I had finished building the Ryde receiver and had set the PSU output for 5.1V. After about an hour the 3A fuse blew and I noticed that the voltage had gone up to 8.7V. The fault was a dry joint on the pot which adjusts the output. The RPi4 has stopped working and only a small red Led flashes constantly. Has anyone had a similar experience ? With raspberry pi's selling for £150 I wondered if it might be worth trying to repair it. Possibly it is only a voltage regulator which has blown. Any suggestions welcomed.
Gordon
Beware cheap buck PSU's
Forum rules
This forum is run by the BATC (British Amateur Television Club), it is service made freely available to all interested parties, please do not abuse this privilege.
Thank you
This forum is run by the BATC (British Amateur Television Club), it is service made freely available to all interested parties, please do not abuse this privilege.
Thank you
Re: Beware cheap buck PSU's
Hi Gordon,
Bad luck!
You probably have found this already but the link to understand the flashing sequence is here:
https://www.raspberrypi.com/documentati ... lash-codes
73,
Paul G4KZY
Bad luck!
You probably have found this already but the link to understand the flashing sequence is here:
https://www.raspberrypi.com/documentati ... lash-codes
73,
Paul G4KZY
Re: Beware cheap buck PSU's
Too late now but best to replace these pots with a pair of resistors, or add a resistor to limit the maximum voltage to 5.5V or similar. This is why there is a Zener diode used on my Ryde board. Accidents can happen.
Mike
Mike
Re: Beware cheap buck PSU's
Good Morning,
Thanks for your suggestions,I had no idea that there was a comprehensive code set for the flashing LED. I will examine it carefully just in case there is a possibility of a repair. I had wondered if a Zener might protect the RPi but whatever protection system is used,it has to work faster than the RPi destroys itself.I shall give this a lot of thought and see if I can come up with something which looks foolproof.
Gordon
Thanks for your suggestions,I had no idea that there was a comprehensive code set for the flashing LED. I will examine it carefully just in case there is a possibility of a repair. I had wondered if a Zener might protect the RPi but whatever protection system is used,it has to work faster than the RPi destroys itself.I shall give this a lot of thought and see if I can come up with something which looks foolproof.
Gordon
Re: Beware cheap buck PSU's
A Zener is fast, but won't work on it's own without a suitable fuse or other current limiting device. There are other options that would also work perhaps more efficiently for over-voltage protection.
This can also happen to linear PSUs should the series regulator go short circuit. This was a common problem back in the day, with many crowbar circuits used to protect radios from failing 2N3055s. Maybe we need to include one for the PI supply now. When the PI was £30 it wasn't such a loss but now it is often £50+, if you can get one, it makes more sense. We tend to make sure we include over-voltage protection on our shack 13.8V PSUs because of the value of the radios connected to them.
Mike
Edit - I should have said, a Zener will work in this configuration as the MP1584EN DC-DC module should go into current limiting when the Zener conducts. The limit is 4A so the Zener can't maintain this for very long, but hopefully long enough to do the job. On my GPIO boards (and also minitiouner V2) this was protection really only intended to guard against finger trouble when setting the voltage. The recommendation is to set the voltage before connecting to following circuitry, but sometimes advice gets overlooked or as in this case, another failure occurs. If you are lucky, the Zener will fail short circuit and all will be well. If you are unlucky, it won't.
This can also happen to linear PSUs should the series regulator go short circuit. This was a common problem back in the day, with many crowbar circuits used to protect radios from failing 2N3055s. Maybe we need to include one for the PI supply now. When the PI was £30 it wasn't such a loss but now it is often £50+, if you can get one, it makes more sense. We tend to make sure we include over-voltage protection on our shack 13.8V PSUs because of the value of the radios connected to them.
Mike
Edit - I should have said, a Zener will work in this configuration as the MP1584EN DC-DC module should go into current limiting when the Zener conducts. The limit is 4A so the Zener can't maintain this for very long, but hopefully long enough to do the job. On my GPIO boards (and also minitiouner V2) this was protection really only intended to guard against finger trouble when setting the voltage. The recommendation is to set the voltage before connecting to following circuitry, but sometimes advice gets overlooked or as in this case, another failure occurs. If you are lucky, the Zener will fail short circuit and all will be well. If you are unlucky, it won't.