Re: LENOVO THINKPAD T450 NM-A251 schematics
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Re: Replacing Mode Indicator LEDs
Okay I thought there must be something else other than just an LED going on, so I hooked up directly to the voltage this time.
I'm gonna just buy a few different 14V through hole LEDs with built in resistor, see which performs closest to this and use it. I will just use the one colour and put labels beside each LED....Last edited by VitalComputing; 09-19-2023, 03:37 PM.
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Re: Replacing Mode Indicator LEDs
Okay I carried out a little experiment with the one LED that is still fully intact. I measured the 500 ohm resistor and it is actually 462 ohm to be exact. I started at 10V and worked my way up to 22V.
Any opinions would be welcome....
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Re: Replacing Mode Indicator LEDs
I set it up originally with a 9V battery and 500 Ohm resistor, and tested with a spare LED and it worked fine - 2.6V drop across LED, remainder dropped across resistor.
When I swopped in the indicator LED from the board, it would not light up at all, so I had to increase the voltage. Only after I put about 14V across it, did the indicator LED from the board start to light up.
I'll see if I can remove the giant heatsink to view the other side of the board....
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Replacing Mode Indicator LEDs
Hi all,
I have what should be a simple job but is causing me issues. There are three LEDs (yellow, green and red) on the indicator panel of a solar PWM controller and these have broken off. I need to replace them but I am unsure of the voltage drop across these. I don't want to replace with random LEDs in case they blow.
I took one of the LEDs out of circuit, put 19V across it with a 500 ohm resistor in series and there is a drop of about 13V across the LED, and this seems to increase as I increase the input voltage.
I thought I could just put a resistor...Last edited by VitalComputing; 09-17-2023, 05:04 PM.
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Re: Chuwi HeroBox blown components
Here is both sides of the board.
On the image below, I've marked out the two ports in that area, and with the yellow line marked the path that the input voltage appears to take, across the missing capacitor (I presume), through a small inductor, and through a fuse. I've marked the known grounds on the board also.
...
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Chuwi HeroBox blown components
Hi everyone,
I have a Chuwi HerBox that has a number of blown components that I am having difficulty identifying. No schematic available.
The fault is that the HDMI port does not really function properly, video looks shaky and has lines. The box boots fine on VGA, so I think the problem is isolated to the HDMI.
The section below is the only section that seems to have damage to three components.
1. Blue Arrow = I think this was a capacitor (as it is connected to ground) that blew clean off the board.
2. White Arrow = I think this is...Last edited by SMDFlea; 05-28-2023, 07:28 AM.
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Re: Help identifying component on main board of Acer KG281K monitor
Yeah guys, I'd say it's one or the other. I tried freezing but no go. I've put it back together and I'll keep it in stores. Hopefully the guy I bought it from knocks his second KG281K one off the table some time soon!...
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Re: Help identifying component on main board of Acer KG281K monitor
Here are all the voltages measured on the main board.
I found two shorted components on the second HDMI port (marked by the white arrows), which I removed. Was hoping that might bring it back to action but no go.
I'll try more tomorrow....Last edited by VitalComputing; 02-13-2023, 04:10 PM.
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Re: Help identifying component on main board of Acer KG281K monitor
I was in the process of marking out all the voltages on the board in Photoshop when I discovered that that section of the board had no voltage on it and started troubleshooting there. I will complete the full list of voltages across the caps and inductors on the whole board and upload later. The 3.3V is present on the button panel, so I am sure I will find it on the main board also.
I think I'm trouble with this one. Don't seem to be able to source a replacement main board either. It's listed on a site...
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Re: Help identifying component on main board of Acer KG281K monitor
Original owner said that monitor didn't work after a power outage.
When I plug the monitor in, the blue power light comes on, but nothing comes on the screen and no backlight. Even though the power light comes on, it does not turn off when I press the power button on the button panel. I've checked the button panel and there is 3.3V on all buttons, which is grounded when I press each button.
I've disconnected the main board and on PSU board jumpered the ON/OFF pin to 5V (using a resistor)...
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Re: Help identifying component on main board of Acer KG281K monitor
I've cleaned off the chip and that was just a bit of dirt above pin 3, not physically damaged like I first thought. So it does seem that the issue is with the chip not being enabled, rather than the chip being damaged.
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Re: Help identifying component on main board of Acer KG281K monitor
Below are the voltage measurements on the six pins of the IC. I can't get a reading from pin 1.
Resistance between pin 6 and ground is 0.472k ohms. I checked for shorts to ground on all IC pins and the only one that is short to ground is pin 2, which is the ground pin. I think I'll just source a replacement IC and install....
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Help identifying component on main board of Acer KG281K monitor
Hi All
This component is from the main board of an Acer monitor. I've been fighting this monitor all day and I refuse to let it beat me! Can anybody identify what this component might be?
I have 20V on the input side of the component and nothing on the capacitors on the other side of it. Does it look damaged or does this component have two markings???
thanks...
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Re: Taking Pictures Of Large Circuit Boards
Hey Sam, I guess the only thing I am missing is the text on the ICs. I will play with the lighting and see if I can get that any better. This would be one of the bigger boards that I deal with so the smaller boards should be even easier to capture.
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Re: Taking Pictures Of Large Circuit Boards
Hi guys,
I let the thread sit before responding in hope of a few more answers. I hear what you're saying about the light. A lot of guys with online channels use an anti glare light with their digital microscopes and the difference it makes is incredible.
I've been just trying a few more things with the basic iPhone 11 camera to see how good I could get it. The images are coming in at about 4MB each. I turn on the grid to make sure to get the image board square on. what you think - is it possible to improve...
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Re: Taking Pictures Of Large Circuit Boards
Hey CapLeaker, I was waiting to see if anybody else would respond but apparently not!
I downloaded that Halide app on my iPhone 11 but I'm not sure it's much better. It does have a close up mode, but I don't see enough of a difference over the iPhone camera app. Think I might be able to get a free upgrade to iphone 13 on my work phone contract, as I know that it has the new macro mode. Maybe that is the answer....
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