exxos blog - random goings on

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exxos
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Re: exxos blog - random goings on

Post by exxos »

I have been puzzling why after assembly it always seem to be the chips on the right-hand side of the board which I had to re-solder. I thought at first may be the PCB oven was malfunctioning or something.. But turns out the paste was getting thinner as it printed from the left side to the right side of the board. To the point where there was just simply not enough solder to bridge the gap between the PCB and the RAM chips.

Of course I was checking from above to make sure the pads all had paste on them,But I did not think originally of looking at the board from the side to see if the paste had "enough height" on them.

I did a update to my Voltera a topic on this..

https://www.exxosforum.co.uk/forum/viewt ... 138#p67138

Now I have done this mod to the printer, the board I just built worked perfectly first time. The paste was a lot more consistent height wise across the whole board this time.
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
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Icky
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Re: exxos blog - random goings on

Post by Icky »

Another fix to add to the Voltera forum @exxos.
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Re: exxos blog - random goings on

Post by exxos »

I was looking for a way last night to convert Gerber to a STL file and came across this site https://solder-stencil.me/ Which I guess could be useful for stencils to be 3-D printed anyway..

Reason for this is not specifically to do a stencil, but to do a template 3-D object to help me align the RAM chips or soldering very much like I did in this topic with the STE in simms.


It exports a file like this one, being a STL file it is always made up of millions of stupid triangles :roll:

Capture.JPG
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As I used design spak, thankfully it has a flattened tool to create a solid 3-D object.

Capture.JPG
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So I should be able to edit the pads out and create a big hold for the DRAM ICs to drop into to help speed up assembly of these boards :)
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
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Re: exxos blog - random goings on

Post by exxos »

Getting there :)

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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
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Re: exxos blog - random goings on

Post by Badwolf »

exxos wrote: Tue Jul 13, 2021 7:07 pm Getting there :)
Don't forget to take them off before inserting into the oven. :?

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Re: exxos blog - random goings on

Post by exxos »

Badwolf wrote: Tue Jul 13, 2021 7:45 pm Don't forget to take them off before inserting into the oven. :?
What the template or the chips :lol:
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Re: exxos blog - random goings on

Post by Badwolf »

exxos wrote: Tue Jul 13, 2021 9:39 pm What the template or the chips :lol:
Always fry chips! :lol:

BW
DFB1 Open source 50MHz 030 and TT-RAM accelerator for the Falcon
DSTB1 Open source 16Mhz 68k and AltRAM accelerator for the ST
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Re: exxos blog - random goings on

Post by exxos »

My power supplies went out of stock twice as fast as I had expected :roll: On one hand it is good that there is still interest in them, but on the other hand when they go out of stock in a year as opposed to the projected two years , it means I have to spend more time building them up than I would have expected to :roll: So I am looking to have the bulk of them assembled in China this time as there is just no way I will have time this year to start a another batch.

One of the main problems is the tolerances on the switch mode chips seem to vary quite a lot from one batch to another. So it upsets the output voltage of the 5 V rail. I do not want to produce a power supply where I will end up having to change the bias resistors on a lot of them as it will again take a lot of time up. Plus I don't know until they are built if the voltage will be "out" more than I would ordinarily like.

So I have moved to version 3.2 there I have placed a trimmer preset so the 50 can be adjusted about +\- 0.5V . I did not really want to do this originally because of the pot being noisy over time etc I just wanted a fixed resistor. Though it is really turned out to be a necessary evil unfortunately.

So I have gone for a quality branded fully enclosed trimmer but only use it as a "in parallel" with the fixed resistor. So the effect of the trimmer resistor on the feedback network is as minimal as possible.

I prototyped this just and it works really well.. So now I am currently tweaking the PCB to have this built on.

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Another side effect of this is it adds additional cost onto the power supply in parts and assembly. Mostly I was trying to keep the parts count as low as possible as they take a incredibly long time to assemble with so many different parts. With me looking to get a batch made, the number of parts does not really affect my workload as someone else can do it all instead :lol:

Next problem is nowhere has the power supply chips in stock at all :( there is over a year wait for them. BUT looking through my parts box for power supplies I found 140 of each *phew*. Though really I need more chips to get a larger batch done. So look around my usual surplus outlets to try and find a source for them. Though I have a feeling because of parts shortages the price may be a lot higher than they have been previously, which again will add cost to the power supply :(

I am trying to find a cheaper source for the large inductors currently as it would cost over a grand in those parts alone :( I do have a stock of around 50 transformers thankfully, though I need to find a cheaper source for them as they are around £15 each from Rapid :( I am starting to get back some better quotations so at least that is a start.

Overall I'm trying to find cheaper sources for the components to offset the additional costs that will be present in this next batch. Mostly I was assembling them myself to keep the costs down. Though having to pay even China for assembly would likely add somewhere between £5-£10 more per PSU. Then once I get the boards I have to take them to a friends house and pay him to assemble the transformers and test them. I know people sometimes complain about the high price of these power supplies, but I am making virtually nothing on them at the moment as they are just incredibly expensive to build ( and time-consuming). So the price rise is just unfortunately inevitable and the only alternative is to just stop making them, which I really do not want to do. I will however try and get as many of these boards as possible made up in China as I can to try and keep the costs down overall.

EDIT:

Well the switchmode chips have gone up in price by x30 because of likely parts shortages :( At the current market prices my power supplies would go up about £30 just to obtain those chips alone :roll: :cry:
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
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Re: exxos blog - random goings on

Post by exxos »

My new template seems to work well with the only problem it is actually difficult to lift it off without knocking the chips :roll:

Does anyone know of the reflow glue ? I have had a quick look around and they seem to be need to be heated to cure, which defeats the object of sticking things down before the thing is heated up :roll:

I have been wondering of just having a tiny bit of superglue underneath to see if that would do it.

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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
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Re: exxos blog - random goings on

Post by PeckPeekPoke »

It's obvious you are very busy. There must be some way to enlist some Atarians eager to help. We are legion, we are global, dispersed through nations with various resources that can be leveraged advantageously. Logistics is the key. Cost is always important, a vital metric of efficiency, but at this point Atari accessories are a boutique product for which enthusiasts are willing to pay for top-quality. The cheap-skates have already gone over to the made-in-china compatibles long ago. Certainly it would be a shame to to see your fine PSUs with the proud "Made in Britain" sticker switched to "Made in China." I would shed a tear, that might short something out. Please consider expansion and/or delegation. :cheers:
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