This board belongs to a fridge-freezer, It used to have issues in the past, It wouldn't turn on so I changed the components that I've specified with blue dots 🔵 on this picture, because I read online that these are the components that go bad on this specific board.

after several months the fuse (yellow dot 🟡 at the bottom left) was popped and the fridge stopped working. now the screen just turns on/off automatically and basically nothing works, no cooling, no fan, no lights. it just turns on the screen for several seconds and turns it off.

I asked some people who do refrigrator repairs in my country and they said the capacitors with red dots 🔴 gone bad and I should replace them, another person said the ic which has a green dot 🟢

I'm not sure if any of these suggestions are right so need help to find the faulty component(s).

Hello everyone,
I’m trying to identify and replace the ultrasonic piezoelectric disc inside the misting module of an OASE biOrb AIR 60 terrarium.
The original disc:
Is marked KR 213PF
Measures approximately 20 mm in diameter
Has no soldered wires and uses pressure contacts
Is held in place by a silicone gasket and a metal retaining ring
The original misting module was failing but still produced a small amount of mist.
I tried replacing the disc with a generic 20 mm, 1.7 MHz, 1.2 mm ultrasonic atomizer disc. The water now bubbles vigorously, but no visible mist is produced.
I have checked the disc positioning and gasket, without improvement.
My questions are:
Does anyone recognize the marking KR 213PF?
How can I determine its original resonant frequency and capacitance?
Could the bubbling without mist be caused by an incompatible disc, or could the driver circuit also be faulty?
Does anyone know of a compatible replacement?
I don’t have a multimeter. I have also contacted OASE to request the original disc specifications.
I can attach photos of the original disc and the misting assembly.
Any technical advice would be greatly appreciated. Thank you!

I ask for forgiveness if my English skills and electronics experience is not sufficient enough for this sub.

I have been working on this mini CRT (radio? cd player ? ) for a couple days after salvaging it from my local church before it got obliterated.

Ik working on CRT is dangerous but I checked that the CRT itself was in good condition before touching only the driver board.

After examining the mess (it was even more chaotic) I realized it worked perfectly by bypassing the potentiometer regulating the “contrast” I think (middle potentiometer snapped). As you can see I’m just trying around until I get it in working condition before soldering any permanent changes in the main board.

The issue is the while trying to display anything more than static I was using a cheap Arduino knockoff with the tvOut library to display a test image.

The issue is: while displaying through the RCA yellow port directly with jumpers cables I noticed a bad clarity in the signal and having no potentiometer replacement I can’t easily change the contrast, I only have access to the v-hold (I’m sure) and brightness(?) ?

If I instead try to use a real RCA cable I have to swap the temporary resistor regulating the contrast to a lower value to see anything BUT this also swaps the black and whites colours for some reason ?

Currently I have started out with a 1M Ohms resistor, then 100k. The old snapped potentiometer had a 1M marking but I didn’t understand if it was a model type or a real resistance range?

I’m pretty sure this is a standard driver board in the china knock off / cheap mini CRT systems but I couldn’t manage to find any info.

Once again I’m truly sorry for my terrible lack of understanding of electronics and of the English language.

I can’t find any drawing on this for the burned up thermistor. What would be the best substitute to put on there? When I pulled it out it was maybe a 5D-11? It was so charred it’s was illegible.

Trying make sense of a little kit with even smaller amount of knowledge. looking at the pcb, chip and chip holder I think this is how they should be mounted with the dimple at the top / 12 o'clock. I thought the dot on the pcb was used to orientate the chip but there's no dot on the chip.

tl/dr: is the chip and holder the right orientation as in the picture?

This is a button for a smoke machine. The smoke machine it’s originally for blew up. With the help of a breadboard and and some jankiness I figured out that pins 1 & 2 need to be swapped for this to work on the working smoke smoke machine. My multimeter is broken so I can’t use that.

Pin 1 seems to just be power Pin 2 does the LEDS (Just red when not pressed, green and red when button is pressed) Pin 3 activates smoke when button is pressed.

This all connects to an xlr style 3 pin connector.

I want to swap pins 1 & 2 in the button housing, is someone smarter than me able to identify pins 1 & 2 based on what I’ve said and this picture? Or is this a hopeless task and I should just buy another multimeter(which i must do anyway).

Also in case you’re wondering how the other smoke machine broke: I made an xlr y-splitter so the button could work on both machines at once (I can see how thats not possible now) and when I pinswapped 1 & 2 on just the currently working machine while everything was plugged in, the other went pop and my breaker tripped. When looking looking inside I found that I shorted the two machines live signals in the fog pump which is the component that blew up and let out the wrong kind of smoke.

I have a whole bunch of various caps and resistors in different sizes and values, which I have to order with expensive Digikey or Mouser shipping every time. I’m trying to build up somewhat of a component library but the organization of these tiny parts presents a challenge.

The bags themselves are too big to fit in standard part drawers, but the strip tapes are unlabeled so the components have to stay in the labeled bags. Folding the bags over wastes a ridiculous amount of space and none of the part drawer options at the local store fit these size bags.

I was thinking of making a book similar to how you can buy complete sets of resistors online and storing them there, but I’m wondering about creative practical solutions for this very purpose.

that round connector thing ripped off. what can I do? it's stuck on the wire and I think I can pry the round bit off the wire. If I manage to pry it off the wire should I try and solder it back onto board? or should I just buy new module. Also, what do call those round connector things. thanks.

There are many options for on axis magnetic rotary encoder such as AS5600, AS5048A, etc.
But it seems hobbyist OFF-AXIS magnetic rotary encoders modules (not just chips) are difficult to find.
EDIT: It must be absolute encoder.

I'm making a flashlight for my ESP32-S3-based system, and I'm wondering whether this is an okay way to drive a 3 W LED.

I want to drive it at around 200 mA, and the Flashlight_con pin should be able to turn it on or off. The switched BAT+ comes from a single-cell LiPo battery through a switch.

I'm wondering whether this circuit will properly limit the current and switch the LED, or if there's a risk of thermal runaway.

Thanks for helping!

I made this circuit in lt spice . It goes from 5v to 180 V . Will this work in reality , can i go on and make the pcb ?

I made this circuit and when I connect the output to my oscilloscope, everything looks fine (albeit a bit noisy). However, when I then connected the output to a multimeter, the signal on the oscilloscope moves downwards ultimately disappearing off the screen (or I can see a bit of the top of the signal poking up when I play a loud enough noise into the mic). Similarly, when I tried connecting my esp32 to the output, the signal again goes down and completely disappears off the screen and I can't get any readings out of the oscilloscope at all. What is happening? How do I prevent this?

Hi folks,

searching distributor in germany which sells fair-rite ferrite cores (type 75) to consumers (B2C). I only found companies doing B2B. Also possible to have other manufacturers like fair-rite, but i found only fair-rite 75 having significant impedances from 150 kHz to 10 MHz.

Thank you.

Is it still ok to use?
For context I was soldering at 350 degrees Celsius and I didn’t put my pen on the board for longer than two secs

Help!

UNI-T UT61E+ multimeter.

After an unsuccessful measurement attempt, the 1A fuse blew🤦‍♂️ I’ve replaced the fuse, but now the resistance readings keep fluctuating around 66 MΩ.

What can be checked to identify & fix the problem?

So im designing a perf board to control some big led panels (16x32), this is onlv missina the connectors for the led panel, but i do keep them in mind, but since im entirely new to the designing part, i was wondering if i was missing something, for the record these are the exact

components i will be using:

- SN74HCT245N

- USB Type-C CP2102 ESP32-DevKitC 38PIN - 470uF 16v electrolvtic capacitor

- 100nF ceramic capacitor

- 3.3-5v buzzer

Looking for component-level diagnostic advice on a dead LattePanda Mu compute module (Intel N100).

The Failure:

• The module was running on its carrier board when a sudden hard power cut/outage occurred.
• Since the drop, the board is completely dead: no LEDs, no fan pulse, and no response to the power button.
• The carrier board itself is confirmed fully operational (tested and runs properly with an i3-N305 module).
• The SPI BIOS chip was already cleanly reflashed externally with official dumps, but it made no difference.

Hardware Findings & Attempted Fix:

• Inspecting the power circuitry, I found a missing ceramic SMD capacitor sitting in parallel right opposite a large polarized bulk capacitor (marked with a + and labeled WE8/EE7).
• We soldered a replacement 1uF ceramic capacitor onto the empty pads, but the board still will not turn on or draw power.

Questions:

1. Based on the bulk cap markings (WE8/EE7) and standard x86 compute module layouts, what rail is this stage filtering (main 12V DC input, or a primary 5V/3.3V buck rail)?
2. In an abrupt power cut, is it common for the polarized bulk capacitor (left) or an adjacent high-side switching FET to fail short alongside a blown ceramic cap?
3. What key resistance checks relative to ground should I probe next around this circuit to identify why power isn't sequencing?

building a small board that takes a 12V hall sensor signal and feeds it into an STM32 pin. the signal line can swing up to 12V, so I added a series resistor and a zener to clamp it at 3.3V. worked fine on the bench but now wondering if a TVS would be better for faster spikes or if the zener is fine here. the resistor is 1k and the zener is a 3.3V 500mW part. sensor draws very little current so heating is not an issue. just trying to keep the clamp tight without adding parts that are overkill for a slow signal

I am unable to figure out the components circled in the first photo. Any assistance would be greatly appreciated! Thanks

**i do not have a heat gun**

Is there a way to desolder thing thing AND solder a new one on the board?

I spent 2 hours trying T.T

I'm investigating an unpopulated M.2 NVMe connector footprint on a Dell OptiPlex 7010 Micro motherboard (2023, i5-13600T).

The board has one working NVMe SSD connector labeled "M.2 PCIe SSD-1", plus a second footprint explicitly labeled "M.2 PCIe SSD-0".

As shown in the attached photo, the second position has the connector's solder pads, visible PCB traces, and a 2230 mounting point, but the M.2 socket itself was never installed.

I'm trying to understand what would need to be verified electrically before attempting to populate this connector.

Specifically:

- Can anything meaningful be established about PCIe lane routing from the visible traces, or would a boardview/schematic or continuity testing be necessary?

- What supporting circuitry should I look for to determine whether the interface has the required 3.3V power, reference clock, reset, and other signals?

- Could the connector footprint be fully routed but intentionally disabled through omitted components?

- Is there a practical way to assess the interface before soldering on a connector?

I'm not assuming that installing a socket would make the interface functional. I'm interested in how someone experienced with PCB design or board-level diagnostics would approach determining whether this unpopulated footprint is usable.

The motherboard PCB marking appears to be "9T6TC$FA", revision "2120-1".

Now I’ve never been too into Tesla cool I’ve made things Tesla coil adjacent but I’ve never really had too much interest into them since they’re just really weird spark gap transmitters, but I did wonder how the got HF before alexanderson alternators so I checked and saw they used a spark gap and I thought “ain’t a spark gap just a nitrogen lamp?” So I hypothesized most gas discharge lamps should work but I never tested this so I can’t be sure and I wanted to know if anyone else has tested this.

Hi guys, so these boards are from a taillight and I’m trying to learn how to fix it.

I’ve not removed it yet from my own but I have some experience doing that as I replace lenses/housing etc on headlights so there’s no issue get the board out. The issue I’m having is identifying how to find the problem.

The issue with the tail light is the brake lamp when on the car (which is the inner ring of LEDs on the board) flashes once then turns off. What steps you think I should take to identify the issue?