Smokes your problems, coughs fresh air.

Author: halfgaar (Page 2 of 26)

Halfgaar is Wiebe. Wiebe is a contributing author on this weblog. He also has a lot of stuff (such as long, in-depth articles) on his personal website.

Wiebe works at YTEC, where he is a senior developer of customer-specific tailor-made software ("klantspecifieke maatwerk software") for clients in a few select markets: wholesale, printing and healthcare.

Git and Tig config base

Here’s just a quick .gitconfig:

[core]
        commentchar = %
[tig "color"]
        date = cyan black bold
        diff-header = cyan black
[tig]
        ignore-case = yes

The colors are to make it readable on Windows Git Bash, because the dark blue is impossible to read.

And yes, I still have to set up my dotfiles github stuff.

Attempt to repair short on motherbord

At work, we had a small embedded PC that had a short in the mainboard. I attempted a fix, mostly for educational purposes. It wasn’t successful, but I wanted to post the method and result anyway. The method I used is elaborately explained on Youtube, so go hunt there for more details.

First I wanted to find the short. I opted for the method of connecting a current limited power supply and slowly cranking up the current till I can feel something heating up. To do so, I had to solder some wires to the input power jack first.

I set the supply to 1V and and started increasing the current. Given that small resistors have a rating of 250 mW, a 0.25 to 0.5 amps, giving 0.25 to 0.5 W, should be safe enough to gently heat up the shorted component. In the end, I had to increase the current to about 1.5 amps to detect a rising temperature.

I removed the cap in question:

Then I replaced it with hack (because I had no SMD parts here):

The short was gone, but it still didn’t power up. Then I gave up.

Nginx maintenance page

Just some example code for an nginx maintenance page:

server {
  listen 80;
  listen 443 ssl;
  server_name www.example.com;
 
  ssl_certificate_key /etc/ssl/temp/wildcard.example.com.key;
  ssl_certificate /etc/ssl/temp/wildcard.example.com.fullchainchain.crt;
 
  location = /503.html {
      root /srv/http/maintenance/;
  }
  location = /logo.png {
      root /srv/http/maintenance/;
  }
   
  location / {
      if ($remote_addr != 1.2.3.4) {
        error_page 503 /503.html;
        return 503;
      }
  }
}

Softstarter (ballast start) relay charred after years of use

This is an interesting case. I made a sound system for a friend in 2012. In it is a soft-starter, that engages the heavy transformer through a ballast, so that the fuse doesn’t trip. This is it:

Up until today, I never knew he had to replace the fuse a few times a year. The reason I found out now, is because the amp wouldn’t start anymore; it would always blow a fuse. So, I was called in to repair.

This is the relay now, with charred contacts:

One initial thought of course is that the amp was turned off/on super quick, so the relay didn’t have time to disengage, subsequently connecting the mains directly to the unstabilized transformer. However, my softstarter design can handle quick off-on (although not super quick, I just tested), and he was adamant that it often happened after hours of off-time, and being careful not to bounce the switch.

My theory is that the mains AC sometimes arced over the relay on turn-on, so that the ballast would be bypassed, obviously blowing a fuse. This arcing slowly wore out the contacts, and probably made it more susceptible, ultimately resulting in always arcing. However, I use the exact same design in my own builds, and I never have this problem.

The relay is rated for 250 Vac, 30 Vdc. But perhaps with the mains in the right position, the transformer acts as a fly-back.

Interestingly, the relay contacts still read near-zero Ohms, and there is little to no voltage over it with when I test it with my 30V, 3A bench supply.

I now replaced it with a nifty relay (Amplimo LRZ) that has a wider gap, and tungsten pre-contact:

I’ll report back in a year how it held up.

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