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EEVblog #1107 - Shocking 4K BENQ Monitor Problem!

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Why does this 4K BENQ monitor mysteriously switch off on it's own?
Inadvertently re-visiting an old video.
The chair strikes back!


--- Quote from: EEVblog on July 20, 2018, 12:18:03 am ---Why does this 4K BENQ monitor mysteriously switch off on it's own?

--- End quote ---
Most likely because of the crappy video cable. It's not switching off, it just blacks out because of the received data corruption. Seen this crap myself with 3rd party cable which had the shield but it wasn't connected to anything.

It just dawned on me that this may be the problem with a Eizo monitor I have at my workplace. It switches off and on seemingly random, worse on some days and other days not at all.
I resolved the issue by switching to display port instead of DVI.

I actually had this problem at work, I've just finished a graduate traineeship with ESA (I was making a digitally controlled Buck + Boost Converter). I was having some serious issues with it, working one minute and stopping the next. The main issue was that each time this (at that point) unknown issue occurred, it would blow the arse out of my high side and low side FETs on the buck side - direct short between G-D-S, all three!

Of course, after about 5 days of no luck, testing everything I could think of, I was beginning to get quite disappointed. So, staying late one Friday night, I thought I had solved the issue - it had been running fine (in open loop conditions) and no failures. A failure was quite obvious to see since the power supplies would go in to over current protection.

"Excellent! Time to grab a coffee and leave it for a while to see if the problems solved". So, I stood up, and heard the devastating click of the relays in the PSU going into short circuit protection. At this point, it seemed far to coincidental.

I remembered, from a couple of years ago, watching the video Dave made on this phenomenon back when I was at university (probably in my first year!). I didn't have (and still don't unfortunately!) a scope of my own, so didn't get around to testing it. However, that Friday night I realised what a pain in the arse ESD was. I re-soldered two new FETs (DPAKS, so a total pain to unsolder and resolder 15+ times) and stood up from my chair again, this time probing the gates of the MOSFETs (possible making the injection worse?). And sure enough, it failed again, with some horrific interference (if anyone's interested I have some scope shots somewhere)

So, thanks a lot Dave! No one believed me, even engineers with 30+ years couldn't see how my chair was causing my converter to fail. I explained I watch your video a few years ago and tried it out, showed them, and after they checked all my grounding/PCB layout/etc, they agreed it was the chair!

In the next few says I brought in one of those lights with the piezo crystal starters that was empty of gas. It was a lot more convenient to troubleshoot the issue than standing up and down from my chair all day! Interestingly, this problem only showed itself when the weather changed and it got more dry. (BTW: Sitting on an ESD mat was my solution for a while, but I like the cardboard box idea too!)

joseph nicholas:
I took apart a bad quality vga cable from China and cut the chock apart to find it was , well there was no chock at all in the plastic cast, on both ends.


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