsink and the board?

What about the small heat sink on the other side?

Or the capacitors versus resistors?

Sigh!  Lots of lipservice no action.

Still waiting to RMA my unit back... never worked.

Redoing the website, integrating a forum for that purpose.

We just want to say that we are watching and do appreciate the time and effort you guys are putting into this. Technical questions from a problem solving standpoint will be answered by us. Anything order related can't be dealt with on this public forum.

Tony, Jason, Richard, you are being very helpful, we highly appreciate it and it won't be forgotten.

No invoice sent to me.

I would not advise using a copper-shim... or any shim, for the moment. (The screws would surely warp the boards, unless you had a similar shim washer on every screw-hole also. Though, that would also run the risk of poor contact, since the screws are so far away from the chips, and there is nothing besides the pressure of the PCB holding the thing against the heat-sink.)

Thermal transfer paste is not the same as thermal-transfer pads. The pads are heavily impregnated with a high thermal-transfer medium, and solid. The paste forms air-bubbles if it is thick, and thus, creates pockets of insulation, like Styrofoam. Shims, tend to react, if they are not the same metals. Thin shims, will react, and dissolve almost instantly. (Except gold-leaf-foil, which is too expensive to use as a shim, as you would need many grams.)

The best thing to use, would be the super-thin thermal-transfer pads, which are a specialty item to order. (Not the standard crap they give you for a CPU or RAM, which is too thick and has fiberglass mesh inside, normally. It will not "compress" without direct "above pressure", which these designs do not have at all. Thus, causing the PCB to warp, which may lift the SMT chips off the PCB, along with the traces themselves.)

Besides, mixing metals is the source of electrolytic corrosion. It creates a "battery", in essence, using the thermal paste and heat as the electrolytic medium. That is why gold-plate touching non-gold-plate is worse then using tinned-metal touching tinned-metal contacts. It is never real wise to use bi-metal components in direct contact with one another. (Especially where heat is applied, which speeds-up the chemical reaction.)

If you ever looked at a copper/aluminum heat-sink, where the copper touches the steel-case of the CPU-case, the copper turns black/green and is all corroded, looking like the moons cratered surface. Unlike Aluminum, which corrodes with a thin and hard patina that protects it. Yet, it is aluminum, so it reflects heat... It is sort of a catch-22. Copper absorbs reflected heat, transferring directly to the bonded aluminum, which then reflects the heat into the moisture in the air, causing the evaporation/humidity cooling that we call "air cooling", which has nothing to do with air at all. (Air is thermally inert, as it is essentially invisible to IR-radiation, which is why you feel IR-radiation from a candle nearly ten feet away, in a room devoid of moisture, but only 1 foot away in a room with normal humidity.)

I have gotten emails, but usually not boilerplate style emails that would be a mass email. I think they were individually handling them.

Yeah... very strange about that invoice.  Maybe these folks are so disorganized, they don't even know which customers they owe them money.   The invoice was created using QuickBooks, previous to that,  it is anybody's guess if they had a system to manage their orders.

Let's be honest,  they don't seem even to have a system to mass email their customers.   Has anyone ever received an email from AMT discussing delayed shipments?   

I just got an invoice too...

Hmm...  coppers shims should give enough spacing between the heatsink and the PCB. 

Also agree with you that there indeed is a gap between the PCB and the heatsink and it is questionable weather the termal paste is enough to bridge that gap.   Coppers shims are easily available on eBay.   

Can you point to some correct sized heat sinks for the other side?

Anyone else get the "invoice" email with the revised dates? Mine was stated at 4/29/2013 when in fact I was promised miners within 3-4 weeks from the original date, in the end I got my miners in early April BUT they don't work and have no confirmation or update on whether I am getting replacements or not. I was offered 2 replacement miners on the 10th, I accepted but have gotten no follow up.


On the hardware side....damn I had not even considered the heatsink as a source of the shorts.....Just an oversight since its such an obvious and needed piece of hardware....alternately, couldn't a small copper plate be inserted in between each chip? Sort of how CPU heatsinks function. Put a copper plate/shim in between the chips and the heatsink it would actually eliminate that particular problem. Both sides greased up to keep it held in somehow. maybe as a getto solution crazy glue the corners to keep it fixed and grease up both sides of the shim to insure contact with both. The copper thermal transfer would work in a pinch and would be a nice workaround to the shorting issues that MIGHT be caused by the heatsink...

Also sorry to hear your card died. This was the same issue I observed in almost every instance (one card was DOA and never worked). Most of the others did the same thing within minutes. The ones I have running now I figure are on borrowed time. The only working miner I have is an Antminer s2. Despite the shipping issues It works well. All parts are solid. AND well built. For ALOT less than the AMT miners were. The irony is the Antminer runs at 1.2 some of the time (usually 1056).