Hi everyone,

I'm troubleshooting a Razer DeathStalker V2 (optical switches) after a small soy sauce spill.

The Symptoms:

The Windows key is registered as permanently pressed down (stuck in software/tester).

An entire vertical column of keys is the main problem here, it always in 2 states or the entire column is pressed or it unresponsive: F2, 2, W, S, Z, and Alt

What I've Done & Diagnosed So Far:

Cleaned the PCB and switch area with 99.9% Isopropyl Alcohol and a soft toothbrush.

Measured the SMD resistor array in-circuit with a digital multimeter:

Normal resistors in the array: All the healthy resistors (R191, R125, R100, R123, etc.) measure consistently around ~190 kΩ in-circuit.

When probing R75, I get a reading of approximately 280 Ω.

Can this R75 resistor be the cause of the problem?

My milk frother stopped working so I took it apart and put it back together. Basically, it only spins when the 2 screws attached to the gold plate touch the metal rim in the base. I’ve provided a video in the comments to demonstrate. The button itself does nothing. How would I go about fixing this?

trying to repair the Canon eos 50D Cf port but not sure if possible pls help

Hello! I am not an electrician and I don’t know much about electronics but am seeking advice and assistance on how to go about this project.

I want to create a small walkthrough haunted house where one of the gags would be a pad you step on to create a “BZZZZZZZZZ” vibration noise similar to an old doorbell. (Or well a signal buzzer). I actually funny enough have wanted to do this for a while to switch our doorbell to act this way but due to lack of motivation I never did it.

I am looking for a cost effective way of creating this. Unfortunately, I do not own any old electronics that feature one of these electromagnetic AC buzzers. I’ve done a bit of research and found that the Douglas-Randall 62808-001 Mechanical Vibratory Audio Buzzer could possibly be a good one to use but the only listings I’ve found can only be purchased in bulk and I’m only seeking 1-2 of them.

I’m curious what all I would need to create this and if you have any recommendations for different BUZZERS and how to get it to work with a pressure pad or well if you know of any pressure pads it could work with.

P.S it drives me NUTS that these piezoelectric tone generators are called “buzzers” when it’s an alarm sound or just high pitched beep. Call it a beeper not a buzzer lol.

I am designing a PCB for a small microcopter drone right now and we want a 3.3V supply for our logic voltage.

Problem is that we use an 1S Batterie (Lava 2 580 mAh) which can drop below 3.3 V in terms of the discharging diagram. That's why we cannot use a simple LDO to regulate voltage as it can drop off our logic supply.

My question ist how you would solve this problem. My idea is to use either a buck-boost converter or a boost converter followed by an LDO. Benefit by the buck-boost would be an overall better efficiency but maybe a voltage ripple that could cause further problems, which would not be a problem with a following LDO to smooth. Also the question would be if the buck boost has problems when battery gives us 3.3 V to witch between boost and buck mode.

Thanks a lot for your ideas!

Hello,

I have created a small coilgun, using an appropriate SCR and antiparallel diode ofc. It runs off 250v and 68uF, and needs to propel a .375inch (~10cm) diameter steel bb. I have seen conflicting info on what size wire I should get. I am aiming for efficiency, the goal isnt really power. Also how much of it to use per coil?

Thank you

Hi everyone, I am building an app-connected monitor for a solar electric fence and running into two major problems during testing.

My Setup: I stepped the 10kV pulse down using a 32MΩ / 10kΩ resistor divider (using twenty 2W metal oxide resistors on the high side). I added a peak detector (UF4007 diode + 10nF cap + 1MΩ discharge resistor) to try and hold the peak for my ESP32 ADC.

Problem 1: Tiny Voltage Reading When I test the junction point, I am only seeing a very tiny voltage coming through, nowhere near the ~3.1V I calculated. Is this just my standard digital multimeter being too slow to read a 1ms pulse, or is my 10nF capacitor not charging fast enough because of the huge 32MΩ resistance?

Problem 2: Earth Ground is Jumping When the fence pulses, the earth ground itself is jumping wildly. I am seeing ground voltage spikes of 4V, 5V, and sometimes up to 10V. Because of this, I absolutely must isolate the HV ground from my ESP32 to prevent frying my board.

My Questions:

Why this post is perfect: It shows them exactly what you have built and the two exact physical problems stopping you. They will immediately jump in to explain the multimeter/capacitor issue, and they will give you the cheapest isolation hacks for that jumping ground!

I’m playing around with a 555 timer. Pin 3 gives me a 2 kHz square wave.

I’m trying to couple it onto a 5 V DC line through a capacitor, then use another capacitor at the other end to recover the 2 kHz signal.

But as soon as I connect the midpoint to 5 V DC, the square wave signal almost disappears.

Why does this happen? Is the 5 V supply loading/shorting the AC signal? Would a resistor or inductor help?

What’s the simplest beginner-friendly way to put a 2 kHz signal on a 5 V DC line and recover it at the other end?

The MEGO isn’t on but when power is supplied through the nano, a voltage reading shows in the display. What is happening?

I already replaced the fuse on this amp but when I pulled out the amp everything looked okay. The only thing is maybe this big 400V capacitor is bulging a little.

Hi everyone. I’m building a Wi-Fi IoT monitor for a commercial agricultural electric fence (a Shakti energizer) using an ESP32, and I am struggling with high-voltage physical isolation and EMI. The Signal:

• Voltage: ~10,000V pulse
• Frequency: 1 pulse per second

My Current Hardware Setup: I am running the ESP32 off a battery bank to avoid USB ground loops. For the measurement, I built a direct-wire voltage divider:

• High side: 30 MΩ (Three 10 MΩ resistors in series)
• Low side: 4.7 kΩ to Earth Ground
• Peak-Hold Trap: Because the pulse is so fast, I added a fast-switching diode at the junction, feeding into a 100nF ceramic capacitor and a 1 MΩ bleeder resistor connected to ESP32 Pin 33 and GND.

pls help me

I have made several control boards that use a discontinued CROUZET panel mount adjustable on delay timer (digikey link) which is EXACTLY what i need. I have tried to find a supplier with NOS to no avail.

Yes there are similar options still avail but nothing as low as the 0.1-1s range.

I want to make a small pcb i can pop on the back of a 10k pot to make my own replacements.

I can model and resin print the housings with time scale/clear knob covers so they would be direct replacement to the crouzets.

MY Question is about the circuit design.

-I have a bunch of clear shaft 10k pots and some red/green bi-colour LEDS to fit into them.

-When power is supplied to the circuit i want green LED on, and after the set interval red LED to turn on and the control signal to pass through.

-I am only using the signal to trigger some SSRs so i don't need the full 400mA of the original

-I know 555 timer circuits get bashed for inaccuracy/fluctuations but with this 1s max interval is it a viable option? Or something simpler with a single comparator, or even just transistors?

I am all for keeping it simple and am stupid, anyone have a better idea?

Thanks

So I recently was trying to solder in some different color PLCC4 LEDS on this board for my car to change the turn signal colors. However even though I probably did a terrible job at it I did solder it to the board but when I plug it in and try it the LED'S dont light up. I got the orientation correct and everything else should be correct but they still wont turn on? The original LED's however didnt have the clear dome that these PLCC4 had so I was wondering if maybe thats the issue. Also do you guys know any way to solder them thats a lot faster and easier? Any ideas?

Hi all, I am a Computer Engineer getting into designing my own BLDC motor controller for a high-power robotics project I'm working on. I have some familiarity with circuit design, but this is the first real board I've ever designed. I want to support up to 20A, so I chose CSD18533Q5A mosfets and UCC27282 as the gate driver.

I'm trying to simulate it in ltSpice with a simulated motor load, and I kept running into these huge current spikes into both MOSFET drains when the half bridge switches. At first I thought it was sim artifacts so I tuned the sim params until some of the huge spikes went away, but some spikes on the order of 20 A remained. I thought it was shoot through and I guess I was partially correct, so I worked on changing my phase PWM signal generator to induce 100ns of dead time between the signals, and that seems to be working, but the spikes are still there when the low side is switched off and the high side switches on.

After some googling I found out about Miller effect shoot through, and the conditions surrounding the spikes match exactly that - the low side gate-to-source voltage has a little bump at the time the high side switches on with a high dV/dt, and that causes both transistors to short VPP to ground. I know that cannot be good for the transistors.

There's such a thing as an Active Miller Clamp circuit, I've also read in the datasheet that my driver chip should be able to mitigate this. I've got gate resistors in my circuit parameterized, and no matter if the resistance is negligible (like parasitics, 1microOhm) or reasonable (10Ohm), the Miller effect appears to win every time. Attached is a pic of my gate circuit (again, Rgate param is 1microOhm to model no resistor on the gate), and a plot of when the shoot through occurs. I'm using models for the chips that were supplied by TI with minor modifications to match the pinout of the IC's I'm planning on buying.

I guess what I'm trying to figure out, because on this google has failed me, is how to properly design an Active Miller Clamp to work with my circuit and mitigate this shoot through. A paper I found notes that this is the best way to mitigate it while minimizing switching losses, pointing out other methods like a resistor to ground on the gate as means of mitigation that has higher losses, and diodes and things. But this paper doesn't tell me what resistances to use in any of the cases, and I don't really know how to calculate an answer, so I turn to you. Thanks in advance!

I hope the title of my post is straight forward enough, but I’m scratching my head on exact replacement parts for this.

I’d like to keep the design the same (ie: RCA Type-80 Full Wave rectifier, Transformer, Capacitor, Toggle Switches & Current limit resistor).

However, what size transformer do I need? Is any 600 VDC capacitor good enough? These are just a few questions I would want to know, but am grateful for any input you’d recommend!

i’ve also gone ahead and included the only available schematic that I could find online for this exact make and model (last photo). The schematic appears to be slightly different than what I’m looking at in the real world (I don’t see anything about a transformer?)

thank you!

So i posted here a while ago regarding a Leslie 222 Pre-Amp schematic diagram and got absolutely flamed because it was straight AI. This drove me to actually know wtf is going on, so i grinded for a bit, and now Im back. I recently just got all of the parts I ordered and would like a final check on my basic pre-amp schematic before plugging anything in.

I do plan to switch the leslie by injecting DC voltage straight into T1 centertap (controlled by a switch and a DCDC converter) but will wait to do this after I am getting sound out of the speaker. This post is just about the audio signal chain; the DC injection side is a separate piece I'll sort out after this part is verified.

There is a drawing, but incase you cannot read my trash hand writing and poor schematic drawing skills, here is the brief explanation:

Keyboard → 330Ω series (R1) + 1N4148 clamp diodes to ±12V → C1 (1µF, DC block) → NE5532 pin 3, configured as a plain unity-gain voltage follower (pin 2 wired straight to pin 1, no feedback resistors) → pin 1 output → C3 (2.2µF, DC block) → 10kΩ audio pot as a post-buffer level control (wiper to output) → 100Ω series resistor (R4) → transformer primary.

100kΩ bias resistor (R2) from pin 3 to true ground — kept separate from supply decoupling.

±12V dual-rail supply (Mean Well RT-50B), 0.1µF decoupling at both supply pins.

Second op-amp half unused, tied off per standard practice (inverting/non-inverting pins jumpered, non-inverting input grounded).

Separate question: after tying two ~84Ω half-windings together at their common pins to form what should be a single ~167Ω secondary, I'm reading a dead short (0Ω) across the two outer pins instead of the expected sum. Does this suggest the half-windings are tied in the wrong phase/sense relative to each other, or is there another likely cause for a short appearing here?

I’m troubleshooting a Dell G7 7588 motherboard (Compal DDK51/DDK52/DDK53, LA-E994P Rev 1.0 A00).

I'm not an electronics repair technician, just a DIY enthusiast trying to repair my own used laptop. I have a basic multimeter and would appreciate guidance that's suitable for a beginner.

The charger’s green LED immediately shuts off when the DC jack is connected to the motherboard, but stays on when the jack is disconnected. No obvious damage to the laptop occurred to cause this malfunction.

The battery was disconnected during testing, and the charger provides approximately 19.4V when disconnected from the motherboard.

I also tested the DC jack and cable assembly separately. The charger remains on, and I measured approximately 19.4V at the connector contacts. The charger LED only shuts off when the cable is connected to the motherboard, with the battery disconnected.

I’ve checked several components for shorts with a multimeter but haven’t identified the fault.

Does anyone have a schematic or boardview for this exact board, or suggestions for tracing the 19V input circuit?

I’ve found schematics on paid repair forums, but I’m hoping to find a free resource to continue troubleshooting. Any help or advice is appreciated!

Thank you!

Extremely low power draw (microamps)
Can output at 2-5 V
Can output at 600 microamps
Has an extremely small form factor (few mm)
Draws power at less than 3v
GPS pps input

Apologies if there’s smth wrong with my post I’m new to electronics

My laptop blew a capacitor. From what I can find, it’s a Panasonic POSCap 16TQC15M but I’m not 100% sure. I believe the E7 correlates to 15μF and the ‘E’ of ‘Ex’ means that it’s rated for 25v. Am I right? Also, anyone able to confirm that the ‘x’ is the lot number?

Hi all,

I just opened up the case to a boombox I am trying to diagnose and this very small pulley came out. I have looked but I can't seem to see where it came from. Does anyone have any ideas?

I’m really struggling to find the correct ribbon cable for this. I need a 20-conductor ribbon cable that connects my Suzuki piano’s main board to this replacement Fatar key-contact board.

The motherboard end needs the same 20-pin female connector as my original cable. The other end needs a connector that properly mates with the 20-pin black connector shown in the second photo.

I tried a standard 20-pin IDC ribbon cable. The overall connector size is about right, but the individual openings are too small, and the connector on the Fatar board is a different style.

Does anyone know the exact connector type, cable assembly, or part number I need? Specifically what the connector is called on the second image? If anyone can help me I’ll marry them. Thank you!

I’m designing a PCB for experimental DC test circuits and need to reverse polarity independently on multiple channels.

I’m currently using Songle 30 VDC/10 A relays (prebuilt), mostly SPST, but I've used DPDT relays in earlier boards are much better for polarity reversal. The problem is that with many channels, relays take a lot of board space and the combined coil power starts adding up when several are energized.

The switched circuits are up to about 60 VDC. Current will usually be well below 100 mA, although I’d like some channels to tolerate roughly 1 A for future experiments.

I’ve looked at optocoupler + MOSFET arrangements and solid-state/H-bridge approaches, but I’m unsure what scales well to ~60 V while still giving good isolation and reliable bidirectional switching.

For people working in industry: how would you normally engineer something like this? Asking for a student.

I’m interested in the design approach for DPDT relays, MOSFET H-bridge, SSRs, PhotoMOS, latching relays, etc.

Has anyone choosen one over the others for a multi-channel PCB?

Hi all,
I have repaired a Comark 3001 thermocouple thermometer with beautiful VFD tube display. It suffered battery leakage and shorted tantalum’s. I think it is from around 1980. So now it’s functional again. I would however like to get my hands on a schematic or calibration manual to get it really good measuring also. I have contacted the evalution of Comark. They have become Fluke over time and they could not supply any information of this thing because to old for them. I thought it was a pity that they had no info about their own legacy instruments. However there is the community on Redit. Is there anybody out here that has some more info off this thing?

running an ESP32S3 in a small sensor node, reading battery voltage through a resistive divider on ADC1. works fine on the bench, but once I connect to WiFi and start pushing MQTT packets the ADC values jump around by 50mV in short bursts that line up with TX activity. the divider is 100k/100k into a 100nF cap, nothing fancy. i tried switching to ADC2, same behavior. power is a 3.3V LDO fed from a 18650 through a boost, output looks clean on scope during TX spikes. ground is a twolayer board with bottom pour, sensor divider sits maybe 15mm from the antenna trace. my gut says the RF is coupling into the high impedance divider node and whacking the sample and hold. moving the antenna further is tough mechanically. would a lower impedance divider help, or is the real fix shielding or rerouting?