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I found out why my Nokta Legend broke

B

belaz

New member
I found out why my Nokta Legend broke. When I inserted the headphone adapter, it turned off and did not turn on again. An autopsy showed a short circuit in the stm32f765 controller. I copied part of the circuit and found out that the leg of the headphone jack. It goes through resistor r73 (1k), directly to the 97th leg of the controller. There is no protection against static voltage. You can’t do this, I don’t know why the Nokta engineers acted so badly.
1.jpg
 
I ran headphone adapters on my legend for the first few months before I started using the Avantree wireless and had no issues. I had a couple of different adapters but they were both from Nokta . Was you adapter from them or another manufacturer?
 
The adapter is original from the Nokta kit.
According to all the rules, on long lines, to protect the ports, you need to install either 2 diodes or one zener diode.
Nokta hoped that the adapter connected this port to GND. But in order for this to happen reliably, the GND pin in the connector had to be made longer. So that it is guaranteed to connect first.
This is roughly what the protection should be like (which is not available in Nokta):
io-protection-with-steering-diodes-to-rail.png
io-protection-with-tvs-diode.png
 
Totally Greek to me , all I know is I plugged in the adapters on numerous occasions for several months and never has an issue. I'm sure Nokta would appreciate a conversation with a technical person that understands the nuances of electrical engineering. I'm much more competent at building stairways and fireplace mantles
 
Why did you open it up and void the warranty? Did you notify Nokta before you disassembled the detector and posted on this forum? You did wear a static bracelet when you touched the board, right? Static electricity from a person's hand can destroy electronics without this protection.
 
belaz said:
I have been friends with a soldering iron for 30 years. I have been working in the field of electronics repair/development for 24 years. I couldn't resist disassembling this device after it broke.
Click to expand...
I'm an EE and between work and projecting over my 20 year career I have never seen or caused an ESD damaged part, and I rarely bother with "proper" grounding. Can ESD damaged surface mount electronics? Sure. Will it? Almost certainly not.
 
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