snipe3687 wrote on 2024-11-23, 21:27:
Shreddoc wrote on 2024-11-14, 21:54:
Over the years, the majority of issues observed with PicoGUS self-builds has turned out to involve careful attention to U2/U3/U4. Even people with the skill + experience still have a tendency to rush it, and miss a small detail at first. I know I have, on more than one occasion.
Interesting, could you elaborate on that? I originally built 5 of them and only 1 actually worked. the others had various issues. some I could flash them but couldn't get them to detect, some would detect but then would play garbled audio or crash the system and 1 worked fine but would crash in GUS mode. these were the chip down version. I built 5 of the module versions too and they were totally fine. you said U2-U4 specifically. what about those chips do you feel are problematic for self-installers? I'm always looking at ways to better my skills and I'd love to sort the other cards out at some point!
Take my comments as the opinions of a fellow amateur solderer, I'm no senior authority on the science. I've handmade about 25 x PicoGUS 1.x's over the past 2-3 years (time flies!). It sounds a lot but probably averages out to mere minutes per day. If I was spending even 1 consistent hour per day doing this, then it would different.*
But this is not my day job, so as a hobbyist, imperfections happen. At least 20 of those 25 builds required little fixes here and there, upon inspection after first attempt. Those fixes almost always included some aspect of U2/U3/U4/DAC, because those IC's are the smallest in pitch and have many pins clustered together.
The build experiences that others have posted in this thread over time seem to have mirrored that pattern (or so my vague meat-memory record says). And a proportion of those experiences involve surprise that it happened to them. That's no aspersion, it's just how it goes. For me too.
On a technical basis, there's the sheer size/pitch. But there are also other factors and perils. The providence of the parts (i.e. consistent quality providers). Technique. The flux and solder quantity and quality and temperature. The tip used. How much of a hurry the operator is in. The IC legs. The pads themselves. Damage inadvertently done during the course of multiple rework attempts is its own minefield. Read the last sentence again, because it's bitten me a few times. And of course, the classic bridges, which can come in all shapes, sizes and positions, from big obvious ones, to the occasional one so incredibly cunningly hidden that you can only award it a wry grin of acknowledgement when you finally spot it after desperately renting an electron microscope at $5000/hour (eliminate slight exaggeration at your discretion).
*There's a great variance in the equipment and consumables people use, too. It's no coincidence that quite a few people approach the PicoGUS and similar great open source hardware builds as learning experiences. That often means entry level equipment.
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P.S. Regarding the Integrated-DAC version of the 1.2 - the DAC IC in particular is a step-up in technical challenge, from the DAC Module version. Simply because it's not only at TSSOP scale, but it's also closely surrounded by a cavalcade of 0805's. Accordingly, I've found it a very good idea to solder the DAC chip relatively early in the build, and give it it's full microscopic inspection, continuity test, and rework prior to surrounding it.
Supporter of PicoGUS, PicoMEM, mt32-pi, WavetablePi, Throttle Blaster, Voltage Blaster, GBS-Control, GP2040-CE, RetroNAS.