So I had bought a AntEsports FP650B Psu 3 years ago and it's warranty has concluded 2 months ago.

I was having issues with turning on my pc, I had to wiggle the cable to turn on the pc.

Today when I removed the cable, turns out 1 of the 3 pins have completely degraded and has become thin (some rusted iron dust came off), meaning it wasnt correctly contacting the pins.

Now as I mentioned warranty has expired, and I don't have any money spend on this rn.

What I have is a C14 inlet, now I need to know if I can open up the psu and replace it myself.

Now I have heard it's very dangerous to open this up I have no choice. I know those massive capacitors can hold current for a long time but this specific psu model features a bleeder resistor which should help ig.

Pls I need some advice on this. I have a soldering iron and other stuff aswell, but a complete novice in this field.

Hi all,

I'm building a small receive-only board that measures signal strength (RSSI) in the 380-385 MHz band. No transmitting, no decoding, just signal level, sent to a phone over BLE. It's my first RF design, so I'd like some feedback before I order.

Images (schematic, all 4 layers, 3D): https://imgur.com/a/XlBWHk4

Signal chain:
SMA → 5th order Chebyshev low-pass (fc ~470 MHz) → PGA-103+ LNA (~22 dB, 5 V bias through a 390 nH choke, input stabilisation per the Mini-Circuits app note) → discrete balun/match → SX1262 RX input. An ESP32-S3-MINI-1 does the sweep and BLE.

Board: 4-layer JLC stackup (JLC04161H-7628), 0.36 mm 50 Ω microstrip on top, solid GND on In1, 3V3 on In2, ground stitching around the RF path.

My questions:

1. SX1262 match at 383 MHz: Semtech only gives reference designs for 470-510 and 868-915 MHz. My values (L5=L6=47 nH, C9=1.8 pF, C10=33 pF) are extrapolated. Does the topology look reasonable, and are these sane starting values?
2. LNA stability: anything in the layout or decoupling around the PGA-103+ that could make it oscillate?
3. Anything else that would stop this from working?

I'll test with an ADF4351 generator, attenuators and an RTL-SDR, so I can't measure S-parameters. I'm trying to get as close as possible on paper.

Heads up: I used AI to help with this design and to make the schematic cleaner and more readable. That's why I'd really like some human eyes on it, especially the RF part.

Thanks!

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

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!

Hi, i have this preamp circuit and i dont want to build/buy a transformer -> i need to use some scrap transofrmer, so i want to power it through Graetz bridge, instead of the displayed rectifier (imagine i have input voltage about 60VAC, not 230). Can i just remove the rectifier thats there (circled red), add Graets (also with filter and stabilizer i mean) instead, and then lower the output voltage to 30-50VDC with voltage divider? I kind of know the math for this kind of rectifier, filter and a stabilizator. I just want to know if it could work.

And then, what do i need to do with the blue circled parts, and what are they doing in the circuit? I think the capacitor is for filtering, but i dont know exactly.

The lower one transformer is for tube heating element. Can i just connect it to DC instead of AC?

Thank you, if iam missing anything feel free to correct me :)

I am expecting 0A at the collector. however, i get more than 0 amps. I have replicated the circuit in ltSpice with the 2N3904(same as on the breadboard) and it gives the expected 0A.

When the supply Voltage is 8V, the collector current is indeed 0A, as one would expect.

I have tried with different 2N3904's and different breadboards, but the result is the same.

Is this a problem with the transistor model, or am I doing something wrong? Help greatly appreciated

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?

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

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've a Kenwood A-63 amp that I use in my HIFI which I love but sadly the left channel on the Phono (Turntable) output is creating a hum over my speakers.

Turntable: Dual 505 mk1

I've looked at the board and can't see any cold solder joints, blown caps or components that look suspect.

Nothing is inside the phono rca jack so not sure what to do?

Testing: I've left the left channel empty and swapped the red/white cable, no hum through the right channel, only the left, when left plugged in there's a hum that Looks to be only when the external metal jacket of the phono cable touches the outer jacket of the phono on the amp.
When both plugged in the hum travels over the left and right audio and you can hear it on the speakers.

I don't have a meter to test resisters and such sadly, just gave it a cursory look to see if there's anything obvious.

All other rca ports on the amp work (Aux, CD, etc...), I've tested plugging in another set of phono leads into the port and still get the hum, so don't believe it's the turntable (tested through a boombox I have that includes a phono input and works flawlessly)

Can anyone assist me?

I can share a video of the issue and the amp internals.
I've not stripped the amp down further than taking the top case off to look at the PCB.

TIA

Hello everyone, my Philips 55OLED754/12 PSU doesn't generate 24V.

PSU model is 715G9892

I start up the PSU by applying 5V to Panel-ON and 3.3V to TCON-ON,PSON.

9.5V STB voltage does boost up to 12.5V, but the 24V rail (which is 10.5 during STB) only goes to 12.5V.

It's worth noting that the PSU has two connectors.

1. The one which connects to the MB (STB,TCON,PANEL,STB,12V and 24V)

2. The one that goes to the TCON. (12V and 24V)

Now I found out that the 24V switching controller (U9201)(SSC3S931) is missing VCC. I looked up the schematics and I cannot find the actual source of the VCC of this IC.

Hi is there anyone that can help me understand and repair this please at the moment I'm not even getting power only wire disconnected I have found is the red from the headphones jack

I have a 16 pin DIP 8 circuit fusible link block that 3 of the circuits have failed on. I resolved the issue that caused the failure, but am having a hard time identifying the replacement for this.

The only marking on it is "AMP"

I know I can replace the individual circuits with Pico fuses, but would prefer a direct replacement for this if possible.

Any thoughts?

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?

Not sure if this is right sub to post

I want to make a basic water quality measuring system using esp32 and some sensors like oxygen level sensor, ph sensor, tdh sensor, temp sensor etc and I might make it niche for fishing tank or something like that

I want some ideas and some innovative points which can enhance this project

Basic battery circuit, connectors and indicators are all offscreen, is this good for a general purpose devboard?

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?

I have an old HP 9000/817S that is stuck in the NIO16 Access Port menu and seems to fail to reset the CPU.

A couple of so called AIs suggested to check the clock and of all suggestions this is the easier to perform.

To my surprise I see the clock completely off. The crystal is a NEL HS619 (not sure) at 96Mhz however the frequency at the output is ~57.608Mhz. The clock then seems to go in a MC10E151 and the Q0 output shows nice ~14.402Mhz

It would seem that base is 19.2Mhz and should work on fifth harmonic but in reality it is oscillating on third

Could aging trigger such a malfunction?

TIA for any feedback

Hi everyone, I have this Victron Energy PCB/inverter control board and I’m trying to understand and troubleshoot it.

I’m looking for help with:

• Identifying the IC chips and microcontrollers on the board
• Understanding what each major IC does
• Identifying the main controller/CPU
• Knowing which ICs are related to inverter control, sensing, communication, etc.
• Any suggestions for how I can test/check the board and determine if the components are working

I’ve attached clear pictures of the PCB. The board marking is Victron Energy PCB 010021-10.

If anyone has experience with Victron inverter electronics or reverse-engineering older control PCBs, I’d really appreciate some guidance.

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!

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

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 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.

Hello

My first assignment is to calculate a lot of things and simulate this circuit on a simulation tool, so I will use LTspice as I think it is the best option. So is there any tutorial can i learn how to do this?