im a 2nd yr college student and instead of asking ai, i js want opinions from experienced people who do circuits n stuff. We have a project and we have to do one of these three: led flashing circuit, water level indicator ,ldr darkness sensor. sorry for asking this since my creative spark isnt working anymore and i cant think of any ideas. so if u guys have an idea in mind pls pls pls help me im so #desparate. first, an idea of what i was thinking is how i can apply either of the three choices in an airplane model. (the project can have all three btw). if you guys can suggest any ideas of where i can apply it please drop some. second, i dont know how to build either of those three, ive been finding stuff from yt, tiktok, ig reels, and all that stuff but i cant seem to figure out what components are supposed to be used and what their connections are. first possible question that i have is that will i be able to make the flashing led lights by not using a breadboard. i feel so dumb rn asking this but im so lost with this project and i need help. if yall can comment or dm me about this it would totally be great!

marantz 6012 has a loud buzz out of all speakers when i turn it on. as it warms up the buzz goes away. however its been lasting longer and now there is a faint buzz at all times from my speakers. im only using the RCA outs on it as i have secondary amps.

think it could be a cap issue? everythign still works onit

Hi, I'm trying to reverse engineer this spi FUTABA COG VFD, with my ESP 32. It's not broken. I'm facing problem in the logic, i don't know what logic voltage it takes,and how do I talk to the chip. The circuit on the PCB matches like 96% to a panasonic SC-UA3E CD Stereo system service manual . Fun fact when I accidentally touched the 12v pin to a adjacent pin all the elements lights up. Please help. Thank you

I was not able to find the uart connect but the recovery log on linux showed it had 3 pins ttsyS0 ttsyS1 ttsyS2

hi all! I'm disassembling an old LED monitor for fun, then I encountered this ribbon cable and was stuck for a while lol

i removed the little metal clips on the side, but that metal bar/bracket won't budge. I also didn't find any video turorial on this specific type of ribbon cable

a

Hi guys. There is an unknown SMD IC which sort of looks like a LDO or some kind of regulator but testing device shows it as pnp. What is this IC?

Hello there, I got this vfd from a dvd player and want to use it for my personal project. I never worked on vfd displays and i want to use this on MCUs like arduino, pico etc. and im wondering if theres a guide or any tips on how to use them

Hi, I’ve designed a cable tester and would appreciate a general review of the schematic before I build it. So far it has only been simulated in EasyEDA, and the relay doesn’t simulate reliably.

Description:
A two-gate CD4011 oscillator clocks a CD4017, which scans outputs Q0-Q7. Each output goes through a 1N4148 diode and a 330 Ω resistor to a cable terminal and to a transmitter-side LED. On the receiver side, LED n lights together with transmitter LED n when wire n is good, so I can detect an open wire, swapped wires and a short. Power comes from a 9 V battery through a 7805. I switch it on and off with START and STOP pushbuttons and a single 9 V-coil relay with a self-holding circuit.

I’d welcome any feedback on the whole design, especially the relay latch and the power supply.

Thanks in advance!

Hello, I need to wind some sepecifc transformers for an amplifier project, EI212 or EI210. Problem is nobody wants to sell laminations in small batches, any of yall know where you can get some?

Hi all, I'm working on a project where I intend to use a SuperCap + TPS61094 for backup power. As I don't have much experience in such applications, following are some questions. Hopefully someone can help...

• The device is powered via a USB 2.0.

• If the USB is disconnected, the device enters "low power mode".

• There is the target that the SuperCap can sustain the device for 4 days when in "low power mode".

• I have initially considered the Cap HS1025-3R8706-R, which has the following basic specs (from datasheet):

  • 70 F (+/- 20%)

  • Maximum leakage current 5uA

  • Maximum rated working voltage 3,8 V

  • Minimum rated working voltage 2,5 V

  • Minimum allowed working voltage 2,2 V

Following is a block diagram:

• Note how SuperCap allows up to 3,8V operating voltage, but TPS' closest configurable voltage is 3,7V

• When in "low power mode", lets assume a load which draws constant 75uA (derived from a worst case theoretical calculation).

• If I add the SuperCap leak current here, we reach 80uA total.

• There is no peak conspumption (there is no wake up to transmit data or anything. The device really just stays in low power, keeping track of its RTC counter)

My process was to:

1. Calculate the electrical charge in Coulombs which my load needs for the 4 days target

   • Q [C] = i [A] * t [s]

   • Q ~= 27,6C

2. Calculate the electrical charge in Coulombs which the capacitor can provide (considering worst case for everything, like capacitance being 20% off, operating voltage range of the cap, etc)

   • Q [C] = C [Farad] * DeltaV [Volts]

   • Q = (70 * 0,8) * (3,7 - 2,2)

   • Q ~= 84C

• Based on these numbers, I felt safe to say that this will be able to sustain the load for around 3 times the requirement (I can even reduce the Cap, but lets keep it as is for now for the sake of this post)

Questions

1. Does this process make sense or am I missing something?

2. How to deal with the operating voltage range of the SuperCap? From what I read the TPS docs, there is no such control configuration. How to prevent it from damaging the Cap and attempting to draw power from it even when it is around or below the minimum operating voltage?

3. SuperCap charging wise:

   • Is it OK to configure the carging current of the SuperCap to 100mA?

   • In such case, If I go from 0V until 3,7V at 100mA, and considering a 70 + 20% = 84F cap, I calculated

   • t [seconds] = (C [Farad] * DeltaV [Volts]) / i [Ampere]

   • t = 3108 seconds until fully charged

4. Any extra recommendations?

Hi I built powerbank out of 18650's in 4s4p configuration, of course with bms and the charging board is IP2368 100W (bi-directional, single usb-c).

I wanted this powerbank to have cool display for information like voltage, current etc, but I hit the wall - it appears the only good, cheap and relatively high accuracy modules i can buy are from INA family, but most of the time shunt resistors on those boards are rated for 1A max. I know I can desolder this shunt and solder other one to handle for example 10A but I read that those boards and traces on the pcbs are not likely to handle this power over long periods of time.

Right now I have standard ssd1306 display with esp32c that reads voltage from ADC by using voltage divider with capacitor to filter out garbage:

R1: 100.4 KΩ

R2: 15 KΩ

C1: 100 nF (in parallel to R2)

I applied some corrections to the program reading by comparing it out to the multimiter. It is connected directly to the positive output of the BMS.

This solution is flawed, because without measuring current voltage drop is causing my 'estimated left wh' and % of capacity remeaning to be incorrect. This can be fixed with current sensor and I also would be able to read the current flowing which is cool on its own:).

So my question is, is there a module relatively cheap that can satisfy my needs? Or I have to modify existing INA boards or maybe something different?

TLDR; I want voltage and current sensor for 4s4p powerbank that can handle at least 10-15A

Thanks for your help and time in advance.

danihek.

¡Hola a todos! Tengo una pequeña máquina de humo portátil, una LOOK Tiny CX, que normalmente funciona con una batería de litio de 11,1 V (3 celdas).

Desafortunadamente, se aplicaron accidentalmente 24 V directamente a la entrada de la batería en la placa de circuito impreso (PCB) de la máquina, en lugar de la alimentación correcta de 12 V.

Hay un fusible de 10 A entre la batería y la PCB, y se fundió. La máquina puede que se haya encendido durante unos segundos, pero no estoy del todo seguro. Ya no enciende.

Tras inspeccionar visualmente la PCB, observé lo que parece ser un componente dañado o agrietado, marcado como “LE1” / “GSJY” con un símbolo similar a un dólar. Su referencia en la PCB parece ser D2. Parece tener terminales positivo y negativo y se encuentra justo después de la entrada de la batería.

Supongo que podría ser un diodo de protección (posiblemente un diodo TVS), pero es solo una sospecha.

No tengo mucha experiencia con la electrónica, así que agradecería mucho su ayuda con lo siguiente:

Identificar este componente y su función. Encontrar su número de pieza original o un reemplazo compatible. Determinar si la aplicación de 24 V pudo haber dañado otros componentes.

Importante: No he realizado ninguna prueba eléctrica, ni he retirado ningún componente, ni he intentado ninguna reparación. Todo sigue exactamente como lo encontré después del incidente.

Adjunto varias fotos de la placa de circuito impreso (PCB) como referencia.

Cualquier ayuda o consejo será muy apreciado. Me encantaría reparar la placa original si es posible, en lugar de reemplazar toda la PCB.

¡Gracias de antemano!

It’s my first time opening an electronic. I opened up a battery powered clock. I saw these contents after ruthlessly opening the black box. What am I staring at?

I mean more so how it works electrically, like what is the interaction between signals that causes the feedback loop. The best explanation for it that i’ve heard is that the feedback loop is like feedback you give to the steering wheel when driving a car, feedback on inverting terminal is like steering back towards the center when the car drifts and feedback on the non-inverting terminal is like continuing to steer off the road.

I’m just not sure exactly how the input and output interact to produce the feedback loop electrically. Can anyone explain this? Thanks!

Nothing appears to be wrong with it. Service manual for this CRT TV doesn't appear to have any values listed so I am just curious. Thanks in advance

Hi everyone,

I'm a master's student in Chemical Engineering, and I'm trying to repair a malfunctioning CorrTest CS100 potentiostat, which is used for electrochemical measurements such as CV, EIS, and OCP.

Unfortunately, our laboratory has a limited budget, so I'm attempting to troubleshoot the instrument myself.

I have some basic knowledge of electronics, but I'm still a beginner when it comes to PCB-level troubleshooting. I'd really appreciate any advice.

1. Problem

Initially, the instrument exhibited severe noise during measurements.

While troubleshooting, I disconnected and reconnected the electrode cable, possibly while the instrument was powered on.

Since then:

• The OCP reading has been stuck at approximately −2.0 to −2.4V.

• The same issue occurs with a dummy cell connected (OCP ≈ −2.3965V).

• The measured current remains almost constant at approximately 7.38µA during CV measurements.

• Normal CV and EIS measurements are no longer possible.

• When I pressed the circular 6-pin connector, the OCP reading changed significantly from approximately −2V to −6V.

2. What I've Checked

I opened the instrument and inspected the PCB.

Using a digital multimeter, I checked continuity between the six connector contacts and their corresponding PCB solder joints. I couldn't find any obvious open circuits.

However, I noticed some residue or contamination around the connector solder joints. I'm not sure whether this is normal flux residue or a possible cause of the malfunction.

I also checked several capacitors and resistors using the multimeter, but I haven't been able to identify any defective components.

Unfortunately, I don't have a schematic or service manual for this PCB.

3. Questions

1. Based on these symptoms, where should I start troubleshooting? Would you suspect the connector, input protection circuit, operational amplifiers, or ADC?

2. Could disconnecting and reconnecting the electrode cable while powered on have damaged the high-impedance reference electrode input?

3. Since pressing the connector significantly changes the OCP reading, could this indicate a cracked solder joint or poor electrical contact, even though continuity appears normal?

4. Is it safe to measure voltages on the PCB while the instrument is powered on? How can I identify appropriate test points and the correct ground reference without a schematic?

5. Are there any recommended methods for systematically tracing the signal path and identifying faulty components using only a multimeter?

I can provide detailed PCB photographs, connector close-ups, and measurement screenshots.

I'm particularly interested in learning how to diagnose the problem step by step rather than randomly replacing components.

Any advice or suggestions would be greatly appreciated.

Thank you for your help!

It looks very burnt to me. The flyback has been arcing and so I discharged the CRT and removed it. Before I move forward with my repair attempt, is this board in need of replacement? Is cleaning a possibility, and if so, what would I use to clean it?

With this community support, I made current modulation prototype a success between 2 Arduinos, now I am planning to do voltage modulation - master switch bus 12/9 volt to sense slave adc to read data - how to protect MOSFET from switching spike, Does it can cause a problem on low baud less than 1200 baud in prototype.

What is the cap value on Ps5 model CFI-1115A with motherboard EMD-020 located on 5v rail underneath f7003 fuse right after the fuse besides the 020 IC?

i recently started training to be a computer repair technician, which has given me the confidence to open up this yamaha DGX-300 electronic keyboard i bought a few months ago. of course, being that i got it at a thrift store for around $50, it came with some issues. namely, the pitch bend knob broke off at some point, taking part of the board with it, and was just rattling around in there. this caused the sound of the keyboard to be permanently shifted by a whole step, which is less than ideal.

my worst fear was that the knob had been attached directly to the mainboard, but thankfully it had its own isolated daughter board all to itself, as seen in the pictures. i could try to find a replacement online, but that sounds costly and time-consuming, so i think i'll just remove it and see if that fixes the issue since i wouldn't use that knob much anyway. in either case, i need to disconnect this cable, which i currently have no idea how to do. any ideas?

update, 2hrs later: i've decided to cut it off. considering that, according to y'all, the only alternative involves a soldering iron (which i don't have), i figured this was the best course of action. thanks for the help!

Hey my Sanyo CDP-4300CR  only plays through my left headphone, but plays through both when i have the it halfway plugged in. Ive tried bending the metal bit in the hole out a bit, but no luck with that so thinking it may be something with the solider points? any advice would be appreciated!!!, the green plug is the headphones one.

thanks

i have a pir that outputs 3.3 v, thats no enough so i want the transistor to let go trough to 5v when it recieves the 3.3v, how do i set that up?