RD DPS5005 died of ESD - Page 1
Forum section: electronics / repair

author: gr84u
author_rank: Newbie
timestamp: December 20, 2019, 11:14:13 pm
content: Yesterday, after more than two and a half years of faithful service, my desk-bench power supply based on a DPS5005 and 24V switching power supply died in the line of dutyfrom a friendly fire at the moment I touched the rotary encoder (there was a electrostatic discharge from me).I wonder if anyone had similar experience with this devices. Is it worth trying to repair it? DPS5005 seems to be completely dead (black screen). The 24V power supply is OK. Any experience with such situation?

author: TheMG
author_rank: Frequent Contributor
timestamp: December 20, 2019, 11:40:39 pm
content: First thing to check would be to see if the microcontroller is getting power. Also, rule out if it's just the display by trying to enable the power supply as you normally would.If the microcontroller is dead, it's probably not worth repairing as you would not only need a replacement micro, but also the firmware and a chip programmer to be able to load it.Since it died from zapping the encoder it's most likely that the microcontroller is dead unfortunately.Is the metal part of the encoder electrically connected to the ground reference of the power supply on the PCB or is it just left floating? It should always be connected to GND to provide a discharge path for ESD on the shaft of the encoder, especially since the encoder is not mounted to a metal case.

author: gr84u
author_rank: Newbie
timestamp: December 21, 2019, 12:25:41 am
content: Thank you for the replay. Everything you have written sounds reasonable (actually I had the same thoughts, seeking confirmation).It was not grounded, and I wonder how would it be, as the rotary encoder has a knob that is metal on the outside but is isolated (plastic fitting) from the shaft.Although there is an open source replacement firmware for these deviceshttps://johan.kanflo.com/upgrading-your-dps5005/, replacing a SMD micro-controller (STM32F100) that is on a sandwich PCB design would probably be too much for me.

author: TheMG
author_rank: Frequent Contributor
timestamp: December 21, 2019, 07:01:00 am
content: The knob itself doesn't really matter but the shaft and body of the encoder itself should be connected to circuit ground on the PCB, via the solder pads which hold the body of the encoder mechanically to the circuit board. If it is not connected to anything (solder pads not electrically connected anywhere), then you can end up with ESD "jumping" from the shaft to the microcontroller I/O pins.

author: gr84u
author_rank: Newbie
timestamp: December 21, 2019, 10:06:41 am
content: The whole device (DC to DC convertor) is in plastic casing that has connector for 4 wires: In+, In-, Out+, Out-. The knob itself is electrically insulated from the rotary encoder metal shaft by a plastic fitting (that did not help much in my case). No other connections (like ground or casing) are provided. It seems that the chassis of the encoder is not connected to anything on the board. It is impossible to trace the lids as the device is organized on 2 double layer (I believe) boards in a sandwich configuration less than 5mm apart connected by 16 solder points and the screen is on yet another board on top. This would be very hard to dismantle. Rest in peace DPS5005.