EDIT: WHY WOULD AN INTEGRATED 50 Ω RESISTOR BE BETTER THAN AN EXTERNAL 50 Ω RESISTOR?

Why does the 2SD1426 (a 600 V, 3.5 A, NPN switching device) have an integrated 50 Ω resistor?

I would have thought that it would be cheaper (less silicon used) to use an external 50 Ω resistor.

Or, internally, is this transistor composed of an array of multiple (e.g. 10) small devices in parallel, each with a 500 Ω resistor?

If anyone can shed some light, please let me know, I'm intrigued!

https://www.alldatasheet.com/datasheet-pdf/view/2568/MOSPEC/2SD1426.html

I ordered some DDR4 green pcb DIMMs from Ebay and they came wrapped in aluminum foil. This seems weird. Is it?

Hi! The multimeter UNI-T UT61E+ was purchased less than a year ago. Could you please tell me if this is normal? What is it? A manufacturing defect or an engineering design choice?

I live in an especially humid country and I recently bought an electronics component organizer (The 30 compartment Stanley organizer to be precise).

I previously used to keep my electronic components in a tightly sealed plastic box but the pins of most components eventually rusted due to high humidity.

This new component organizer is not sealed like my previous storage solution and I'm also planning to put 1 silica gel sachet in each compartment to help with the humidity.

Also, is it alright to not keep the mosfets, esp modules and other chips directly in the organizer without anti-static coverings?

Or should I use anti-static bags?

So... heres the deal...

Since I've found this subredit, i DO NOT TRUST maintenance people any longer.

This, is a board from an inverter slipt system.

The maintenance dude said:

- "the IPM Modu iS bUrNnEd HurHDUrRrR"

(sorry.. I'm really stressed out here, this board/module/thing is half the price of a new air-conditioning slip system here!)

So, i asked them to give me the board back, just because ill try to find an new one, online.

I lied!

I just teste this shit, using google to tell me whats what... the IPM module looks fine, and with google and a lot of youtube videos, its working properly!!!

But... i thought... I find help from the real experts FROM THE INTERNET!

I JUST TOOK the first picure of this board, and gave it the first look WITHOUT worrying about the said module, and i found a blown up capacitor -.-

So, the question here is...

Cam ONE tiny capacitor make this not to work? Also, can you guys help me identifying the issue, if there is one (besides this one blown up 100uf 25v capacitor)

Edit[1]: the bot told me to avoid "diagnosis by photo", but i dont want this.

There are two thing i want to know/understand 1 - can this capacitor render this whole board useless? 2 - what are the thing I should look for (Simce the maintenance dude lied, saying it was a faulty IPM module)?

I recently worked on a project that had a short sending some unwanted voltage through an arduino into my laptops usb port knocking it out for an about an hour. Thankfully it booted back up and is functional however I want to take extra precaution for next time beyond making sure my grounds are in order. I have read up a bit on usb isolators, optocouplers, and transformer isolated inputs and the logic behind them makes sense. If anyone has any product recommendations or general advice I would very much appreciate it

I just bought a batch of IRLZ44N N-channel MOSFET from robu.in and when testing if they were ok I discovered there was a dull metallic later on each and every one and I could scratch that off to reveal a shiny metallic later . Does this like stop the MOSFET from working as all test dead 🤔

Hello,

I found schematics to build a dual LFO that can output a triangle or a square wave depending on voltage (I've attached my references for better explanation). This is my fourth build ever so maybe I'm making an obvious mistake but I can't figure it out.

I'm following these schematics (fig. 1) with the components i have at home so some resistor values I'm using are bigger

Here are photos of my breadboard (fig. 2-3) (hope it's legible). I don't have a speaker plugged bc I tried every combination that made sense to me (+ to output C or D and - to ground, maybe I'm wrong ?) and it still doesn't work so I think the issue comes from the circuit itself.

Things I think could be wrong:

-i don't have a 300R so I used a 1K resistor, is that way too big ?

-Am I powering the chip itself wrong ?

-I'm still learning how to read schematics, particularly nodes where several components meet. Am I connecting the second leg of the pot to the resistor wrong ?

-Is the circuit correct but one of the pieces is broken ?

Here are the videos and websites I'm using as references, i know they all add a bunch of stuff to the circuit later on but the base circuit should work and mine doesn't.

https://www.youtube.com/watch?v=SqfumHiHc1A&t=138s

https://www.youtube.com/watch?v=Oh2Ix0G7Luk&list=LL&index=2&t=85s

https://kassu2000.blogspot.com/2015/10/variable-waveshape-lfo.html

Thanks for your help! This is really puzzling me!

Hi all,

I'm an EE undergrad (hardware track). My diploma thesis is a 2-in/2-out USB studio audio interface on my own PCB. It's my first PCB, so before I spend real money on boards and parts I'd love some experienced eyes on the plan. Block diagram attached.

The idea
- 2 mic inputs (XLR), shared 48 V phantom (one switch), gain 0–60 dB in 10 dB steps (rotary switch + fixed RG resistors, cap in series with RG).
- Noise-reduction technique I'm evaluating: each input drives BOTH channels of a stereo ADC (dual-mono) and the MCU averages them. The host still sees 2 mono channels, with ~3 dB lower ADC noise. I'll measure the gain from averaging at every gain step, comparing same-chip vs two-chip channel pairs.

Current part choices
- Preamp: SSM2019 (the THAT1512 went EOL in Sept 2026).
- ADC driver: passive divider (6.2k/1k, ~17 dB) + RC into a PCM1808, so the ADC reaches full scale ~1.8 dB before the preamp clips (≈ +20 dBu max input at minimum gain).
- ADC: 2 × PCM1808. DAC: PCM5102A.
- Line outs: DRV134 on TRS jacks. Headphones: op-amp + BUF634A. Output mute relays with a brown-out detector.
- Digital: STM32F407G-DISC1 board stacked on headers above the analog board. TinyUSB, UAC2 asynchronous with explicit feedback endpoint, 48 kHz / 24-bit in 3-byte subslots (the 1.25 KB USB FIFO rules out 4-byte subslots and 96 kHz).
- Clock: 24.576 MHz oscillator → ADC/DAC system clock and the MCU's external I2S clock input.
- Between boards: SN74LVC244A buffer (Ioff, to avoid back-powering) + a power-good line; 5 V to the dev board through a Schottky.
- Power (version A): bench triple supply (±15 V, +5 V), local LDOs for the ADC's 5.0 V and the 3.3 V. Phantom from a boost converter + capacitance multiplier (soft start, ripple filtering, output disconnect).
- Phantom protection following Bortoni & Kirkwood, "The 48 Volt Phantom Menace Returns". The single-channel test board will start from ojg's open-source thatmicpre KiCad project.
- Metal enclosure, XLR pin 1 to chassis at the entry point.

Noise budget (unweighted, 20 Hz–20 kHz, 150 Ω source)
- Predicted EIN at 60 dB gain: −128.7 dBu (target ≤ −125 dBu; worst case with min-spec ADC ≈ −127.5 dBu).
- Because of the divider, the ADC dominates up to ~50 dB gain. That's where averaging should help (~3 dB); at 60 dB the source dominates (~0.3 dB).

Plan
1. Demo on the dev board with cheap PCM1808/PCM5102A modules (incl. a first averaging measurement).
2. Small 2-layer single-channel preamp board.
3. 4-layer analog board for the full 2×2 interface.

Questions
1. Any obvious mistakes or bad part choices?
2. Is a passive divider + RC into the PCM1808 reasonable, or would you drive it differently?
3. Phantom: boost + capacitance multiplier, or something simpler? Anything missing in the protection network?
4. Is stacking the dev board right above the analog board realistic for low noise at 60 dB gain? Any layout/grounding advice?
5. Measuring without an audio analyzer: the card's own ADC + a 0.1 % attenuator + a true-RMS meter + REW for noise/EIN, and loopback as an upper bound for THD+N. Sensible?
6. Anything you'd simplify for a first PCB?

Thanks!

Hi I just got this cheap Old alarm clock radio I'd like to get working I have power to the clock and after opening the only thing wrong I can find seems to be this is something missing or am I missing something thank you

I am going to be attempting a repair on an iPad 6th generation with a broken charging port and home button replacement. I have opened several laptops and done basic stuff to them so I get the gist of electronic repair but I have never attempted to open up something like an iPad before. Really all I think all that will give me trouble is removing and replacing the screen.

What advice could you give for a first time iPad repair? Ive looked around the house for any old electronics I could practice removing the screen on but I didnt find any. I do know that ill need a heat gun and some kind of soft pry tool. This isnt a super high stakes repair since the worst case is -$20 but it would be nice to have it go successfully. Thanks!​

This is a control board in Candy/ Hoover dishwashers. I have the encircled device burnt out. It must be triac though the print on the board assigns Q27 to it! Can someone please help give the part number?

Canned air is getting expensive enough that I started looking at rechargeable dusters, but the ESD part is where I keep getting stuck. Some people say a short blast is fine as long as you hold the fan and don't scrape the board, while others make it sound like any dry plastic nozzle near exposed components is asking for trouble. For folks who work on electronics regularly, is the real concern the blower itself, the nozzle material, or just bad technique around unpowered boards?

So we needed to replace an obsolete legacy EDT EW12A03FLY.

Aliexpress said they sold them we tried one and apparently it worked on site but not on the test rig (would immediately cause letters to fade out on power up)

What if anything can I do to keep the LCD display on?

If you remove power and put it back and the letters come back immediately and then fade out again.

I opened up an old laptop hoping I could fix it. On the plastic I saw this corrosion like spots. Any idea what it could be?

the beamz s700 smoke machine has a remote control with 2 leds and a push button. but the smoke machine has no dmx, so i cannot remotely make it produce smoke. i was thinking maybe it's possible to hack the remote control. i opened it up and measured that there is 220V AC between the brown and black wire. i thought maybe the best course of action is to have a custom pcb onto which i can solder the 3 wires and i can have remote control. so the pcb should have 2 leds and a processor and a component that electronically performs the job of the push button, so that via wifi i can remotely connect the 2 fields which previously were connected to the push button.

any advice on how to proceed? i don't know anything about making pcbs and there being AC involved feels kind of dangerous so this should be done with care and expertise.

It works but when you switch it off it either 1) stays on, 2) turns off, or 3) turns off and back on a few minutes later. Is this something that's somewhat easily fixable? Buying a new one will cost $100+

I have this led panel as a backlight in a picture frame, but the usb-connector that powers it, was knocked off (see pic below). How can I resolder it back?

I am an electronics student and I have been struggling with this assignment for a few days. I need to design a stiff VDB PNP transistor circuit. The only variables I have so far are Vcc=5 V, Ic=20 mA, and hfe of 200 is assumed. I am using numbers for a red LED so far, so 1.8 V across it. I am getting stuck at figuring out how to calculate R1and R2. I don't necessarily want the answers straight up, but some guidance on where to start would be very helpful.

I'm trying to read the EEPROM on this board.
Chip: Atmel 24C08N (I2C), right next to the NEC MCU.
Setup:
Black CH341A, SOIC8 clip with the green adapter
NeoProgrammer / AsProgrammer, _24C08 selected, I2C mode
Result: always "IC not responding".
I think the clip is powering the whole board and the voltage drops. I'd rather not desolder the chip or lift pin 8.
Is there any way to read it in-circuit, like powering the board separately or any help guys?

Title. I've been working on some pet projects for a while now and I'm looking for diagram tools that I can use to map out my systems. I struggle to explain how my projects work when I'm showing them to people or asking for help, and I also want the documentation for my own use as I work with the components I'm "designing" (i use that term loosely as I'm pretty much re-inventing the wheel for my own educational benefit)

For some reference, I'm using a simulator to build a reduced-instruction 16-bit computer, mostly because I'm interested but also because I've been exploring computers for a long time and I wouldn't hate getting into the field professionally. Also, I know I need schooling to get into Comp Eng, but I'm just trying to get myself a baseline as the economy is kinda buns.

My low-side N-MOSFET turns on unintentionally when a 32V supply is applied to the drain. The gate has a series gate resistor, an external Miller capacitor (gate to drain), a Cgs capacitor and a gate-source pull-down resistor. I see a spike on the gate of the MOSFET, which turns on the transistor just enough to see a current spike through the drain.
I suspect dv/dt-induced turn-on through the Miller capacitance.
What should I check or change?

I try to use this circuit to control a beacon. I know this isn't perfect by any means, I have no voltage regulator and I could further limit the current that flows through some components. However, my problem is the following:
The astable multivibrator on the left should activate / deactivate the BC557 to create short "beeps" via PLSE. However, the voltage on PLSE is never dropping below 7 V (measured with a multimeter), which means I won't get a single tone out of my beacon. I guess this is related to the size of the resistors, but I'm not sure what to do to fix the circuit. Any help would be much appreciated!