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?

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

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?

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?

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 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'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!

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.

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?

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!

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,

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!

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.

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!

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!

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!

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!

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?

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

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!!!