I’m thinking I might just be quite unlucky with the USB fullsize-B cables I have lying around (despite their ability to power other synths I have, and some of them being fairly new), but before I go about buying yet more cables I figured I should check in and make sure that tge V5.1 kit with a Pi 5 inside is actually expected to be able to power on via USB power. It definitely works via the AC adapter I got shipped with the kit, and everything else seems fine so I don’t think I screwed up anything in my assembling of my Zynthian kit . . .
ummmm, Could there be a misunderstanding here? A 5.1 kit wants to be powered via Barrel connector next to the power switch at something like 24 to 48 volts. I’m not sure of the exact voltage but it’s not powered via a USB cable at all.
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Well that answers my question! I wasn’t sure because nothing on the wiki or store page ever lays that out unequivocally, and in several places it’s mentioned that one should get a good USB power supply—if not for those mentions I would have just assumed it needed the barrel plug power and wouldn’t have been eying up the fullsize B port right beside it 
OK, good. I’m unaware of the mentions, if you point them out we can see if they’re misleading.
Hi @keithzg!
Welcome to the gang. Before V5, zynthian used the naitive Raspberry Pi power connector which is presented as a micro USB on RPi 3 & 4. This is where it was essential to have a good PSU with good cable. V5 adds a power circuit that takes the barrel connector PSU and converts to the required voltage rails. I don’t have access to the circuit design here (it is in github but needs kicad to view which I can’t get to right now) so I can’t confirm whether it is possible to bus power the V5 but I suspect not. @jofemodo can answer that.
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Hi @keithzg !
No. You can’t power the V5 using the USB-type B connector or any other USB connector exposed in the alucase’s back side. You MUST use the barrel connector to power the V5 mainboard. There is no other way.
FYI, USB type-B connectors are under-rated and can’t manage the amount of current needed to power the V5 (2A to 5A @ 5V). So we decided to disallow this possibility to avoid bad UX. Indeed, there is a diode in the mainboard that avoids to power from the USB type-B connector.
Regards,
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Hi .
The Zynthian V5.1 could be powered by a “USB-C trigger cable” (search term) from a USB-C power supply.
The same trigger cable can power the Zynthian from a USB-C power bank that can deliver 65W power. Types with lesser power rating are unlikely to work, as their makers usually brag about product capabilitie and exaggerate largely.