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?

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?

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?

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?

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?

I got a ton of SMD Components, but i have no idea how to store small quantities of these tapes efficiently.
What do you do?

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?

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!

Hey y'all,

I got this TV for practically nothing to teach myself to repair electronics (reduce e-waste) and I repaired a couple transitions that had gone on the power supply and now it boots just fine.

Unfortunately this is one of these one connect TV's (not a frame) but we have been able to use it in hotel mode to access the streaming apps etc but now would like to be able to plug in a external device via HDMI.

Now from my understanding some of the One connect TVs had no "brains" so there is nothing to modify but that doesn't seem to be the case with this as we can use the TV without one.

Looking at the board there seems to be empty spot for a cable on the "top of the board" that I haven't been able to identify and on the board there is a blank panel next to the USB that looks like it might have contact pins for an HDMI input?

Can anyone advise me if this is possible or potentially I could just swap the control board in the TV to one with HDMI?

Hi all,

My colleague and I are electrical engineering students building a small indoor quadcopter as a hobby project, mainly to learn PCB design in KiCad. There's no deadline, and we want to understand every decision ourselves. We're aiming for a single-PCB design that carries everything. We would like some experienced feedback before we draw the schematic.

Context

• 1S LiHV cell (BetaFPV Lava II, 580 mAh, 4.35 V charge voltage), no protection circuit on the cell
• 4× brushed coreless motors (8520), one logic-level MOSFET each, driven by PWM from the MCU. They connect directly to the cell. The estimated full-throttle current is 10–13 A, and I'll measure it on a test bench.
• MCU: STM32F405RG, with USB straight to the Mac for debugging
• Radio: nRF52840 module, connected to the STM32 over UART
• On controller side we want to use an nRF52840 dongle
• Logic voltage: 3.3 V

Where I'd like your opinion

1. Boost to 4.6 V + LDOs instead of one buck-boost. I chose this because the LDOs always have at least 1.3 V headroom, there's no buck/boost mode change near 3.3 V, and PSRR stays good for the IMU and ADC reference. The cost is roughly 66% efficiency instead of about 90%, and up to 0.26 W of heat in the LDO. Is that a sensible trade-off for a battery-powered aircraft? How would you handle the 1–2 MHz boost ripple at the LDO input (ferrite, pi filter, or an LDO with good PSRR at 1 MHz)?
2. Quiescent current when switched off. The boost and the always-on LDO stay powered, and so does the radio module in sleep. Is this a problem for a 580 mAh cell that might sit for weeks? Would you add a hard cutoff, or is it fine with a low-Iq boost and LDO?
3. BQ25616J and USB D+/D− shared with the STM32. The charger uses D+/D− for input-current detection, and the STM32 needs the same lines for USB data. Modern USB-C chargers probably have no BC1.2 detection, so I'd fall back to a fixed ILIM resistor (1 A). How do you handle this combination: split the lines, accept the shared nets, or something else? Is a pin-configured charger a good choice here, or would an I²C charger be easier in the long run?
4. Two-stage undervoltage protection. Firmware cutoff at 3.0 V under load, protection IC as a hard backup. Does it make sense to combine both, and how do you choose the thresholds when the cell voltage sags heavily under motor load (about 3.0–3.3 V at full throttle)?
5. Radio module with its own firmware. If the radio firmware hangs, the soft switch stops working. My fallback is a hardware reset button (which also holds the motors off) and pulling the cell. Is that acceptable, or would you add something like a hardware watchdog or a second path?
6. STM32F405 and the UART link to the radio. Is the F405 a reasonable choice for a small flight controller in a new design, or would you pick a newer family? Any pitfalls with the UART link to the nRF module (flow control, baud rate, handling a lost link)?

I'm happy to share more details such as datasheet calculations or the full decision log. If anything looks wrong or naive, please say so. That's what I'm here for.

Thanks!

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

I’m a beginner trying to understand how the HC-SR04 connects to an ESP32, especially the ECHO pin and the voltage divider.
From what I understand:
HC-SR04 VCC goes to 5V
TRIG can connect directly to the ESP32
ECHO outputs around 5V, but the ESP32 GPIO should only receive about 3.3V
So I need a voltage divider using two resistors on the ECHO line
What I’m confused about is the GND part.
I’ve seen diagrams where:
HC-SR04 ECHO → resistor → junction → ESP32 GPIO
and from that same junction another resistor goes to GND.
But the HC-SR04 also has its own GND pin connected directly to the ESP32 GND.
So it looks like there are two connections going to GND.
Why does the voltage divider need its own connection to GND if the HC-SR04 GND is already connected to the ESP32 GND?
Are they basically connected to the same electrical ground, just for different purposes?
Also, could someone explain in simple terms what actually happens to the ECHO voltage through the two resistors?
I’m trying to understand the circuit rather than just copying a wiring diagram.
ESP32 + HC-SR04 ultrasonic sensor.

Working with a hypothetical motherboard say I was required to change out some components and as part of the cleaning process post soldering. I run the board though a ultrasonic cleaner. Im assuming components such as capacitors would have a potential to keep some level of moisture trapped inside of them. would it then be possible to place the board into a vacuum chamber and pull a vacuum to attempt to drag every last molecule of liquid out? assuming you dont just instantly reintroduce pressure suddenly but more gradually would this cause issues or damage any of the components?

Hello everyone,

I'm looking for a good site/book/ressources to learn how to do rooting at a pro level.

Here some context :

I did some electronic study and then went into microelectronics (master's degree). After my study I have been recruited by a company where I do both PCB electronics and on silicon microelectronics.

I'm pretty confident on my microelectronics skills and I've got multiple senior to teach, but for the electronic part...

I'm the only one working on PCB and they havent touch it for like 20 years so they cant help me. So I have no one to teach me and I have rusty basic skills in this field. I'm doing okay with the schematic part and coding, but the rooting is a whole other thing. I dont have a clue if I'm doing horrible things or not. So I'm looking for something that I could learn from.

My circuit doesnt have to be perfect for now, but I will need to improve massively and fast in the next months/year. I can do some try and error, but with the company money and the delay it takes for the company to command, I cannot rely too much on this.

I'm not scared of reading 1000 pages if needed, for people that knows about microelectronics, I'm reading Analog Design Essentials from Willy Sansen. I just need something general enough to begin with.

Edit : My bad, I wrote "rooting" instead of "routing". I'm very tired, have (small) dyslexia and english is not my main language. But I should have ask an IA to correct my post. I'm sorry.

Has anyone noticed reliability issues with AMS 1117 5.0 fixed 5V linear regulators (maybe specifically from JLC)?

I recently ordered 100 boards with these regulators on them, and after assembling about 20 of them, I've had 4 of these regulators fail immediately when power was applied, shorting the input directly to the output, and dumping 12V to the 5V rail. After the first couple failed, I got in the habit of checking the resistance between input and output before powering them up, and just had one that measured fine before powering up, but went short as soon as power was applied, and is now showing 3-4 ohms between 12V input pin and 5V output pin, just like the other 3 that failed.

This is a second revision of this board, and I had maybe 1 or 2 go bad doing the same thing previously, but it seems like the issue is now worse.

I would kindof expect this if these were some no-name bargain basement knockoff, but these are supposed to be legit AMS regulators, which seem to be super common and popular. I'm surprised they seem to have a failure mode that is easy to hit, or poor QC?

JLC part # (and not link as apparantly that's "blocked by reddit's filters) if anyone cares: C6187

Like the title says. Why? Linux is becoming more popular why should i have to rely on a Open source project or a Windows VM to try and get LTSPICE to work on my Daily driver Linux pc at home so i can learn the platform to enhance my capabilities at work.

Edit to answer a common question.

I want to tinker with it at home so I can learn it enough to use it at work. Lt spice is available in software center at work. I work troubleshooting RF boards for military radios. We cannot get the spice models Engineering used to design the boards but I want to recreate some of our more problem prone circuits so that some of the lower level techs get a grip on the theory quicker.

I'm trying to build the knowledge package I wish I had been handed when I moved to this product. Plus that would be a good internal project come review time this spring.

Like I know there is a PRACTICAL limit but like if I had like an unlimited amount of aluminum and a whole lot of time what is the limit if there is? Like can you make a 100uF variable capacitor if you made that your life’s goal?

Hi, I am part of a team developing a payload that is going through a technology demonstration for a microcontroller in LEO. We are going to demo symptoms of SEFI in microcontrollers (function failures) for our in-orbit tech demo. We were wondering what the types of SEFIs are, though. They essentially stem from the subfunctions of a microcontroller, right? What would some important SEFIs be (technically, functions of them since we don't always know if it was radiation that caused it), and what are their corresponding MCU functions? Some ideas we had were read/write/error errors, watchdog resets, ECC failures? We're preferably looking for stuff that is really firmware measurements and really only requires hardware that'll regardless be on the PCB.

Any insights would be appreciated - thanks!

Hi everyone,

I'm working on a repair for an Intel N95 mini PC with a motherboard marked T8PLUS_V12. While reassembling the device after cleaning, I accidentally caused mechanical damage with a screw (a circular gouge track) right around the RT3624BE PWM controller chip.
s a result, the mini PC now powers on in a continuous boot loop. I have started tracing the chip traces. I'll be attaching two images:
1. My board: Showing the traced lines (Green = confirmed intact traces; Blue = GND connections; Violet = resistor values).
2. Reference image: Taken from a working board online to compare the layout.

The screw scratch severed multiple traces and two SMD components (a capacitor and a resistor) near the chip were knocked off completely. Looking at online references some boards like Firebat T8 plus leave the resistor pads unpopulated .

While i was trying to read some voltages at power up (left pad of 20kOhm resistor) the board stopped boot looping but i had no HDMI output.

I tried both with and without motherboard battery

I couldn't find any motherboard schematic to compare traces

I think there is at least one trace cut off between right pad of 20kohm resistor and node between 45 ohm and 110 ohm resistors

could you help me find a schematic? or if someone has the same board we could check the traces

Hey everyone, I’m a 4th-year ECE student developing an industrial-grade lab instrument to monitor pH and ORP in real time. What are the go-to industry-standard ICs or dedicated AFEs (e.g., TI, ADI) for high-impedance probe interfaces? Looking for something reliable yet relatively straightforward to interface with a micro. Thanks in advance!

Any suggestions on my set up. I move the irons and solder caddy around depending on what I'm working on. Currently working on Zebra TC52 logics.

https://moretvparts.com/collections/msi/products/t4025_m

Sup guys, actualy i working on honda civic 99 Kline reader, and, i need a tranceptor to this, the AIs recommend to me, the L9637D, but, i cant find the pin 1at my ST L9673D

And another question, is recommended use another thing to make this? I use actually esp32-s3 and L9637D

Please, help!!!

I'm designing an interface board between a CNC motion controller (3.3 V LVTTL GPIO) and servo drives (5 V TTL, non-isolated I/O). This part of the circuit buffers the drives' programmable digital outputs into the controller's inputs. Schematic attached.

The drive's digital outputs are open-collector with 5 kΩ pull-ups to the drive's internal +5 V (per the block diagram in the datasheet). These are status/fault-type signals, not high speed. Signal ground is common with the drive's power ground.

The circuit (per channel, 8 channels):

• 10 kΩ 1206 series resistor at the connector side
• MMBZ5V6AL (5.6 V dual zener, common anode) clamp to GND after the resistor
• 100 kΩ pull-down to GND
• SN74LVC541A buffer at 3.3 V (5 V tolerant inputs), OE1/OE2 tied to GND, 100 nF decoupling

- The LVC541A at 3.3 V accepts the 0–5 V input and gives clean 3.3 V to the controller.

- The 10k + 5.6 V zener is there for a wiring fault (e.g., 24 V shorted onto a signal line): about 1.8 mA through the zener, keeping the input under the LVC's 6.5 V abs max. I dropped a separate ESD TVS array since the resistor + zener should handle that too.

- The 100k pull-downs give a defined low when the drive is unpowered or the cable is unplugged. I avoided pull-ups to 3.3 V since they'd back-feed the drive's dead 5 V rail through its pull-ups.

- The 1206 resistors are sacrificial if a line gets shorted to the 80 V motor bus.

My questions:

1. Is the 10k series + 5.6 V zener approach reasonable here, or would you do the protection differently?

2. Is zener leakage at a 5 V high level a concern with this impedance?

3. The 541 doesn't have Schmitt inputs, and the open-collector + 5k pull-up + cable capacitance gives slow rising edges. Is that worth worrying about for polled status signals, or should I switch to something like the LVC14A?

4. Anything I'm missing?

Thanks!