I am trying to get a grasp of how to identify what power standards various PSUs claim to conform to. The label on this Dell PSU is ram-packed with info, but I see no direct claim that it supports USB-PD at all.

The range of voltages might imply that perhaps maybe it’s USB-PD, but I see no indication where they take credit for that; much less a particular PD revision. IIUC, that means if it’s USB-PD non-compliant and someone drags Dell into court, they can say to the judge “we never said it was USB PD-compliant”.

The review that probes this thing shows that the PSU is detected as PD3.0. Yet at the same time it does not support PPS according to the blogger. So wtf.. how can it be PD3 if it does not support PPS?

It seems Dell is banking on consumers not being keen to read the label. According to the blogger:

The odd thing is that it is advertising itself as a 96W adapter (20V/4.8A) which is different to the printed 20V/5A rating on the rear.

So it seems has Dell decided that if they do not benefit from advertising a capability, they might as well not mention it and downplay what it can do, for legal purposes.

The blogger goes on to test it with all kinds of fancy costly gear that no typical consumer would have. When I am at a street market rifling through a pile of dumped electronics, how do I know what I am looking at? Do any of the cryptic symbols on that Dell label suggest USB-PD?

cross-posted from: https://infosec.pub/post/51092505

I have a 3-pin Dell PSU spec’d as 19.5v 3.34A and DMM measures at 20v unloaded. The power reqs on the HP laptop are 19.5v 3.33A. AFAICT, that’s a match. Even the 3-pin barrel connector geometry matches. So what’s the problem?

The center pin is a “smart pin” aka “data pin”, as I came to learn. According to @over_clox@lemmy.world, this PIN basically passes brand info so HP can reject non-HP PSUs. But according to this article, the data pin is used to “regulate” the voltage -- which I take to mean it negotiates the voltage for transmission as USB-PD does. If it’s merely negotiating power reqs, then the Dell should work.

It’s possible both sources are correct.. perhaps HP has its own proprietary way of negotiating voltage and Dell has theirs.

Someone even claims that the data channel is used to communicate temp info so a PSU does not overheat. If that’s true, then perhaps it was a good design (noting that the USB-PD standard did not emerge yet).

But is it true about the communication? Considering there are hacks with a resistor or something to satisfy the data channel, it’s hard to believe that the communication is that sophisticated.

This page advises HP owners to always buy HP-branded PSUs. But it’s unclear if that’s just overly safe nonsense.

The 240-120 voltage problem can be remedied by using transformers but that doesn't negate the frequency difference between grids. Australia operates on 230v @ 50Hz while the US works with 120V @ 60Hz for instance, as certain electronics that are singular voltage (Hair Dryers, Desk Fans or Electric Blankets) have their frequencies disclosed even if the voltage on those are different than the one that country uses.

Does plugging in a device that has 120v-60Hz via a transformer on a grid that operates on 230v-50Hz ruin the device due to either heating elements or motors inside? Even between countries that work with 220-40v but one uses 50Hz while the other uses 60Hz, does that render those electronics (like dehumidifiers, power drills, curling irons) incompatible despite them using similar voltage (like 220v vs 230v)?

I have a problem with the receiver for my 5.1 system.

When I turn it on, the speakers start making a popping sound that continues for a few minutes. I have tried disconnecting the speakers and using different ones, as well as different inputs, but the issue remains the same. The popping lasts for a shorter time if the receiver has been turned off for a while. Initially, it only lasted a few seconds, but it has gradually got worse.

Watch the video to hear the sound. In the video, I have only connected one speaker.

The receiver is a Marantz NR1501. I'm not sure when I bought it, but I found a review from 2010.

I opened the receiver and inspected it, but I can't see anything burnt, and all the capacitors look OK.

Do you have any idea what the issue is? How can I confirm if that is the root cause?

So, I'm tinkering with the ATtiny 3224 and its PWM capabilities. I can get 256 bits of resolution per cycle at 78.125kHz.

If I drop to 32 bits, that gets me to 625kHz, as shown in the screenshot.

I've done some searching but I may not know the right term and I'm probably looking for a rule of thumb.

What sort of resolution do you need to regulate a DC/DC switch mode? (in this case a pure resistive load that doesn't change)

I think it might be something like a factor for required percentage of change of switch ON time. Such as, you should generally be able to modify your duty cycle by increments of 5% or 0.5% or whatever for proper regulation.

Does this factor have a name?

So I'm kind of new to electronics but I understand a fair bit. The power button he solders in connects the board directly to the ground through the grounding pad and one of pins for the port to the button. This bypasses the capacitive touch sensor on the 360 slim and allows you to turn the console on with a physical button.

How exactly is that happening?

How does capacitive touch work?

Isn't this the same as connecting the board->ground and pin->button->ground? As I understand, electricity takes the path of least resistance so both lines will flow to the ground, or is it different in circuitry than houses?

If so, could I wire to use a 2 pin mechanical keyboard button for the power button to connect the pin to the ground and just bar fuse the board and ground?

The touch pads have very easy to follow traces that connect 5:5 to the port I understand that capacitive touch is different somehow, but couldn't you just solder a button to the contacts on the port?

Any help would be appreciated, I'm working on a total overhaul of my old 360 slim and this is going to be a big part of the aesthetics when I'm done. I'd very much like to get a good tactile button for the power and eject.

Which do you prefer? I have the option to do both but milling seems to take awfully long and produces a lot of noise and glass fiber dust. It has the benefit of not needing etch resist which is also messy.

Chemical etching with iron chloride is also quite messy. First applying etch resist, removing part of it, etching etc. It is much simpler though and you don't need a CNC machine for this.

My friend told me that macbooks have their RAMs behind the CPU (or something along those lines) and it got me wondering. Does the distance between CPU and memory really make that much difference? 🤔

I am working identifying a problem in a VFD for a friend's belt grinder, and I've ID'd the other ICs on but, but I wasn't able to ID this last 8-pin one. I know it's made by Microchip, but couldn't pull anything up from the codes on the front.

It's possible this is an encryption key chip with some obfuscated info on the front. However, I don't know how common that actually is.

Any help is appreciated.

UPDATE: Looks like this one's solved. I went back and double-checked the code, and it looks like y'all were correct on it being '4A08I' and not '4A081'. This chip is also the closest IC to the MCU which lines up perfectly with this being an EEPROM.

I appreciate everyone's input and help with this!

I'm tinkering with the ATtiny 2 series (ATtiny 3224). I'm also starting to teach myself about switch mode power and surface mount design. I'm planning to drive two Toshiba SSM6K804R MOSFETs. They are logic level MOSFETs with a 4.5V drive. They have a gate capacitance of 1110pF (1nF).

Even though these are logic level MOSFETs, I think I still need an external gate drive for them for crisp switching above a few kHz. I don't need to try and charge the gate directly with the ATtiny as I would need a 2-300ohm resistor in series to protect the microcontroller and that will slow everything down. Also need a pulldown for the gate.

Can someone please recommend a simple IC or maybe a packaged transistor pair that I can slam the gates with?

Questions/comments/advice greatly appreciated!!

I'm currently repairing a device and I'm trying to understand what this circuit board does and how, and whether it is causing the malfunction. While doing that I stumbled upon this resistor whose color code does not agree with my multimeter. I'm measuring 152.1Ω, but the way I'm reading the colors it should be the very common value of 69.1MΩ. If I reverse the order, I get 1.51Ω/15.1GΩ/151GΩ, depending on whether the second color from the left is silver, grey or white. Black would give me 151Ω, but it definitely is not black.

The device this circuit board is from is pretty old. I don't know how old, but there is exactly one IC on it, with a datasheet published in April 1974. The relay in the background has 1979 written on it; I'm not sure if that is supposed to be a year.

Any ideas? Am I reading the colors wrong? Do I trust the multimeter or the markings regarding the intended value of this resistor? Have you seen resistors whose color codes have changed over decades of use?

This cute little monster has chewed a single earbud from not 1, not 2, but 4 🫣 pairs of Shokz Openfit 2+ earbuds. I really don't want to buy a 5th pair.

So, I have 4 unchewed earbuds, evenly split between left and right, but none of them connect to each other. They each also connect to a different charging case.

Question 1: Does anyone have a clue how these things connect to one another? Is there any chance that I could pair them without having to open them up?

Question 2: If 1 isn't possible, is anyone willing to get on a video call with me and see whether you can guide me through switching out parts to repair one of the chewed earbuds? I have no experience with this kind of thing. I have some ifixit tools from opening up an iMac once, and even a (never used) solder. Whether these will suffice ¯\(ツ)/¯

I'm repairing an old TV with corrosion on the board. I'm having trouble reading the schematic from the manual. Here's the relevant section: I have two questions:

Do the thick bars on one side of the capacitor and the base of the transistor indicate those are connected together? I'd tone it out but the board is heavily corroded and I'm unsure if they should be connected. I've also seen these bars on other parts of the board, but the components there are not rated anywhere near as high as C451. I feel like that risks high voltage backfeeding through the other parts of the circuit.

What kind of capacitor is C451, and should it be polarised? The BOM lists it as a pp cap which I understand to be non-polarised, but I can't find any key that tells me what the dot on the symbol means. Let me know if I can provide any further information. Thanks

From the service manual for the Yamaha DX-100 FM synthesiser. The way this looks to me, both the 12v DC power supply, and 9v DC battery power get routed through exactly the same voltage regulator.

So it should be possible to just straight replace the 6x C-cells with 3x 18650s without needing to make any other changes, right?

I know exactly enough electronics to be dangerous, which is why I'm double checking here in case I've failed to account for something.

I'm aware that fresh 18650s put out a little over 4v, but I seriously doubt the vReg tops out at exactly 12v. I can disassemble the unit and check part numbers etc if necessary but I was really hoping to avoid that as it's quite a chore.

Hi Sparkies

I have hit a fibre network conduit in the garden but luckily the fibre isn't damaged. There is an old, redundant copper landline cable in there that I damaged.

My question is, can I patch the PVC pipe and walk away leaving some residual moisture trapped Inside? Or will the whole section need replacing and sealed up?

I have opened a support ticket with the provider and awaiting the official report on repairs.

I replaced my fridge ice maker a few years ago because part of the circuitry burned out. The replacement has also now burned out (though not nearly as badly). For reference, the burned part is supposed to hold onto the end of a copper peg that leads to the heating element (which melts the ice slightly so it can be popped out of the mold).

It seems silly to spend $60 on a new one when it's just $0.05 worth of copper that needs replacing. Is there a safe way to fix this? Unfortunately, I can't just solder the connection because it is enclosed when assembled. For reference, those tabs aren't just fouled, they are burned completely through. My first thought is to pull out the whole trace, solder on new tabs (not sure where I'd get the material), and put the trace back in.

could i follow some soldering guide or is this beyond repair

I've got a vintage HP digital counter, model HP-5216A. It was working, right up until the moment that it fell and broke two of the tubes' glass envelopes.

I really don't know where to source Nixie tubes. I see a few people who are making clocks with them, but not selling individual parts.

It's apparently an HP-1970-0025, which is a rebranded Burroughs B-5560.

Don't imagine this is the right place to find them, but I'm hoping it's the right place to find someone to tell me the right place to find them.

I had an ECU for an air seeder blow up, so I'm rebuilding it from scratch using a Pi and other hardware. I got the shaft sensors reading fine, set up the relays and other switches and lights, but this one has stumped me. The markings give me nothing to go off of (Trison 91779847 Rev C gives me nothing useful), but I still have the borked board that I can trace out. The sensor is fed 12V and ground, and has a white wire that is marked for airspeed input on the wiring diagram of the ECU.

When I trace the white wire on this, it looks like it's conditioned by some diodes (two diodes, in opposite directions to ground) and a capacitor, with a pulldown resistor. The trace then goes to an opamp (TLC2272) inverted input via what looks like a voltage divider, and from there maybe feeds into the processor the board uses. Kind of hard to see from that point on.

I scoped it and if there's data there, it's in the 1-2mV range if I reference from ground, which makes the opamp make sense. But I don't have a very good scope where I am, I do have a Rigol at home that I could get.

I have built a very crude estimate of the airspeed just from the current draw of the hotwire using an ADC and shunt resistors, but I assume I can get a better reading from this sense wire if I can figure out how the hell it's working, via a reference circuit to help me understand. If you know this sensor or a similiar sensor that I can crib the circuit from, that would be awesome.

So I’ve been using an old repurposed tractor lamp as my bedside lamp. I wired it up to mains (EU 230V) with a well isolated alternative bulb and bulb holder (the original bulbs are impossible to find). This has all been grounded and done the best we could. Now comes the problem, we reused the original switch (as it looks good) which it turns out, does not really appreciate having to switch 230V instead of the 12V (or 24V?) it was designed for. I believe I can patch up the switch to work as designed, however I do want a better solution to switching the lamp on and off.

Do relays exist that provide their own low voltage power that I can hook up the switch to? There’s not a lot of space available in the lamp, so I was hoping for a compact, drop in solution.

Other ideas are welcome as wel. I’ve thought of converting everything to 12V, but that would mean finding a new bulb holder, and having a transformer to put somewhere.

I have to design a programmable frequency/clock divider circuit using the 4029 IC. Theoretically, the circuit should start to count down backwards from a given number and when it reaches 0, the 4029 should load the data from the ABCD pins.

The issue is that the countdown stops at 0 and PE doesn't get back to the LOW state. It loads the number, but the SR latch never changes its state so the IC can start counting again. I tried everything and nothing fixes the issue. What can be done in this case? Thanks 🍻

Hello everyone, We have a problem with a circuit we built. The circuit seems to work properly with a green laser diode (130mA, lower voltage). With the red laser (higher voltage) on the other hand, the circuit delivers only 60mA max of the 130mA it should be giving the laser.

The problem seems to be the transistor's resistance because it works properly if we bypass the transitor and give +5V to the LM317.

Is it this assumption correct?

We tried a few transistors (BC241, BC236, TIP41C and TIP41) but with no luck. Is there a way to find a drop-in replacement for the transistor? MOSFET seem to have lower resistance but require an external driver with Arduino.

We need to use the Arduino PWM with these drivers, so at least 980hz switching frequency is needed.

Thanks in advance

Link to the schematics

I'm wondering how practical it would be to drill and tap terminals to add posts to batteries like this: https://batteryhookup.com/products/2x-sunwoda-lf314-314ah-lfp-prismatic-cells-grade-a-qualified-rohs-certified-ultra-long-life-10-000-cycles

The description says that you can only drill 5mm at most. Anybody do something like this before? I do have a shitty Harbor Freight drill press and couple hand tap wrenches.

Recently acquired my first oscilloscope (Siglent SDS804x HD with license key "hack" applied) and I've been playing around viewing various waveforms with it. I have a simple microcrontroller circuit generating a 900Hz rectified sine wave, and it passes through a capacitor to remove DC bias.

I'm confused about what I'm looking at when I plug it into my scope. It seems like my audio signal is somehow being represented in the "negative space" of these traces. As I change my code (different freq, different wave, etc) the negative space changes to match. What I expected to see was something akin to this image: A series of square-ish pulses of different width.

What I would eventually like to figure a way to demodulate the audio wave and display it on my scope as its own trace, then play around by analyzing it independently of the PWM. I'm sure that somewhere in all the math functions on this scope, there's a way to achieve that, but I haven't found it yet.

So a while ago i got my hands on a old sewing machine sadly the foot pedal blew up on me and i also noticed that the machine made my fingers tingle (more on that in this old post here: https://sh.itjust.works/post/35395330 ).

After that i didnt touch the thing for a while but now i needed to sew something so i got myself a new motor and pedal for it online.

The motor fits neat to the machine and the pedal works. But after the last time i was a bit afraid to just touch it, decided to better do a voltage check first.

So i grabbed a Multi meter and connected one side to main earth, and the other side to the metal body of the machine.

And apparently there are 30-32V AC on the metal body of the machine :( Then i tested the current and it was 4.1uA.

I did the same thing for the motor spindle an and the results where even worse >.< 173V AC on the spindle and 43uA when i short it to main earth over the multi meter.

Now my question is:

Is this normal?

Is it maybe just some parasitic currents from the Motor windings acting as antenna and inducting voltage into the metal body of the machine?

Will it kill me if i touch it?

Should i ground the machine to earth using a second plug?

Should i isolate the motor from the metal machine body?

Here are some more pictures from my measurements and measurement setup: