Unfortunately it is difficult to assess how every / any specific PSU will perform. The symptoms described do point at a lack of power. There are several contributing factors:
PSU - should be good quality able to provide 3A or more. Some PSU have ratings that are not accurate, i.e. they supply less than the stated current or are inconsistent, collapsing occasionally.
Cable - a low quality cable can lead to high impendence which in turn results in voltage drop across the cable. This will mean less than the required 5V at the Raspberry Pi. In general a good quality cable will be flexible but fairly thick. A stiff cable is likely to be single strand conductor wire which has poorer performance and a thin cable indicates smaller conductor cross-section which equates to higher impedance and hence more voltage drop.
Good connectors - the connector on the cable should mate well with the socket with no lateral movement, i.e. it should fit snugly and securely with a positive insertion action. It should not be tarnished and its conductor pins should make good contact. If the PSU has a socket (not captive cable) then both plugs need to be sufficient quality.
Physical debris - it is possible for debris to sit on the Raspberry Pi which might cause electrical bridges between conductors. These could be tiny with small impact but enough to degrade performance. Similarly debris could build up inside connectors causing bridging, insulation and mechanical blockage (connector not pushing home fully).
Faulty PSU - electronic devices have a chance of failure and occasionally may give suboptimal performance even when new. This risk increases when devices are sourced from less reputable or trusted suppliers.
There are many different PSU in use across the community, many having similar physical appearance but maybe with quite different performance. @jofemodo has experimented with some PSU and found some to be acceptable but the common advice is that the official Raspberry Pi PSU continues to be a good choice and is the recommended unit for Zynthian. It provides the required current with good quality captive cable and is available in most regions at a fair price. Poor supply is probably the most common cause of issue reported for the Zynthian and diagnosis can prove challenging because behaviour may be inconsistent and the PSU specs might sound fine.
If you add a switch you could undermine the effectiveness of the PSU. Indeed, a switch will add impedance to the supply and may be inconsistent due to tarnishing of the contacts.
If you want an ON button and are handy with a drill and crimp tool you could add a push-to-make button between pin 5 and ground , e.g. pin 6. When Raspberry Pi is off the hardware listens on pin 5 and powers up if it detects a low pulse. Be aware that pin 5 is used for I2C communication so pressing the button during operation will interfere with the physical UI. This also makes it challenging to add the button to the header. Maybe @jofemodo may consider adding a button to a future version of Zynthian.
Keep in mind the Zynth is a full blown computer, and computers dont enjoy just having their power yeeted away. Theres always a chance that if the OS is doing something funky with the filesystem you could end up with a corrupted SD-Card. Granted modern OS’s usually use a journaled FS so that mitigates the damage a little bit, its not completely immune either. If your going to have a power off, have something that listens to a button and then initiates a proper operating system shut down.
Robert M. Pirsig’s novels; “Zen and the Art of Motorcycle Maintenance” and “Lila: An Inquiry into Morals” explored the metaphysics" of quality. I can’t recommend these reads highly enough if you want a simple introduction to philosophy. Lila was a bit more challenging! Maybe I digress even more than @wyleu does on occasion but his question of the definition of quality had to be explored…
I’ve read Zen and the art of motorcycle maintenance. And it certainly did contain some interesting insight. The irrational irritation brought on by an un-fixed dripping tap sticks in the mind.
I’ve got about four zynth’s in various states of that . . .
Ive not been so lucky. I have had a couple of zynths that have never seen the light of day, but they are often recording or playing when the power goes and I tend not to use external USB sticks.
Just a 5 amp switch and silicon 20 AWG wire.
The thought process is that a higher amperage would mean lower impedance (this was an educated guess and never tested nor contrasted with actual physics)
Hello again!
I’m using an official Raspberry Pi power supply but I’m still facing the same issue: most of the times my Axiom mini USB is not accepted.
I don’t know what else to try.
Like with the previous power supply if I boot Zynthian with multi-timbral mode on it’s much more likely to have the Axiom USB properly recognized so I still have some doubts that the issue is not totally depending on power supply.
Thank you!
