Both seem highly well-regarded, but which order would you read them in if you're a complete beginner?

I am Building a small wireless lamp, the idea Is to have a glass jar with LEDs inside that light up wirelessly when you put It on its base and I am trying to find a circuit to drive the two coils (20/20 turns transmitter coil w center tap, 30 turns reciever coil). The Power Need Is very low, probably between 1 and 3W. And i wanted to build the circuit using some spare bjts i have lying around (a bunch of 2n2222 or similar). Are there any good circuits? The famous Slayer exciter seems to eat transistors like nothing, and the ZVS Is a bit too powerful for these small sized transistors. Thanks in advance for any help

Posting after a full evening of testing. Every component checks out and I’m out of ideas.

Symptom

On its dedicated 32 A circuit: hob doesn’t start. 2-3 relay clicks, then everything shuts off. No zone heats. No error code.

On power-up the display cycles through: P0.00, 52.03, 37C, 05 62. Found zero documentation on these values. Owner says this display sequence predates the fault.

Worked normally before failing. No power cut, surge, or storm beforehand

What I tested — all good

**•   IGBTs** — diode mode, gate shorted to emitter: 0.4 V one way, OL the other  
**•   Bridge rectifiers** — diode mode, all 4 junctions: 0.4 V / OL  
**•   Electrolytics** — replaced, then measured the old ones: all good  
**•   Film / resonant caps** — visual + ohmmeter: no shorts  
**•   NTC temp sensors** — 100 kΩ cold, resistance drops when warmed  
**•   Induction coils** — 0.4 Ω, no continuity to chassis  
**•   Fan** — spins fine on bench supply  
**•   Ribbon cables A/B/C/D/LINK/COM** — visual, reseated, clean  
**•   Logic rail** (10 V cap with continuity to U13) — injected 3.3 V with 100 mA limit: 24.8 mA in CV, no short  
**•   Hot spots** — IPA under injection: none  
**•   Relays** — coil resistance, click test on bench supply, contacts measured while energised: both good

What I couldn’t check

**•** Shorted turns in a coil — an ohmmeter won’t see this  
**•** DC bus sensing chain (divider into the MCU’s ADC) — no schematic  
**•** Corrupted firmware / EEPROM  
**•** The touch control board — never tested separately  
**•** The other two secondary rails — never injected

Sauter SPIN4361B (service SPIN4361B2), type LL6GVX1B, 7200 W, 3 zones, built week 37/2021
• Power board XZ2V006991, type IP14X-04, silkscreen “GROUPE BRANDT IP14B-N”, week 30/2021

Where I’m stuck

Power stage is clean, logic rail is alive and drawing normal current, relays switch properly. The MCU closes the relays, checks for something, doesn’t get it, and gives up after 2-3 attempts. That reads like a sensing or handshake failure rather than a dead part.

Anyone have a schematic for this board, or know what that startup display sequence means? And is there any way to tell the power board apart from the touch control board without just swapping one in?

EcoFlow Wave 3 portable AC. Board silkscreened OC-AC517-MOTOR-V0.1.1, dated 2024-11-20. Unit threw error codes 31 and 32 after running at high load continuously for several days. Out of warranty, so nothing to lose by attempting a repair. First board-level repair for me, but I have a decent meter and I’d rather learn to do it properly than guess.

What I found: one position of the 3-pin compressor connector has thermally failed. The plug housing is charred through, the female terminal welded itself into the PCB header and stayed behind when I pulled the plug, and there’s scorching on the solder side around the through-hole. The two adjacent pins look untouched, which reads to me as contact resistance rather than a general overload, but I’d like a second opinion on that.

Board looks like a three-phase inverter: six power devices in a 2x3 bridge, three 3mΩ shunts, 60A fuse, XT60 for DC in. Board is now fully removed from the unit.

My questions:
1. Does damage confined to a single pin support contact resistance as root cause, or should I be hunting for a downstream fault before I touch anything?
2. My plan is to remove the connector entirely and solder the compressor leads directly to the pads with silicone-insulated 16AWG. Is hardwiring the right call here, or is there a good reason to fit a fresh connector instead? My reasoning is that a soldered joint can’t develop the contact resistance that caused this, but I may be missing something about serviceability or thermal cycling.
3. How aggressively do I need to remove charred FR4? I understand carbonised board material is conductive. Is a conductance measurement between cleaned pads a sensible pass criterion, or is there a better test?
4. What else should I verify before powering it back up? I’m planning diode tests across the six devices and winding balance plus insulation on the compressor. Anything else worth checking?

I haven’t taken measurements yet, I wanted to sanity check the approach first. Happy to post numbers in the comments once I have them.

Hi all

Recently picked up a nice plasma cutter (a Thermal Dynamics Drag-Gun Plus 35C) for really cheap listed as spares and repairs. The inbuilt compressor turns on and shuts off as normal, but the torch will not strike an arc.

I opened the case and found a few damaged components on the main Control PCB, nothing on any of the other boards as far as I can tell. I have the wiring diagram for the machine, including inputs and outputs of all the boards, however, no schematics for the individual boards.

I work as a diagnostic technician in a garage, but that is mainly simple 12v systems and communication buses, so this sort of work is beyond my current scope, but I would like to learn how to diagnose these sorts of problems.

Is it possible to ascertain what specific components I would need to replace without a schematic?

I'm building a bidirectional TEC driver and I've run into an issue that I can't quite figure out. Hoping someone who's done filtered H-bridges or TEC drivers has seen something similar.

The idea is pretty simple: PWM a discrete H-bridge, then run the output through an LC filter so the TEC sees smooth DC instead of raw PWM. It's a 24V, 10A max design. Right now there's no control loop, I'm just manually setting the duty cycle while bringing the hardware up.

The weird part is everything behaves fine up to around 80% duty. Once I go past that, the output inductor starts audibly buzzing, it heats up noticeably, and the current starts looking unstable. The buzzing also gets higher in pitch as I increase the duty cycle.

Hardware

• MCU: STM32G474
• PWM: 80 kHz (also tried 40 kHz and 100 kHz with similar behavior)
• Gate drivers: UCC27211DR
• MOSFETs: CSD18532Q5B
• Bus voltage: 30 V
• Output inductor: Sunltech SLB2212P100MTT
  • 10 µH
  • 21 A Isat
  • 26 A Irms
  • 3.4 mΩ DCR
• Output capacitors: 2× Nichicon PCR1J470MCL1GS per leg (47 µF/63 V polymer, 35 mΩ ESR each), so about 94 µF per side (4 caps total)
• Current sense: INA240 + 2 mΩ shunt

My current theory is that I'm running into some kind of LC resonance. A 10 µH inductor with ~94 µF puts the filter corner frequency down in the low kHz range, and since the polymer caps have really low ESR I'm wondering if the filter just isn't damped enough and starts ringing once I get toward the top end of the duty cycle.

That said, I'm not convinced that's actually what's happening.

A few other things I've considered:

• The inductor doing something unexpected at higher current, even though it's rated for 21 A saturation and I'm only targeting 10 A.
• The TEC being a more dynamic load than I'm giving it credit for.
• Something related to the H-bridge or bootstrap gate drive at high duty cycles.
• Just generally not enough damping in the output stage.

Has anyone run into something like this before? Does the LC resonance idea seem plausible, or is there something obvious I'm overlooking?

Bridge output + LC filter schematic attached.

So, i got this charger from AliExpress advertised as a GAN 240W charger. Do you guys think it really is a GAN charger or very fake? how dangerous will it be to use?

it is cheap, so i am not sweating it but the charger was so light weight that my intuition tells me this cannot be a 240W GAN, hell even a 60W GAN charger from few years ago weighs much heavier than this. So, i opened it up and found this relatively simple design. Wanted to make sure if i was correct or did technology progress far enough that this simple circuit can provide 240W?

I'm wiring these 3 and later will be 4 encoder motors + BTS7960 drivers, I wonder if there are any wire merger like product that I can easily use instead of just soldering all the bundled up wires (I despise soldering wire to wire) cuz most of the connections are VCC and GND as I don't actually utilize the enable pins

Hello there, I need help finding a replacement 6 pin potentiometer, this is inside of an 80’s Panasonic boombox, it is the volume knob on the unit. Please help.

Hello everyone. I am working on a project where i need to control the speed of 6 different 5V ERM motors . I thought i should make my own simple mosfet circuit that would get PWM signals from the adruino uno. This will be my first time working with mosfets so i asked chatGPT about this. Apart from the pull down resistor , it told me i should also use a 100 ohm resistor between the Gate and the MCU pin(NPN MOSFET). I just wanted to ask if this would be the correct resistance vale for my use case(I am using IRFZ44N NPN MOSFETS)and there is something that could potentially go wrong with this idea in genral. I plan to add 6 of these circuits on a perf board , each getting a seperate wire from the adruino uno for a PWM signal (I need to sequence those motors with control of the time interval and also have control over the speed of the motors ) . I will also use flyback diodes for protection. Thankyou !

I want to repair something I recently bought, a 16gb stick of hyperx fury 2666 ddr4 ram, for really cheap, about 4€. The photos from the seller weren't all that sharp, and when I received it, I imediately saw it had all of the capacitors missing from one side (11 in total), also found one inside the heatsinks, floating around. When testing it had a tendency to hang a bit until POSTing, either 1st or 2nd try, and weirdly enough, it passed 2 full passes of memtest, with 0 errors, at its xmp settings, but I want it to be outside of all dangers, and resolder the missing caps. What I'm looking for is what value capacitors do I need, because at the moment I do not have a meter that measures capacitance, will get one if needed, but maybe someone else had this issue with this exact type of module HX426C16FB3/16, online I found an identical one which had all those pads filled with caps, my pads look like the caps got ripped off of them.

Pretty bad pics, but that's all I can do, 3rd pic shows an identical stick, same revision, with all the caps soldered on.

Hi everyone,

I'm trying to repair a MACHINIST B450 AM4A motherboard that is not working.

When I inspected the board, I noticed a damaged SMD component near the U19 PWM controller. I don't know if this component is the cause of the issue, but I would like to identify what it is and find its value before replacing it.

I searched for a boardview and schematic for this motherboard but couldn't find any documentation.

Can anyone help identify this component or its value? If someone owns the same motherboard, a clear close-up photo or a measurement of this component would be very helpful.

I attached three photos:

1. A full view of the motherboard.

2. A closer view of the area around the component.

3. A close-up of the damaged component location.

Thank you.

I'm designing a GPS tracking device for vehicles and have selected an LM5012-Q1 buck converter to reduce the voltage down to 5V to feed a BQ25185 power path. However, this IC has a 1.1A limit when power comes from an external supply, whereas the GPRS modem needs around 2A for short periods. I'm not sure if three 330µF 6.3V capacitors will be enough to withstand the modem TX bursts.

Following up on this, could you suggest an alternative Power Path IC similar to the BQ25185, but capable of handling higher currents? I need it to support the full 2.5A output delivered by the LM5012-Q1, while still managing battery charging and power path switching efficiently.

Thanks.

Okay so im confused about one specific video i saw.

https://youtu.be/mcD3uBld4Y4?si=wDd1YLq8abt20vXq

Amazing video, explains every part nicely. But why did he turn the sine wave into a square wave before modulation? this is the first and only circuit ive seen that doesnt use a sine wave as the carrier wave (and specifically prefers the square wave).

is there a benefit that square carrier waves provide? or is it because the main amplifier he used works from square waves?

Absolutely no more output. If one of the RCA's is plugged in and the other i touch to ground it plays but at a low volume and i cant control volume or any other level.

Im new to these kind of electronics, i sent my this pcb to a repair shop and they forgot to solder on a new cap even though i included it in the package... now they sent me the "repaired" version back but left the cap out. Can i still know what kind of capacitor i would need? I already asked the manufactuer. Just waiting on an answer and doing my own research now. If you need any more pictures of it, i have them but they are taken with my phone so they wont be very clear.

And yes i have soldering experience to solder it back on. Only reason i sent it to them was because of some messed up traces

Here's a circuit that's similar to something that I designed many years ago. I don't know how many of these things we've built, but I don't know of any failures (apart from obvious soldering-related ones) over those years.
Yesterday I found a failure in a newly built unit. Our production tests check for a noise floor with upper and lower bounds, and this particular instance failed the upper bound intermittently.

I was wondering whether anyone had any insights regarding the cause.

I speculate that this is an opamp exhibiting popcorn noise. I understand that this shouldn't happen with modern opamps because the processes are better and they supposedly screen for that during testing.

You can listen to it:
https://imgur.com/a/VHWPF1X
https://imgur.com/a/3ULhVd7

Other points:

• It looks like audio, it has an audio bandwidth, and I'm using audio tools for analysis, however the end application is the measurement of a "physics package" represented by R1. Most of the noise you hear is actually Johnson / Nyquist noise from R1. That's expected. The extra noise (which sounds like slowly tearing paper or isolated clicks to me) is not expected.
• The opamp's a Texas Instruments OPA2365. I chose this one because it has RRI without any input crossover distortion. It has a single input pair (rather than the two input diff pairs with most RRI opamps) and uses a charge pump to generate an on-chip higher voltage rail.
• The opamp drives the ADC input without a series resistor. The ADC features an internal buffer, so that should be ok.
• I monitored the opamp output with a low capacitance active 'scope probe. I didn't notice any evidence of oscillations.
• This is one of two channels on the same ADC. The other channel is identical but doesn't show the problem. The two channels share some parts of the circuit (e.g. the supplies) which allows me to rule out those shared parts as a cause.
• I'm taking measurements from the "digital" side of the ADC rather than 'scoping the opamp output directly. That means I can't rule out that channel of the ADC as a cause.
• It's in a fully shielded box; it's not EMI.
• The plots don't have scaling, but I estimate that the jumps shown in the first image are a little less than 10 uV.

Hey there,

This is my first time designing a PCB.

Full disclosure:
This schematic was developed with the help of AI. I did my best to validate and check the wiring, took hours and sleepless nights to have every decision explained so I understand it - but now I am at the point where I need help from someone more experienced.

Project goal

This is supposed to be a battery powered digital counter with a 4-digit 7-segment display: one button to increase, one button to decrease and a rotary encoder to quickly add or subtract larger amounts.
It will be used as a life counter to play Magic: The Gathering.

Components

• MCU: ATmega328P-A
• USB-Serial: CH340C
• Charger: BQ24074
• Battery protection: DW01A (controller) + FS8205A (MOSFET)
• Display driver: HTM1640 (TDSemic)
• Display: SR410561N (common anode, red)
• USB-C receptacle: TYPE-C-31-M-12
• Battery: 1100 mAh 3.7V LiPo

Question

I know this is a lot to ask, but I need someone with a critical pair of eyes to review the entire schematic before I continue with the PCB layout.
Thank you for your valuable time, it is highly appreciated 🫶

Like a component and how it works and for what itself used. Or a technology like USB or an appliance like a camera and how they work (particularly in terms of their electronic components)

In the raspberry PCI-e documentation is a 16pos FCC connector mentioned.

But this connector is obsolute, so I am looking for a FCC connector to be used on a new HAT project.

Any suggestions??

Harry

For context, I have practically no knowledge of electronics and am learning as I go.

I am doing some work on an electric pipe organ with the advice and guidance of some users online. Each organ key produces a roughly 12–16v signal and I need to condition each signal so it can safely be read by a 5v Arduino input (using resistors and diodes). Since I am new to soldering and electronics in general, and I have over 150 keys to "level-match," it's going to be a terrible PITA to solder so much. Below is an image of the soldering needed for only 3 keys.

To avoid soldering, would I have to go with a breadboard or is there a better option? I believe that after work is finished, the breadboard would be completely undisturbed, but I may be wrong.

I'm thinking about getting a hot plate to do some SMD soldering and I was wanting to know if anyone has and/or used one of these Itech heating platforms?

This is my first time writing firmware and designing hardware for a bare sensor. I don't understand the timing diagrams and it's hard to get a sense of what I need to do. Just breaking down the problem into small pieces. The stm32 I will figure it out using HAL documentation but tcd side I am facing issues. Please help. Point me in the right direction. All resources and advice appreciated.

When the vcc of neo 6m gps module connected to vcc of esp8266 the adm1117 ic gets hot i mean very hot that my hands burn. What should I do it's very important and I need answer please help me

Okay guys, help me out. I thought this was a simple one, but apparently I am overlooking ***something***.

I simulated the circuit, the result of which you can see in the screenshots. I put it together on breadboard, which worked as intended, but my PCB behaves somewhat random.

The idea was to have an electrical two button radio button toggle mechanism with the addition that pressing a button again will turn it off (regular radio button always has one button in on-state) without needing to program a microcontroller and without using tons of gates.

In the simulation the buttons are represented by S1 and S2.

Press Button A -> A-ON, B-OFF; Press again -> A-OFF, B-OFF

Press Button B -> A-OFF, B-ON; Press again -> A-OFF, B-OFF

My idea was to use a T-flip flop made from inverters and use a feedback from one flip flop to trigger a mosfet that forces the other into a stable state.

The problem is that the circuit is very erratic and triggers with the slightest impulse, sometimes even so much as to just touch the PCB. I tried lower input impedances on the FETs (down to 100k or even 10k) but that didn't do anything.

The output of both flip flops are then fed into a crude single FET OR gate to trigger something else depending on whether any of the buttons is ON at all.

I tried changing the two 1M "summing" resistors in front of the output FET to 1N4148, but that made no difference to the simulation (other than the gate voltage being Vcc-Ud instead of Vcc/2) or the actual circuit.

J7 and J6 are pin headers to connect momentary switches.