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lizby
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Joined: 17/05/2016
Location: United States
Posts: 3841

Posted: 11:51am 03 Aug 2026

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romba6 said showing no stock for the raspberry IC and one other component

The German group order people had gotten some indication that the parts would become available sometime in August. Might be worthwhile to check again later.

~
Edited 2026-08-03 21:53 by lizby

PicoMite, Armmite F4, SensorKits, MMBasic Hardware, Games, etc. on FOTS

JohnS
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Joined: 18/11/2011
Location: United Kingdom
Posts: 4361

Posted: 12:50pm 03 Aug 2026

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romba6 said

JohnS said Anyone in the UK selling/ordering built Pico Computer 3 boards?

John

I was thinking of it and went to JLPCB to place an order this a.m and got as far as the BoM and they are showing no stock for the raspberry IC and one other component. I gave up as with my eyes and hands I wouldn't be able to fit my own.

Thanks.

(I can't find them, either.)

Let me know if things change and you're able to order some built ones, please.

John

matherp
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Joined: 11/12/2012
Location: United Kingdom
Posts: 11701

Posted: 03:22pm 03 Aug 2026

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I've found a fault on the current PC3 design files (all boards so far made). This causes the ch334 hub chip to get hot, particularly if the programming cable and usb-c are both left plugged in and even when the switch is set to hub. Some time ago I swapped versions of the CH334 chip to use the CH334U as the previous variant had a bad batch at JLC.
What I hadn't understood is that this variant has an internal 3.3V regulator. It has two pins 20 and 21 marked 3.3V and 5V on the datasheet so that is how I connected them. What this means is that if the regulator in the CH334U is producing a higher voltage than the LM117 then the hub chip is trying to power the whole board and hence getting hot.
The correct wiring is either 3.3V on both the 3.3 and 5V pins, or 3.3V pin bypassed to gnd with 0.1 and 10uF caps. In addition R92 currently pulls up to 5V (only 10K so not serious) whereas it should pull up to 3.3V although there is an internal pullup so it is not really needed at all.
If the board isn't giving any issues then you can leave it as-is. If the ch334U is getting hot then you can mod the board as follows:
Cut the 5V trace to pin 20 between C67 and the pin. Short pins 20 and 21. Remove R92.
I will post revised gerbers shortly.

matherp
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Joined: 11/12/2012
Location: United Kingdom
Posts: 11701

Posted: 04:11pm 03 Aug 2026

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Updated design files now on https://github.com/UKTailwind/Pico-Computer-3/releases
Edited 2026-08-04 02:11 by matherp

Bryan1

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Joined: 22/02/2006
Location: Australia
Posts: 2188

Posted: 10:18pm 03 Aug 2026

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The steps I use turn off the switch for the hub insert the programming USB cable holding down the reset button then program the board, once the prompt on the computer goes away take out the programming USB cable insert the C-USB then power it up.

So at NO time are both USB cables are on the board.

By the way Peter I'm running V0.12 of the micro-python is this the latest version?

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