25
votes
Accepted
Do LEDs require more power to function as they age?
The problem you are seeing is related to the construction of LED backlight circuits which require lots of LEDs. Often on poorly designed or "cheapo" designs there are LEDs or series strings of LEDs ...
- 57.9k
12
votes
Accepted
Why do large PCB traces have solder points/islands/stripes on them?
Probably an attempt to reduce the resistance of the trace (and better dissipate heat) by putting solder in parallel.
The pattern in the solder mask is likely so that a solid section of solder does ...
12
votes
Why do LCD screens need to refresh in the first place?
Some modern LCDs (especially ones built into phones and laptops) do kind of work this way; it's called "panel self refresh", which means that the display has its own memory that stores the ...
- 8,227
10
votes
Do LEDs require more power to function as they age?
Yes, even LEDs do not have an infinite lifetime.
However, when run at a low enough power such that they do not heat up much a lifetime of 50000 hours can be expected. 50000 hours when operated 24 ...
- 81.4k
10
votes
Accepted
Why multiple series resistor on single phase metering reference design with HLW8012 and BL0937 IC
The main reason is the voltage rating of the resistor. Finding a 1.2MOhm resistor in ,say, 0.25W with a voltage rating of 600V or so is more difficult or expensive than using a string of common garden ...
- 6,678
9
votes
Why did a spark occur between my HDMI cable and metal lamp base?
If everything had been working previously in some configuration with the HDMI cable plugged in at both ends then my best guess is that there is a fault in your lamp. Maybe an earth has become detached ...
- 2,512
8
votes
Why do LCD screens need to refresh in the first place?
The whole reason is the component circled in red below (Cs) which is a capacitor. Capacitors are really easy to manufacture, you only need two conductors and to space them apart with an insulator or ...
- 88.8k
7
votes
What advantages do CRTs still have over more modern display technologies?
CRT displays have several advantages over more modern technologies:
Minimal response time, as incoming pixel data is generally beamed to the screen immediately as received, with virtually no ...
- 8,681
7
votes
Are all pixels addressed simultaneously in one frame?
There are different technologies used for "computer screens".
Today's most common technology is TFT-LCD which mostly uses the Active Matrix adressing scheme to build up an image.
... is ...
- 81.4k
6
votes
Why did a spark occur between my HDMI cable and metal lamp base?
If you aren't in the US, ignore this answer. Also, be very careful with live outlets.
The problem could be a miswired plug. You can buy an outlet tester for a few bucks at a hardware store. They light ...
- 351
6
votes
CRT vertical deflection problem
If this problem has remained after doing all the usual checks (for dried out electro caps, aged variable resistors, bad solder joints) and after the power supply rails have all been confirmed as being ...
- 5,865
5
votes
Monitor displaying negative colours
One possible mistake would be to get one of the the (optical) polarizers backwards if it's not bonded to the LCD glass, the polarizers are usually done at 45 degrees so that the manufacturers can use ...
- 36.4k
5
votes
Spoofing or hiding monitor serial number
Ok, we'll need to clear up a few things:
A MAC address of a computer can be spoofed by an FPGA which can be programmed as a network controller.
Um, yes. But any modern (think: the last 20 years "...
- 100k
5
votes
Old monitor’s internal power supply works only when heated from the outside...fixable?
I see at least two things:
First is the capacitor that's already been pointed out to you.
That's this one:
It can cause many kinds of problems. It needs to be replaced, no matter what else may ...
- 73.6k
5
votes
Accepted
Why do LCD screens need to refresh in the first place?
(Other aspects are already explained well by other answers. This is just a note for the curious).
You might be interested that LCD displays like this already exist. (See this "Memory LCD" ...
- 1,604
4
votes
How to figure out what DC power jack I need?
I would guess it's a 2.5mm DC power jack, but it could be 2mm. Both come in varying shapes and mounting styles, so either way you'll have to take some measurements to know for sure.
I think the ...
- 4,057
4
votes
Accepted
How to figure out what DC power jack I need?
The commonly accepted name of this part is "barrel jack". The power jacks come in variety of sizes, often characterized by pin diameter (Inner Diameter), and OD (outer size). This particular ...
- 42.4k
4
votes
Accepted
What advantages do CRTs still have over more modern display technologies?
The display is much smoother on an analogue oscilloscope. You have to pay a lot for a graduated digital display that can produce as perfect a sine wave as :-
If you get something like a used Hameg, ...
- 7,621
4
votes
How can I convert a VGA signal to work with an old CRT monitor
From the nomenclature describing its inputs, and the ancient jack, and having a CRT display, am guessing that this accepts video from long ago. Long ago, video with NTSC timing format was very common. ...
- 27.6k
4
votes
Accepted
Do cold cathode fluorescent lights (CCFLs) degrade as a function of idle time?
Probably the ~10k hours of actual use. According to this article in Appliance Design a typical CCFL at room temperature will be down more than 20% after 10K hours at room temperature. Of course ...
4
votes
How do LCD screens repair themselves?
How do LCD screens repair themselves?
I pushed down on it too hard (actually wasn't hard at all, to be honest). Anyway, next time I turned it on there was a huge blob of dead pixels in and above that ...
- 281
4
votes
Accepted
Use different adapter for LG 25UM65-p
While the current available @ 2.14A is high enough - the voltage at 14v will be too low and it will likely not work.
If connected correctly it is unlikely (but still possible) to cause damage though ...
- 356
4
votes
Why did a spark occur between my HDMI cable and metal lamp base?
The crater shows enough energy was released to vaporize metal. This means the usual causes of small sparks and shocks, like line filter capacitors, are not involved here. This looks like what happens ...
- 81.7k
4
votes
Accepted
Why is the power adapter external (not built in) to the monitor?
I can see a few reasons why the manufacturer might have decided to use an external power supply :
easier certification : certification for a product with hazardous voltages (ie mains) is "...
- 8,118
3
votes
Accepted
A novice question about 60Hz vs 50Hz frequencies in monitors
It is the screen refresh rate (approximately!).
A little history: Way back in the day when the CRT telly was a new and shiny thing, capacitors were expensive and voltage regulators were very ...
- 17.6k
3
votes
Accepted
EGA display converting to VGA - screen's shaking
The GBS8200 upscaler chip runs on 3.3V and doesn't like 5V TTL inputs. Typical symptoms of excessive input voltage are vertical shaking and intermittent freezing of the display.
The GBS8200's ...
- 57k
3
votes
Wiring a 3.5mm Audio out jack where Speakers were previously
You are assuming the speakers are driven with single phase and ground. That may be a BAD assumption. The speakers may be driven in push-pull mode.
See this cross post.
Try connecting ONLY the L, and ...
- 47k
3
votes
How does Mains Isolation work with the ACS71020 IC?
The multiple 1 MΩ resistors are part of the isolation barrier between the mains and the low-voltage side of the chip. Clearance and creepage are not an issue at the pins, because the chip itself ...
- 178k
3
votes
Accepted
Calculating Energy Consumption Using a Current Sensor and Voltage Sensor
I'm creating a PCBA that uses a hall-effect sensor to measure current
and a transformer rectifier design to measure the mains voltage.
And
But I seem to be getting errors in my Wh calculation
...
- 473k
Only top scored, non community-wiki answers of a minimum length are eligible