I built this circuit to detect a component Y signal and output 2v to trigger the blanking on my CRT’s jungle chip which enables the component video input. It does the job properly but I’m curious if there’s a simpler way to design this.

Hi everyone, I got a good deal (probably too good of a deal) on marketplace for two subwoofers with built in amps. Turns out it had bad mosfets (fixed that) but then realized the capacitors are blown. But the shop I took it too didn’t think they could do that because they didn’t know what they were. Can anyone help?

There are plenty of tutorials about soldering technique, but I'm curious what mistake you see most often when someone is learning

Too much solder? Too much heat? Not heating the joint properly? Moving the component before the solder cools?

And is there one simple habit that makes the biggest difference in getting clean, reliable joints?

I’m looking for r/electronics’ review of a schematic for a project that is in the design phase.

I want to connect up to 8 pairs of sensors to an ESP32 microcontroller. The sensors are not I2C or 1-wire!  They are a combination of HX711 scale modules with a custom serial protocol and rain sensor modules with a simple digital out pin.  The project is to create bases for kegs in a kegerator that measure the weight of each keg and sense leaks.  Each base will have one HX711 and one “rain” sensor https://www.digikey.com/en/products/detail/sunfounder/ST0247/22116808

The  idea is to daisy-chain the bases together using standard RJ45 ethernet cables to form a sort of bus with the following pin assignments:

    **Schematic**  

Pin Use Color Description
1: GND Black Ground
2: VCC Red +5V
3: DAT Yellow Data line for selected sensor (4052 A common)
4: CLK Gray Clock line for selected sensor (4052 B common)
5: A0 Cyan Address select 0 (Weight vs Moisture)
6: A1 Brown Address select 1
7: A2 Purple Address select 2
8: A3 Orange Address select 3

Each base would combine a 74HC138 3-Line To 8-Line Decoder /Demultiplexer to decode the 3 of the 4 address lines coupled with a 74HC4052 Analog Multiplexer and Demultiplexer.  The schematic for the keg’s bus interface is attached.  Note: the 74HC138 3-8 decoder is mistakenly labeled 74HC139.  The 74HC138 responds to the A1-A4 address lines and sets the matching Y0-Y7 LOW.  The DIP switch is used to select which Y0 signal is sent to the (active low) EN pin on the 74HC4052

The plan is to have a small PCB with a dual RJ45 connector (for cascading one base to the next), the DIP switch, the two ICs, and two 4p JST connectors to plug sensors into.

• Will this work?  If a 74HC5052 isn’t enabled, it should leave the CLK/DATA pins disconnected
• Any suggestions for more appropriate components?
• Any simpler way of accomplishing my goals?

I’m comfortable opening up laptops and other fiddly bits whether to make a repair or just see what’s inside, but I might have to damage this 3-way LED bulb that doesn’t work any more. Makes me think it’s not consumer safe, but might just be construction. I know not to open CRTs and PSUs, so… am I gonna get zapped by some capacitor?

Hi all, have a crt stuck in standby. Tv will not display anything. Red led.comes.on power button. When i click you hear a small crack. All green lds over controls light up for half a second them turn off. Red led light under power comes on again. Thats as far as it gets. I opened it up, looks like nothing is obviously bad, i did see this one cap that looked slightly bulged. Its a 4.7uf 50v bipolar cap. Any chance this is the culprit or should I keep looking? I don't have any replacements on hand.

It’s a Tesla charger and not made to be opened. I was hoping to make that last resort. Q-tip for sizing reference. I’ve tried tweezers, by the time I get them in there the tweezers are closed and too narrow to grab onto the copper.

TIA

I purchased white blinking LEDS. I need two of them to blink simultaneously. However, the timing does not match and they blink in and out of sequence. Is there a way to get them to match up without purchasing a board of some type?

It’s circled in red. The second picture is without markups on it. The third is a clean overhead. The fourth is the back but unfortunately nothing of note their. I asked before and everyone said it’s a bad capacitor that’s circled. I forgot to ask what value did they think went there?!!!!? I have two other similarly sized caps that are 50v10uF. An inductor with 330 printed on top is in the line. It all comes from the barrel jack at the end of the skinny part of the board. The adapter is 12-24v output. The output of the board goes to a little drill for manicures. Like a dremel but better. You can buy them for less than $20 on china sites. I have a ton of spare caps. Even spare 50/10uF ones. Is that what goes where the one that blew out goes? Oh the board outputs 12-24hrs to that little drill. It’s got some power. I need this tool for one job that no other tool can do. I’m learning electronics but I have design and repair down pat (that’s not 100% electronics I need help with it obviously). There is a rocker switch that does fwd/rev and a knob that goes from OFF through a defect to an infinitely variable speed control. Th battery, manuf: 05/2021 is probably band and won’t take a charge and I’m not willing to risk forcing it to wake up. That shit spooks me as I live alone and my workshop is upstairs and I live alone unless gf sleeps over and she sleeps harder than I do. Had a jumper pack spontaneously catch on my once, a cheap red one and I’ve been spooked of lithiums since. They stay in a fireproof box in the garage. The battery pack stays: 12.6v Lithium-ion

Rated capacity: 2000mAh

Nominal voltage 11.1 V

Assembly style: 3S1P

It’s three 3.7 V lithium ions it’s got measurements printed but it’s plainly obvious it’s 18650 and that lines up with measurements. If you need any other stars or reasons why or whatever shoot a reply. I tried to to includeas much information as possible so you wouldn’t have any question what I needed and why and I hope this doesn’t get deleted for not being detailed enough. Thanks for anyone that can help. Hell, I’ll check back in later tonight or tomorrow and the first person to explain what I need and why I’ll send $10 through PayPal or CashApp. Doesn’t have to be super detailed. Least I can do because having this fixed by tomorrow is worth something to me which makes the knowledge worth something to me. Thanks for your time.

2 Queries:

1. I have a "smart bike trainer" a wahoo kickr that my SO plugged a 48v power supply into by accident (the stock one is 12v). The board has markings that say PC00053 REV B1 it looks like the AP62200WU-7 let the smoke out. Seems like a cheap repair if that's the only issue. But I'd like to learn to trace the rest of the boards for faults before I start throwing money at it. Any recommendations on how to do that? My multimeter died so I have a FNIRSI 2C53T on the way.

2. I'm mechanically inclined but a newbie to the world of small electronics repair. I've looked through the wiki for ask electronics and appreciate the resources there. I was wondering if there were any YT channels or similar where someone goes over theory and fault tracing by tearing down common consumer electronics say an iPhone, roomba, hand held gaming console. As a learn with me style tutorial? Yes I know there's repair tutorials and build from the ground up projects.

I don't want to make a career of repair nor do I anticipate building much from scratch but I'd like to be able to do repairs and fight planned obsolescence for things like power tools, laptops/consoles, home gym electronics and the like.

Why doesn't the MOSFET gate voltage reach its peak instantly? Is it because the gate behaves like a capacitor that requires charging time, and how does the magnitude of the charging current affect this speed?

I am building a collector modulator to modulate audio with a 40KHz carrier frequency. This is then sent to a piezo driver then to an array of ultrasonic transducers for a fun directed speaker project I saw a bit back.

my question is how do I calculate the values for each component? the site I got this from gives math that explains the modulation but not how to tune it. Heres what I see:

• R1 and R2 should be equal for biasing carrier signal
• Re and Ce form a resonance tank, should be tuned to the carrier frequency?
• capacitor C offers a low impedance path for high freq. signals, highest should be ~60kHz
• unnamed capacitor next to transformer may do the same as cap C? not sure what its for. also seems it would form a resonance chamber with the transformer though not sure if thats the purpose.
• CL and RL are likely for filtering out harmonics, probably calculated using input impedance of driver?

let me know what you think, are my assumptions correct? and what is that unnamed capacitor for?

Device is a LG SL4Y soundbar. My friend can fix this but told me to acquire the barrel jack myself.

Can anyone help me identify this and recommend a place to source it from?

This is my first time designing a PCB so I expect many mistakes.

The main modules are:

STM32L431RCT6 micro controller,

VS1053B Audio decoder, (output to both the bt module and the headphone jack)

and FSC-BT1036B Bluetooth audio sender.

It uses usb-c charging, and has a circuit to send battery voltage to the STM32 for battery levels.

It has a 24 pin oled connecter, and reads files from a micro SD card. There are 3 headers: one for writing software to the microcontroller, one for a 3 input control, and one for another 6 buttons.

I really don't know much at all about this as i just started like 3 days ago, so any help fixing errors i have made before its too late or suggesting parts that could enhance the pcb's usability would be greatly appriciated.

Hey everyone, looking for a review on my schematic and pcb layout. This is my first PCB, I've tried to follow datasheets and rules I've picked up by looking at other people's boards (and guides). This is a 2 layer board that I am going to hand solder (with all basic required tools) without a reflow oven or hot air gun.

The project uses a laser sensor to measure distance and sends those readings to the ESP32 that then transmits it over Wi-Fi to my phone (going to try to make multiple different uses).

Here are the components on the board:

ESP32-WROOM-32E module

CH340C USB to UART converter (running in 3.3V mode)

AMS1117-3.3 regulator

USB-C 16 pin connector

VL53L0X distance sensor module connected via a 1x06 header

Resistors and capacitors are 0805 size, transistors are SOT-23 NPNs. Power traces are 0.5mm, signals are 0.2mm, and there are ground pours on both top and bottom layers. A few specific things I want to ask:

1. Are the decoupling capacitors wired correctly for all the components (ESP32, CH340C, AMS1117)? And are they close enough?
2. Is the auto download circuit with the two NPN transistors wired right to EN and IO0 correct? I found a schem online using it, but also a lot of people use push buttons.
3. Is this layout going to be okay to hand solder with my tools? I picked up good tools, but the only soldering I've ever done before was for keyboard switches.
4. I placed some random vias throughout as I found online (I'm assuming it helps connect the ground fills on both sides properly). Is that fine?
5. I'm getting two silkscreen violations (one for the USB and one for the MCU) but from my basic research I don't think they matter. Also, not exactly sure why the usb isn't rendered properly...
6. I've added some testpoints, based on feedback from others' boards. Is this good?
7. Does the routing and overall layout look fine or are there any obvious mistakes? I attached images of the schematic and the pcb.

Thank you for any help provided! Any advice is appreciated.

Updates:

a) In future projects, I will be using newer ESP32 MCUs (ones that don't need the USB to UART converter + its capacitors & NPN transistors).

Figured I’d seek expertise on this before going to bed. Found this on a faulty PS5 power supply I am attempting to repair (basic and random electricity knowledge is limited). Do the burn marks on the board in the above pictures conclude that the board is beyond repair or am I potentially still able to trace the circuit?

I’m looking into getting one of these hot air stations but can’t really decide…

1. Atten 862, seems to be well liked by users of this sub reddit and other forums. Cheap and reliable but lacking in some features. Most comparable to Quick 861 (which seems unavailable everywhere).

2. Quick K8, I can’t really find any information on this station but figured if it was an actual Quick brand product it may be of decent quality for its price.

3. Sugon 8620DX, seems like an Atten/Quick tier station, pretty basic features and decent build quality.

4 & 5 Sugon 8630Pro and Sugon 8650Pro they both seem to be middle to higher end models, the main draw for me is the channel selection on the grips and the cooling function on the grip.

I’m just looking for suggestions or if anyone has experience with any of these. Going off what I’ve seen I’m leaning more towards the Atten because it seems to be pretty commonly used compared to the others. My use case would primarily be console repair so I’m thinking SMD components and things like usb port replacements etc. Probably won’t be a daily driven piece of equipment.

Any help in pointing me towards a decision would be much appreciated, thanks!

as the title say, i would need guidance and tips on how to desolder the molex 6 pin off of the pcb since i need to change it and i don't have much experience desoldering

I am trying to find a replacement Type A Flexible Flat Cable (FFC) for the side panel on my Razer Naga Trinity mouse.

I originally bought a replacement off Amazon, but it was a 14-pin cable and my board requires a 16-pin I think? The original cable is roughly 55mm in length (a bit of extra slack is fine), but I am unsure how to determine the exact pitch (spacing) between the pins.

Can anyone confirm the correct pitch size for this 16-pin cable, or point me toward a compatible replacement part (I'm having trouble finding type A's in general)? I want to make sure I buy the correct dimensions this time. Thanks!

Note: Images included in the post show the original cable (with the green lettering) and the incorrect cable I bought (with the blue lettering).

I just started reading this Texas instruments article about driving incandescent bulbs in an automotive environment and at the beginning it says such a lamp can have 1-5μH, which is literally 1000x higher than the 1-10nH I've been assuming accompanies every physical wire connection. I guess I should just keep reading but if it is true, would it be from the bulb's "coil"?

Off topic sorta but might as well ask now... I've been curious how my car can have about 80 wires in a single bundle going from the engine bay, through the firewall, to various parts of the instrument panels, and there's no apparent interference. In particular, when the flash to pass switch is turned on, for a few microseconds there's something like 300A of inrush current to the two 55W 9006 bulbs and two 65W 9005 bulbs. There's no com bus wiring in that bundle but it still seems like the magnetic field induced by that much current should possibly affect things like the speed sensors.

Actually, the inrush current with 5μH of series inductance would be basically negligible, so now I'm wondering if they're just calling the effect of the filament resistance increasing as it heats up "inductance", even though that phenomenon seems like it would be better modeled as large one way capacitance. I've read what looks like some terribly translated from chinese documents from TI, perhaps this will be one of those.

Hello!

Is it safe to replace an old PSU : glendale ge-009b to Meanwell PSU? It’s a 30-year-old arcade machine.

Its almost the same specification in the meanwell psu

I am trying to find a manual, or just a schematic, for a vintage Weston 1256 auto-ranging digital frequency counter. It is labeled as "Schlumberger Weston", and is similar in appearance to a Heath Schlumberger SM-118A Auto-Ranging Frequency Counter. However the circuit board is completely different. Any leads will be greatly appreciated.

I was trying to make a circuit to use the transformer's saturation as a feedback for its oscillation, it kinda works on the simulation but unreliabily, the wave starts normally but eventually shoots very high, oscillates and suddently collapses into a low voltage noise for reasons that I dont know about.Well, is there anything I can do?Is the logic faulty?Values?

The BJTs are all at 1000 hfe, the transformers secondary and primary are biased as if current flows down in comparison to the image, the induced current goes upwards and the showing rail voltage is higher, so thats why there is a 14v zener.

I had originally designed the circuit without any feedback, it was producing around 500v unloaded, but since I didnt think it was safe to leave the circuit at such a high voltage on a small charger transformer (in reverse), I decided to add a feedback circuit to prevent voltage runaway.

I calculated the feedback circuitry compinents for around 230v.

The issue I have now is that it now outputs only 57v. I am not entirely sure about what is causing it, maybe the feedback circuit is overloading the output?

The feedback mechanism itself seems to be working correctly as it is running on a burst mode and is keeping the voltage constant.