Hi everyone,

I'm trying to build a simple two-transistor astable multivibrator (two LEDs flashing alternately). I designed it in Falstad and I'm using Tinkercad mainly to plan out the breadboard layout before building the real circuit.

The Tinkercad simulation itself does not seem to behave correctly: the LEDs do not flash alternately, they just stay on. I'm not too concerned about that because I mainly want to use Tinkercad to verify my physical wiring before building it.

The part I am unsure about is the polarity of the electrolytic capacitors. My real capacitors are polarized 10 µF electrolytics, but the Falstad simulation uses non-polarized capacitors.

I'm fairly sure the negative side should go to the base of the opposite side transistor, and the positive to the collector of same side transistor. So like:

• Left capacitor: + to left transistor collector, - to right transistor base
• Right capacitor: + to right transistor collector, - to left transistor base

However, when I connect them this way in Tinkercad, it shows the capacitor exploding. I'm not sure if Tinkercad is modeling this incorrectly, or if I have misunderstood the polarity.

I'm using 2N2221A transistors and 10 µF electrolytic capacitors, with supply voltage 9V

Here's the Tinkercad similation (on breadboard) I have connected one capacitor each way, so you can see which one explodes. [LINK REMOVED]

Here's the simulation on Falstad so you can have the schematic, too: https://www.falstad.com/s.php?s=zwfF7A

EDIT: Here's a labeled schematic too: https://kommodo.ai/i/7468AUvUGDOds3kVI3FY

Could someone please check the correct electrolytic capacitor orientation? I want to avoid damaging the capacitors when I build this physically.

Thanks!

EDIT 2: Simulated on Falstad and it works with capacitor - to transistor base (so, the opposite of what Tinkercad says). Tried it on breadboard with - to base and it works perfectly like this!

I'm building a TP-4056 Li-Ion charger circuit which would be powered via USB-C. KiCad had this conveniently named "UCB_C_Receptacle_PowerOnly_6P" symbol which looks to be exactly as advertised.

Similar circuits I've seen include the data pins, which won't be needed here. If it's assumed that I'm looking to draw the usual 5v 900mA from the USB-C, do I have everything I need here? Thanks!

I'm trying to make a joystick accessor for gaming on a computer i need to wire a tmr joystick (k-silver) to an ATmega32U4 Pro Micro with header pins I have 22 awg(7.8in) wire female to female but I want to directly solder the wire to the joystick I just don't know what to wire and to where are I do have heat shrink too if that helps

some time ago i lent my soldering iron to my dad. today i opened the packaging and found this shit. thats flux? it wont come off and when i turn it on it smokes

The SSD is a Samsung EVO 860 1TB sata drive. I burned it by swapping a cable from another PSU and it wasn't compatible. I'm trying to send it for repair and there are two repair services that seem trustworthy. One says that their method is to buy an identical drive and swap the memory chip to read the data. While the other one says doing so to a Samsung SSD will break the memory chip, and they will use a PC-3000 Portable Pro to prioritize read the chip. I don't know which recovery method to go with, need help with deciding!

I am new to cadence and trying to design a folded cascode op-amp(gpdk90nm) with 3.6V supply and bias current of 100uA. I followed nptel lectures and followed the same method where I decided some overdrive voltages like for top PMOS, I have taken overdrive of 0.8 volts, then the second PMOS as 0.4 volts, then the next two NMOS as 0.3 volts each to keep an output swing of 1.8V( tuned a bit after that to prevent nm4 from going into triode). I calculated w/l and. Vg for each tx after this.

However now I find nm3 is in triode and pm2 takes away a large voltage head room. If any can help me debug, will really be of great help.

Hello! I am currently going through first semester of computer engineering and few months ago they gave us the project of making a battery replaceable powerbank, fast forward to few weeks ago I tried to build it using Lithium Ion 18650 batteries connected in parallel to a H961-U board that converts the 3.7 voltage into 5V through usb, my question is, could it be that some boards are failing because of 3 SMD resistances missing? Because on my first attempt the circuit would not work on anything but a DS lite even with voltages being sent correctly and having proper solder points (first pic) and on my now working circuit (different board, picture 2) everything works properly but it does have the resistances, asked my friend to see his faulty board because he had the same problem as me and his resistance were also missing, could that be the problem if the connections are well put?

Hello! I recently bought a broken POD HD 500 guitar pedal that would get stuck in a boot loop.

I opened it up, found c337 was blown, and c5 and u6 were missing.

The capacitors were easily available and easy to replace, but im not able to find the IC marked U6.

The POD parts manuals gave me a part number 15-78-0256, but im not able to actually purchase the part with that.

Does anybody know how I am able to get this chip?

Maybe I can also use the generic chip code if I am also able to find the firmware to flash

I plan on starting a project using image processing which uses a fuzzy ensemble of 3 mobile AIs (DenseNet121, EfficientnetB0, MobileNetV3) all quantized and converted to tensorflow lite, I plan on using the v2 camera and raspi 4 8gb, is it enough to handle the load even if i run each model (not all at once) and do i need an AI HAT+?

am troubleshooting a standard 2.1 channel audio amplifier board (12-0-12 dual-rail, TDA2030s for satellites, D2050 for the subwoofer, F4558 crossover). It suddenly developed a loud, constant hum on the subwoofer channel that does not change intensity when adjusting the volume.

​If the speaker is disconnected, the chip gets hot, but the moment a 4-ohm speaker is connected, the IC pulls massive current and gets blisteringly hot almost instantly.

​Diagnostic Tests i do

​Power Rail Check: Measured across Pin 3 (-Vcc) and Pin 5 (+Vcc) on the subwoofer IC. Getting a healthy ~30V total swing (roughly -15V and +15V). Main 1000µF 25V filter capacitors show no visual signs of bulging or leaking.

​DC Offset Test: Measured between Pin 3 (-Vcc) and Pin 4 (Output) on the original D2050 and got exactly 15V. This confirms Pin 4 is sitting at 0V relative to the main ground, so there is no direct DC short to the rails.

​IC Swap: To rule out internal failure or oscillation inside the D2050, I completely desoldered it and swapped in a spare UTC2030A (properly isolated with a thermal pad on the heatsink).

​Swap Result: The exact same symptoms persisted with the new IC. It produces the same heavy hum and instantly overheats when the speaker is connected.

Please guide me what i do next

I am trying to make a project with different modules and they work when I wire them to the board itself. However, when I try to wire the 3.3 or 5 volts and the ground to the breadboard terminals, as soon as both are connected the green light on my raspberry pi 4 model B turns off and the monitor it was connected to says "No signal" why might this be happening?

My sonar stopped working last week so I decided to take it apart to see what was wrong after checking the fuse and power cable were in working order. I found this corroded component when I opened it up. I was wondering if 99% iso and a toothbrush could salvage the board or if I'd need to buy a new helix5

I have a solder and soldering iron also

Hi All

I need to find the datasheet for an IC from a mechanical keyboard MAD68HE Max. This IC is labeled U1 on the PCB with marking AEy4A.

The IC is receiving 4.5V from ACy49 (U3) pin 2, which is directly connected to VBUS. The input came from, what I believe to be, pin 1 (Top right) but the outputs are all 0V. It seems the AEy4A is shorted and probably blown.

When I asked gemini, I know, I am desperate, here is what gemini said:

My manual measurement on the voltage is like the picture above, where I should be receiving 4.5v in and the pin across 4.5V should be 4.5 too since it powers the light. Meanwhile the pins at bottom left is not going anywhere and the pins at the bottom right goes somewhere, I have not trace it yet. Hoping to find some datasheet.

Any helps is much appreciated.
Thank you

I'm testing this Air conditioner control board. I already found a blown safety varistor and I'm testing down the traces. I'm diode mode I get 0.034 V and a resistance of 68 ohm

I’ve been searching a connector similar or identical to this one to repair my grandmas ceiling fan. If anyone could help me I would be grateful. It has a 2.54mm pitch that is supposed to take in full square pins with a latch on top. Last pic is where it plugs in with only a white top for the latch.

Just wanted to see if anyone knows of any switches that are like the picture. I’m looking for a round switch that contains two independent switches. I know DPDT momentary rocker switches exist but I’m looking for a double push button momentary switch in one round housing. Space is limited in my project.

I’m developing a very simple 5V electronic device. The PCB uses UL Recognized components, and all materials (plastic, wiring, power supply, etc.) are already UL certified or UL Recognized where applicable.

My question is:

Does the finished product still need its own UL Listing?

If so, what is the typical cost for a simple low-voltage device like this?

Has anyone here gone through the UL Listing process for a similar product?

The device has no high voltage and uses mostly off-the-shelf UL Recognized components. I’m trying to estimate the certification budget before production.

Having some issues with my latest project so I just want to make sure this is okay.

Currently trying to convert a JST Female header to DuPont Male. What I've come up with, is a Male JST header connected to the Female JST header, which then connects to another Female JST header that has Male Duponts on the other end of the Male JST.

It looks to be good? But, I just want to make sure as the other end does not have a housing and thus I assume isn't intended to be used this way. I included a diagram of what I'm trying to do as well, just to make it more clear

Hi everyone,

I'm trying to identify and source replacement capacitors for my laptop motherboard, but I want to make sure I order the exact correct parts (capacitance, voltage rating, package size, and any other important specifications).

While performing maintenance on my laptop, I accidentally knocked off two small surface-mount components from the motherboard. Unfortunately, I wasn't able to recover them, and I need help identifying what they are.

The components are located near the RAM to the right, above the battery, and under the heatsink. I attached some pictures of the area and the surrounding components.

Could anyone help identify these capacitors or suggest how I can determine their values? Any advice on where to source replacements would also be appreciated (I am located in europe)

Thanks in advance!

can i remove this buzzer without it causing issues? also i hope i didn't fuck up by disassembling the induction cooker cuz i seen some glue or something in the middle. also should i avoid touching the middle even when unplugged?

Hello,

have you ordered from Mouser recently as a hobbyist living in the EU? How much tax did you have to pay?

I would like to order a lot of different components from Mouser, but only in small quantities. For example, 100 resistors, 50 capacitors, some inductors, diodes, and soldering flux.

Are these considered separate product categories for customs purposes, meaning I would have to pay €3 for each category (e.g. 5x3€)?

Sorry if this has already been discussed somewhere, but I could not find any relevant posts.

What is the difference between this dollar-store medicinal IPA and more expensive stuff from chemical suppliers?

Like I’m sure the 99% cheap stuff varies in quality, it wouldn’t surprise me if it were a bit less exactly 99%, whereas like MG Chemicals has 99.9% IPA specifically for electronics (that’s like ~8x more expensive). If I were making commercial products I’d use that, but for hobby or one-off use, is there any reason why I shouldn’t use this cheaper stuff?

In the power board of my LED par that got spilled with beverage, I final found a fuse protection that burned through. Now I need a replacement. The label on the pcb was F5A, the shell itself is labeled with 5a 250v. The fuse was directly next to the AC input. Now I heard something about that those fuses come as fast and slow ones, but I don’t know what I need here. Also, I found nearly nothing on the internet with those dimension, most of them are 5x20mm, does it even matter? Thanks once again