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Forum Index : Microcontroller and PC projects : Ready to run PicoMiteVGA for GBP25 - good price?
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| lizby Guru  Joined: 17/05/2016 Location: United StatesPosts: 3150 |
Is that for 5 populated boards or for 2 populated and 3 bare? In either case, I've paid more than that for far less capable boards. ~ Edited 2023-05-01 23:01 by lizby PicoMite, Armmite F4, SensorKits, MMBasic Hardware, Games, etc. on fruitoftheshed |
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| George H Newbie  Joined: 03/07/2020 Location: United StatesPosts: 24 |
Lizby, that was 5 fully populated boards. In purple, of course  |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 3803 |
Should there be a circuit diagram showing the DAC? I guessed it would be in PicoMiteVGAV1.1.zip but seems not. John |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 3803 |
I'd love to see an updated schematic. I thought I might get it from EasyEDA, so I tried to import PicoMiteVGAV1.1.eprj into EasyEDA but it does not appear to recognise it as a valid project. Should it just open as an EasyEDA project? Also, is the code to support the DAC on github yet? John |
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| matherp Guru Joined: 11/12/2012 Location: United KingdomPosts: 9128 |
Here is the schematic but AFAIK the eprj file should be all you need e9bacb11-315a-4a69-8ca1-5e76f24ad995.pdf |
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Grogster Admin Group  Joined: 31/12/2012 Location: New ZealandPosts: 9308 |
I missed any/all talk about the DAC support. Can someone link me to the thread about that feature so I can read about it some more? Otherwise, an excellent looking board, and I might offer these for sale.  Smoke makes things work. When the smoke gets out, it stops! |
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| paceman Guru Joined: 07/10/2011 Location: AustraliaPosts: 1329 |
Start here Grogster. Greg |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9308 |
Thank you very much. Smoke makes things work. When the smoke gets out, it stops! |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 3803 |
Thanks. I was only trying to use the eprj to get the schematic, so no worries. John |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 3803 |
Aha! Thanks. John |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 3803 |
Just received my boards. 4 are OK (on very trivial testing). They draw a tiny current (some mA). The 5th draws >1A !! (With nothing connected except the USB to provide power.) The CPU chip is quite warm, though I didn't leave it connected for long to see what its max temp might be. I haven't wanted to connect it to my PC as I see little point until I fix it... but how do I go about that please? (I have a multimeter but that's about it. To measure volts & amps thus far I've used one of those little USB display devices which show both.) John |
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| matherp Guru Joined: 11/12/2012 Location: United KingdomPosts: 9128 |
Unless you know how to do SMD rework I wouldn't do anything but complain to JLC and request a partial refund |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 3803 |
OK - thanks. John |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 4247 |
Peters suggestion is the only option unless you are into smd repair. If you are curios, sometimes visial inspection reveals the culprit. Short between pins, not soldered pad, tombstoning, chip orientation wrong, wrong component placed. Since you have 4 that work, you have reference... I would be curious... Volhout PicomiteVGA PETSCII ROBOTS |
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Quazee137 Guru Joined: 07/08/2016 Location: United StatesPosts: 571 |
Like Volhout said do a/b and get a pic of the problem. Send it to them just may be they'll send a 2nd set. Had that happen with just the PCB's they sent a 2nd set to me. They are good at support. Quazee137 |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 3803 |
Thanks. I'm not terribly bothered - they're great value anyway. SMD stuff is waaayyyy beyond me, but a good look under a strong light I can try. I don't need a 5th board (not sure how many I _need_ LOL). John |
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Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6798 |
Let them know anyway. It's a QC thing and they may have a problem with components or something. They'll appreciate it. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 3803 |
Will they? OK. I'm surprised it draws so much current but doesn't seem to be a short. Well, not of the USB 5V to Gnd, I suppose a short further from there will have some resistance between power in & the problem. I had a look with a magnifying loupe-type thing and can't see any solder bridges or whiskers. If you really think they'll want to know I'll contact them. John |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6798 |
I doubt if they run tests on the assembled boards, that would be too specialised. They do on the bare PCBs, but that's flying probe point to point stuff, I think. If an assembled board is out of spec then there's either a short or a bad component somewhere. The boards are, as far as I know, machine assembled (maybe not the through hole components) so I doubt if its a short. That only leaves a bad component - which they supplied. Have you done a visual comparison with a good board to see if the right values are in the right places? Also, check that there is 3V3 coming from the regulator (usually the middle pin). A hot chip could mean that the regulator is short circuit, wrong voltage, or isn't a regulator at all! Edited 2023-05-15 22:14 by Mixtel90 Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 3803 |
It looks plausible (components etc). Centre pin of the 3V3 regulator is 1.2-1.3V unlike the other boards which are 3.3V Outer pins are OK. I found a place on the bad board which is not like (ohms) a good board. Measuring from the 3V3 supply rail to a contact of C13 looks unconnected on good board but 2R5 on the bad one. I see C13 on the schematic but I'm not much the wiser! (I get the same 2R5 on some of the vias on the bad board rear, too.) Unless you're wanting more tests I'm happy to junk the board. John Edited 2023-05-17 02:21 by JohnS |
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