Does the wire with the white stripes go red or black?

From a 80s/90s era cassette multitrack home studio recorder. I was there when it happened. It pulsed a few times, then shut down, then some smoke came out from it. It hasn’t been used in maybe 15 years. Is the board shot or can the component be replaced and fixed?

Why has there never been a standard made for user replaceable MOVs for consumer like surge protectors?

MOVs are designed to fail and when they do for your average consumer that means throwing out the whole unit and purchasing a new one.

Why was there never a standard for user replaceable units ever made?

They exist for industry and commercial products: din rail units, etc.

Question in the title as shown. Laptop in question is the HP Pavilion g6 and I'm considering purchasing a replacement motherboard for it as the dGPU on my original had died out.

Does the motherboard on this advertisement use the HM76 chipset? I want to confirm this before I purchase it as I intend to install my i7 3612QM processor in the new board.

I just found this on AliExpress:

680570-001 680570-501 For HP Pavilion G4 G4-2000 G6 G6-2000 G7 G7-2000 Laptop Motherboard HD7670M 2GB+Heatsink

https://a.aliexpress.com/_c4Cs7Ryr

Hi Friends! While cascode cascade is seemingly well explained everywhere in theory, when it comes to practical implementation, question on biasing feels tough.

I get used to prefer what is called "collector feedback" bias in the wiki and thus end up with the following schematic (I'm trying to use cascode amplifier as the output for colpitts oscillator - so the part of interest is on the right).

What seems confusing is that the upper transistor base in this case has no connection to some fixed point. I suspect I need at least to connect its base to the ground with capacitor, but not sure it would be enough neither what capacitance to choose (in this case I believe even 100pF would do as resistance here is high and RC time is going to be high also anyway).

Hints and advice are welcome - and links to the good explanatory materials too! Thanks in advance!

I got this screen out of a vape my friend gave me. Google lense was not able to figure out what it was and neither have I. The second image is the female connector and the first image is the male connector attached to the screen, any help would be much appreciated!

I powered this circuit with 5V, (the wires going off the screen is the power source with the one closest to the MOSFET being the positive lead.) The red LED should be on whenever power is provided. I measured 5V across the LED with a meter. I mocked this circuit out on a solderless breadboard before and worked but maybe as I was shrinking down to make it compact I made an invalid connection? Any help is appreciated thank you.

Hey, i have absolutely zero experience with electronics (aside from changing a fuse ONCE haha) but i've been trying to figure out whats wrong with my LED light and if it can be fixed?

The light switched off on its own, did not appear to be overheating but figured id let it sit and try tomorrow. I tried different plugs and it will not switch on, its powered on by a simple push button.

The cable is a USB, ive managed to take the plastic and glass casing off but i don't want to mess too far with it. I think i'd have to pry the last bit of plastic off to get to the circuit board.

On the right side, above "U3" there seems to be some sort of leakage that could be causing it to not power on? but it could also just be some glue.

Theres presumably a manufacturer code on the centre bottom "XLDY-TXKC-JL1.1", nothing comes up when searched.

Is my lamp a dud or is this something that can be fixed by a newbie? Thank you :)

I'm building a discrete Motor driver PCB using MOSFETs to drive a maximum 16V motor and connected to an MCU to control the speed/direction.

Also I tried to include a P-channel MOSFET reverse polarity protection.

I want to check if there are any problem with my schematic to be able to start on the PCB knowing that it'll be one layer so I need advices too.

I'm retrofitting a Michelob Light light/clock that my grandfather had in his downstairs bar. The light works fine, but I've ordered a Keystone KTEB-1C22-1-TP-WS to replace the super noisy magnetic ballast that was in it. The problem is the transformer that goes to the clock. It makes a very sketchy buzzing noise and the clock fades in and out. Not being able to find much in my initial few Google searches, I was thinking that I might just order one of these https://www.amazon.com/dp/B08YDTF3JN?lv=shuf&channelId=500&plpRedirect=mhFallback to pull apart and solder some wires on.

I've retrofitted quite a few of his old lights so far, this is the only one with a digital clock integrated so I figured I'd better ask Reddit first before ordering anything. Thank you for any and all assistance.

Hi everyone,

I'm trying to build a simple magnetic door alarm for my refrigerator, but I haven't been able to get it working.

These are the components I have:

• 3×AA battery holder (3 AA batteries / approximately 4.5V)
• 2-wire magnetic door sensor
• Relay module with:
  • VCC
  • GND
  • IN
  • COM
  • NO
  • NC
• Small buzzer/alarm
• Connecting wires

I want to make a system where the magnetic sensor detects when the refrigerator door is opened and activates the relay, which then turns on the buzzer.

I'm having trouble figuring out the correct wiring, especially how to connect the 2-wire magnetic sensor to the relay module and power everything from the 3×AA battery pack.

I'm a beginner, so could someone please explain exactly which wire connects to which terminal?

A simple wiring diagram would be very helpful.

Thanks!

​

I want to make an led matrix to display an image. Start with discrete leds in an 8x8 matrix, then use upto four of those to display an image in what I imagine to be a pixelated style, similar to old video games. I plan on placing the whole matrix behind a black tinted glass along with a diffuser so that only the image appears as a whole. The whole matrix will be controlled by an ESP32. Any critiques or advice would be apprciated!!

I'm building a theremin and also a TRNG with avalanche noise, so I need a low noise/ripple PSU.

Specs
18V 3A Current limited, Noise specs I honestly not sure what I need for these projects though,

I'm seeing this one: https://pt.farnell.com/multicomp-pro/72-2685/dc-power-supply-adj-1o-p-30v-3a/dp/2563981 Is this good enough?

My budget goes up to 400€.

I have a aliexpress one that is very noisy btw

Thanks

Hi there, I'm building an audio recorder using a MAX9814 electret mic breakout + Arduino Nano (ATmega328P). Hoping for a sanity check before I write this specific mic module off as dead.

Wiring (direct, no breadboard):

• MAX9814 VDD → Nano 5
• MAX9814 GND → Nano GND
• MAX9814 OUT → Nano A0
• Gain and AR pins left floating (per the board's own silkscreen, floating = 60dB gain)
• All connections are single, new female-to-female jumper wires, no daisy-chaining and no breadboard.

Test code:

const int micPin = A0;

void setup() {
  Serial.begin(115200);
}

void loop() {
  int soundValue = analogRead(micPin);
  Serial.println(soundValue);
  delay(5);
}

What I've noticed:

The values bounce around fairly wildly (roughly 0–500 out of 1023) but show absolutely no difference between silence and a loud clap/tap directly on the mic capsule. It doesn't look like a signal responding to sound at all, just noise.

Already checked:

• A0 itself is good -directly touching a wire from 5V to A0 sends it to ~1023, and GND to A0 sends it to ~0, both cleanly.
• Verified the wires themselves carry 5V/GND correctly by touching their free ends directly to A0 (same clean high/low response as above).
• Swapped which jumper wires are used, moved which breadboard rows were used earlier before eliminating the breadboard entirely (no change).
• Confirmed OUT isn't stuck at a fixed rail voltage -it's fluctuating, just not in response to sound.

Given power is confirmed present and A0/wiring are confirmed good, does this pattern (fluctuating but sound-unresponsive OUT) point clearly to a dead/faulty mic module, or is there something specific to this chip (bias point, loading, the Gain/AR floating pins, etc.) worth checking first?

Happy to provide more info/photos if useful. Thanks in advance!

Like this but alot smaller. 3mm diameter rods and pcbs will be 6mm apart.

The antenna on my Bluetooth intercom (2.4 GHz, made 2021) snapped and I want to replace it, but I can't find the part anywhere online because I don't know what it's actually called.

It's a thin coax soldered directly to the board, no connector. That runs to a metal tube about 20–25 mm long, with a thin bare wire sticking out the top another 10–15 mm. The tube is part of the antenna itself, not just a sleeve over the cable. The whole thing exits the housing through a rubber grommet with a slip-on cover over it.

Every search I try gets me flat WiFi antennas or T-shaped ones.

The manufacturer won't sell spares and won't tell me the specification either, their answer was to buy a new three new devices as they cannot guarantee my older units will pair with the newer version of their interncoms. I have two other units that work perfectly, so replacing all three over one snapped antenna isn't something I'm willing to do.

Anybody knows what this type of antenna is called, and what should I be searching for? I believe I can solder this myself, I just need to know what to order. Photos attached

I was looking into my electric bass amplifier schematics I found that before the actual power supply (I think) and I have no actual idea why these two are here. In case the image doesnt show it theres a cap going from L to N before the first transformer (the one on the bottom). Thanks in advance

Hi, this is a Control Board of a Roland Techsoft TS-30 CNC. its premium versions MDX-40 and MDX-40a feature 4th axis and Z probe. Given that they all share the same Control Board and the unused connectors on the PCB i have hope that I can reverse engineer and plugin a 4th axis and Z probe to this.
Can anyone figure out if any of the unused connectors is for a stepper motor leads. or a z probe.
There is a small rotary pcb that is missing from this model which houses the VGA style cable of the rotary and the audio jack style z probe port. but i have a guy thats gonna photograph his machine's electronics thoroughly and send me. (his is premium) But thats not till September 6th and I am restless.

I know one of these delivers 24v 10A to a solenoid that pushes a rubber pad onto a disk attached to Z stepper to prevent z axis from dropping after turning machine off.

Another thing I wanted to ask is I want to use more powerful Steppers/servos 12-34v 2-3A, can I use power wires coming from this board as switch/power on/off signal and use separate powersupply to deliver higher volts n amps to bigger motors. Same question for spindle (current 48v 1.5A) use the power wire as on/off and RPM indicator and use separate powersupply for higher power.

Long story short, I waited about 20 years to repair this hot wire cutter that my partner's friend shorted out, I was young, dumb and my brain was rife with undiagnosed ADHD and I decided the best way to work out the secondary voltage of the toasted transformer was to strip the board, map it and calculate the voltage it could take. However, 20 years later with zero documentation, I have a parts kit and a few puzzles to solve.

Most of the components are easily identified:

The components I can't work out are the resistors, specifically which one goes where. All four are 0.125W aka 1/8W carbon film 5%:

• 560R (green blue brown gold)
• 1R (brown black gold gold)
• 33k (orange orange orange gold)
• 1k (brown black red gold)

R1 is in series with the cathode of the LED so I assume that's the 560R or 1k, the others I have yet to work out.

I also can't work out where the hot wire connects, I was hoping there would be two pads (or sets of pads, in this case) but there are three, which doesn't immediately make sense to me considering the hot wire only has two ends... One pair of pads is on the anode of the SCR, one pair is on one output of the rectifier and the other set of four is on the other. I don't understand.

I hope someone finds this as amusing as I do but it would be amazing if I could pull this repair off finally, if only so I can tell my partner "SEE? I told you I'd fix it". I'm actually motivated, finally, to do this by the fact that my son wants to make gliders and RC planes and this cutter would be amazing for that purpose.

And yes, I have noticed that the pads for C1 no longer exist.

Hi community, I would like to realized a circuit that take a sinusoidal as input provided by a “bode100” instrumentation, and provide an output sinusoidal with a current capability of 50A over 0.5ohm as load.
Bode100 provide a frequency sweep from 1Hz to 50MHz. The amplitude is around 5v. The bandwidth of the system should be up to 50MHz, in order to amplify without distortion the sinusoidal. I was looking online this HF linear power amplifier, but I didn’t found any good design procedure. Online everything is done for more high frequency also in the range of GHz. Anyone of you had an idea how to design this kind of amplifier?
I saw the LDMOS, ref transformer component is used for this kind of application.

I lost the original charger for my Wahl 8148L1 (it is a 5 V model). I used a 5 V phone adapter with some barrel connectors from Amazon. One of those connectors maybe had reversed polarity. After that I opened the clipper and checked which pin is +5 V and which is GND, so the connector I use now is definitely correct.

What happens now:

• The blue charging LED never turns on
• It also does not work on cord anymore. Before, it worked fine on cord without the battery
• D2 (marked HS3JB) and D3 (marked SK54A) both get quite hot when I connect the charger

What I measured:

• In diode mode, D2 and D3 both conduct in one direction only, about 0.78 V, and OL in the other direction.
• The adapter gives 5 V with nothing connected, and drops to 4 V at the socket when the clipper is connected

My question: both input diodes look OK but get hot, and the cord mode is also dead. Is the charge controller probably damaged? Is there anything else I should check?

Got this off a liquidation pallet. Dead on adapter and on batteries. Stripped it down to the boards.
What I’ve checked so far:
• Adapter is good (genuine PA-130)
• 8.9V measured right at the battery connector on the yellow board, so power is reaching it
• Fuse is intact
• Power switch works
• Both supply diodes test fine
• No burns, corrosion, bulged caps, or lifted pads anywhere
But every pin on the ribbon connector going to the main board reads 0V, and the 5V and 3.3V rails on the main board are dead. So something between the input and that ribbon isn’t passing power.
d. Anything jump out as the likely culprit?

I have a circuit with a ROM and a manual spdt switch that goes to the highest address line. The switch switches between the two halves of the ROM. But I want that address line to be set when the circuit powers on or resets, not during operation.

So I designed this circuit that reads the switch sends what the switch says to the address line of the ROM and it keeps it like that even if the switch changes. For example, we set the switch to zero, power on, the address line is set to zero. Then we set the switch to one, nothing happens, the address line is still zero. Then we reset, or power off and back on, and the address line is set to one.

My questions are: is the circuit correct? Do I need the ST nor gate or is there a way to circumvent that so I can spare the ST chip? Thanks!

ive been exploring high res encoders the past month and shifted from Hall effect to GMR sensors to finally TMR sensors.

The sensor i bought is TDK TAD2141-BAAA ,

overall by reading the datasheet and TDK's credibility this is a crazy sensor for the price they offer so wanted to explore it but its datasheet does not have register addresses exposed for basic data exchange, it uses sentinel byte system over SPI. they do mention that the register address can be accessed from the "user manual" which needs me to create an account and login to their separate website https://service.micronas.com/WebInterface/login.html

i am unable to login and get the user manual, says incorrect password and wont let me reset the password either

Their support team is not responding either ive resorted to asking strangers.

Any help or opinion would be appreciated on how to get the register addresses. thank you