Photograph via snooOG

A subreddit for practical questions about component-level electronic circuits: design, repair, component buying, test gear and tools.

A subreddit for practical questions about component-level electronic circuits: design, repair, component buying, test gear and tools.

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Doubt change values capacitor smd ceramic

Is the ceramic smd capacitor very sensitive to humidity? What humidity changes its values?

During long term storage when changing values ​​of the ceramic smd capacitor does it immediately die?

I have many devices that use SMD ceramic capacitors portable consoles, consoles, TVs, video games all stored

19:23 UTC


Flyback transformers without any load


I’m currently considering building a diy electric mosquito killer. The idea is similar to those racket in which one grid is connected to high voltage and another grid is the negative side of the circuit, when a mosquito get in between it creates an arc, killing the mosquito.

I’m considering using an aliexpress voltage step-up, that are as far as I understood flyback transformer.

My question is, are these voltage step-up supposed to be used with an opened circuit on the output (waiting for a mosquito to close the circuit) or will it create any problems ?

Thank you

1 Comment
19:10 UTC


Strengthening the internal antennas of my karaoke machine

I have a karaoke machine that has relatively poor reception to both of its wireless microphones (I can't get more than 6 feet away before it intermittently disconnects or stops receiving audio). I've opened the unit up and believe that these are the two little antennas for the microphones.

Are these just a shielded single wires (copper or other metal)? Can I replace it with wires to run outside the box for better reception, or connect it to hard antennas from an old router? I seem to have a lot of room inside this unit to add anything that might help it.




1 Comment
18:43 UTC


Trying to see what's wrong with my broken amplifier, the circuit board is face down (?) but I think this capacitor may be broken.

18:00 UTC


SMPS instability in CRT monitor

I have a CRT monitor (Sony CPD-200ES) that I am trying to repair. I think I have narrowed down the issue to the SMPS. I'm asking here besides the CRT specific subs, because it seems to me that here are more folks with expertise in the workings of switched mode power supplies.

The problem I'm having is that when the current draw drops (when the screen goes from white to black) all the output voltages of the SMPS start oscillating for a second or so, causing the picture to shake. After stabilizing, the geometry is off in high contrast scenes, which means that the supplied voltage does not match the calibration of the geometry correction circuitry.

I have checked C650,C651,C652 and C620 with my ESR meter, confirmed that D614 works correctly, that R659, R660 and R661 are in spec, that R609 is in spec and D604 is good. When I measure the outputs of the power supply with my scope, it becomes clear that the duty cycle of the SMPS oscillates, making it clear why this oscillation appears on all of the voltage rails of the monitor. Would anyone have an idea what could cause this and what I could check next?

schematic of the power supply section

Below are scope some of my scope measurements (100x probe). The test was displaying moodlight.com in strobe mode to cause the problem behavior.

SMPS secondary output (left: white screen, right: black screen before stabilizing)

AC mode at C650, L: black after stabilizing, R: white (sorry for swapping sides..)

18:15 UTC


My $1600 special-order LG Monitor has died, apparently due to a (now) well-documented heat issue leading to a ribbon cable melting. I'm fairly skilled at soldering work, but don't know where to get a replacement ribbon cable.

Hello everyone.,

I am heartbroken over the sudden death of my LG 34GK950F Monitor. I've had it for only about 5 years, and yesterday, it suddenly started to make a buzzing noise, as thin white horizontal scanlines appeared across the screen, before the image faded away to black.

I bought the screen shortly after it came out, but now that some years have gone by, it seems to be a pretty well-documented failure mode, as can be seen in the linked page above. It seems a thermal issue is leading to ribbon cables melting.

I have spoken with repair shops and they've said the monitor is too old to have replacement parts available from LG, so I'm going to try and repair it myself. I'm fairly experienced with electronics and soldering work, though I've never tackled something with as many connectors as a ribbon cable.

My question isn't about how to do the repair, but rather, how does one spec out and purchase a replacement ribbon cable? I don't even know what type of connector I'm looking at, or how the nomenclature works for ribbon cables.

Any help is appreciated. If I can't find a replacement ribbon cable, my next approach will be to buy a broken monitor on Ebay and do a Motherboard + cable swap, or just use the cable from that screen.

I will also find a way to increase the cooling through the chassis so this problem doesn't happen again.

Thank you.

18:10 UTC


Please explain rotary encoder with "right angle tactile"

I'm starting work on a project to design and build my own input device for CAD software and modelling, a project of a type and scale I've never experienced before. I need several sensors that are essentially just mouse scroll wheels (the type that act as a button too). Apparently most mice just use a rotary encoder with a switch underneath one end of the axle since all the rotary encoders with built-in switches seem to be parallel to the axis of rotation. Anyways, I was planning on just doing that, but I came across this part which seems like it might have a built in switch at a 90 degree angle to the axis of rotation since its description is "Edge mount, right angle tactile, 160gf". If that is actually what it is, then I would be able to do the whole thing with just this one part instead of a separate encoder and switch. Unfortunately I'm completely new to sourcing parts, reading datasheets, etc. so I'm not actually sure if I'm right about it or how specifically it works. If anyone more experienced could help explain how that part works or knows of an equivalent one that would get the job done, I'd really appreciate the help on my first big project.

18:03 UTC


How can I fix solder this back

How can I fix or solder this back and what are these coil call?

18:01 UTC


Help requested - Create files for MiniDIN 6-pin breakout board


This may not be the right place for a request like this. If not, just advise me accordingly. I want to order some of these breakout boards for MiniDIN 6-pin for a project, but Sparkfun has discontinued the item. It's for connecting a PS/2 adapter. I know boards exist with the adapter already fitted, but I already have loose connectors. So I just need the bare boards.

Here's the link MiniDIN 6-Pin Connector Breakout and I've included pics below.

I reached out to SparkFun's forum and they suggested using KiCad to create the required files. Then send them off for creation. I know nothing about KiCad and it looks fairly daunting to undertake.

Can someone here do this or can you recommend a service? Happy to pay for the design work, but just not sure where to go next.

Thank you!

board front

board measurements

board rear

17:33 UTC


how to get more sensitive photoresistor.

hi im hella noob but im trying to build a circut to drop things from my dji mini 2. the drone has a small light at the front which can be turned on and off. im trying to use this to trigger the motor with an ldr but it isnt sensitive enough. btw it works fine with my phone torch. so i pretty much need to know what photoresistor to get cuz i have no clue what the numbers on them mean. the light is a small pretty weak led. also for ldrs is a lower number more sensitive cuz i cant find that answer anywhere all i can find is datasheets about waffle i have no clue. thankkksssss :3

14:30 UTC


LT1054 no output

Hi there,

I'm making a simple split +/-9V supply for a project using an LT1054 (TI-model).


This is the circuit I initially built that worked ok. I used tantalum caps as recommended. A problem I noticed was that the output could occasionally become unstable, oscillating between 0 and -V. My suspicion was that C1 was perhaps too small, so I replaced C1 with a 10µF tantalum cap. I tried the circuit again and now it's not working. The OSC-pin still has its sawtooth wave at around 19kHz (biased at ~1.4V, 1.2V Pk-pk)å, the REF pin is 2.5V, FB is at 850mV and the CAP+/- pins look like the pic below.


The symmetric waveforms are switching noise from my supply at around 65kHz. The negative waveforms I believe are from the IC at about 37kHz.

The output sits at a measly 150mV.

Switching for a fresh LT1054 exhibits the exact same behavior so I'm ruling out a faulty IC for now.

I feel like I'm missing some glaring issue or misunderstanding something?

Update: I *think* I found the issue? There may have been the slightest amount of solder jumping the pins CAP+ and FB/SHDN (I couldnt see it though, seemed clear to me). I just reheated the FB/SHDN pin and it seems to be stable now?

Update 2: When I switch it off and then on again it fails to start. By briefly touching the FB/SHDN pin it starts normally. If i leave enough time for the capacitors to discharge before switching on the power I need to bridge the FB/SHDN pin with the +V pin to power it on again. My guess is that the shutdown feature of the IC is the cuplrit then. I'm not exactly sure from reading the spec sheet how to keep the IC in a constant on-state when powered on?

15:34 UTC


Issues trying to read rotary dial on Arduino with debounce IC



I'm working on a personal project to turn a rotary phone into a message bank. User would lift the phone from hooks and an LED would turn on, dial a number, and play a message depending on the number dialed. Running on an Arduino Pro Micro (5V, 16Mhz), using an MC14490 Bounce Eliminator for the dial and hooks, and DFPlayerMini to play audio. The hooks and DFPlayer work as expected but I get no signal from the dial. Dial YEL and Dial WH are where the pulses come from. Any ideas on what the issue could be?

15:14 UTC


GE Washer/Dryer Combo. Washer portion not getting electricity.

Hey everyone!

Does anyone know how to identify the component of the motherboard that receives electricity?

Honestly, I’m not even sure if that’s the right question to ask.

I’ll post a picture of the motherboard, and if anyone could point out some potential solutions to my problem of the washer half of my combo not receiving power.

15:13 UTC


What this component? (Power steering unit)

I have a power steering unit that was retrofitted to a 1970's WV Westfalia. We've trouble shooted it to this component, but for the life of me can't work out what it the extact spec is. It has the numbers 3, 1, and 7 on it.

Can anyone identify what this is?

Thanks 😁

Sorry, images didn't load, they're in the comments.

13:51 UTC


Need to bodge-wire to a 6mil trace on a PCB... acetone to remove the soldermask?

I gotta bodge-wire to two traces on a PCB, the traces are 6mil wide, so about 0.15mm. I purchased some 0.1mm diameter magnet wire. Usually for this kind of job I use a Xacto knife to scrape away the soldermask over the trace but for 6mil it seems... risky...

My research lead me to https://prototypepcbassembly.com/how-to-remove-soldermask-from-printed-circuit-boards/ which said acetone can be used.

Has anybody actually used this technique on a fully populated PCB? I can do it, and safely too.

Or is the knife still feasible?

There's two QFN motor driver ICs on there and one SOT223 sized voltage regulator and then everything else is passives.

06:36 UTC


Adapting LM3414HV design: 56V power supply

I've been trying to find a cheap alternative power supply for the LM3414HV LED driver. I found a 56V adapter on AliExpress that might work, but I'm not totally sure if it's a good idea to deviate from the original design.

My LED light project:

  • 5 strings of LEDs
  • The white string has 16 Cree LEDs in series, so 16 x 3.2V Vf = 51.2V
  • Originally contemplated using a 52V power supply

My concerns:

  1. Using 56V instead of 52V
  2. Changing inductor and capacitor values to accommodate the new voltage
  3. Effects on LED current ripple and input voltage ripple


  • Original max LED current ripple: 500mA
  • Original max input voltage ripple: 200mV
  • Potential new LED current ripple: 225mA
  • Potential new input voltage ripple: 110mV


  1. Can I use this 56V power supply safely?
  2. Is it okay to change the inductor and capacitor values?
  3. Would the reduced current ripple (225mA) and voltage ripple (110mV) be a problem?

I'd really appreciate any insights or advice on whether this modification is advisable and what potential issues I might face.

Edit: Here's the link to the adapter I'm considering: https://a.aliexpress.com/_mrD8Oj2

06:10 UTC


Can anyone help me find this capacitor values

Can anyone help me find this capacitor values, It ripped from my atx motherboard

08:23 UTC


Attrition on SMT manufacturing

I’m fairly new in dealing with board fabrication topics and Need help figuring out attrition quantities requested by vendor.

We recently changed vendors due to LT, quality issues, and better pricing. We had already procured the quantities needed to complete boards with a 10% attrition. However, new vendor is requiring large quantities to account for lead + attrition; i.e. for 90 parts resistors needed, extra 150 for parts for lead + 5% attrition.

Distributor’s LT and stock is too long and too low to buy the quantities requested.

Dow you know why so many are required? What should I expect from vendor when discussing issue?

How can we overcome the problem? What can I propose?

Can leads be added? At what cost?

Thank you in advance for the advice.

08:33 UTC


Flush Cutters And Other Small Electronics Pliers (+ Tweezers) Advice

I hope this question fits this sub.

I'm in the market for some small pliers, but not completely sure which ones to get.

I'm leaning mostly towards the brands below as most seem to be pretty well respected, but I'm not completely sure which brand is considered the best at this time due to production changes that happen over time, so it's a bit hard to compare a review of one brand that was 10 years ago, and then another brand that was reviewed 2 days ago.
Also, I don't necessarily need every plier in the same brand. If one brand is better at side cutters, but another one is better at nose pliers, I'll happily buy separate brands, but if one brand is simply superior, I of course wouldn't mind having them all look the same.
But I would really appreciate some help with deciding on which brand(s) to get. Again, I'm not really looking for the best price for performance, but rather the best plier available.

So these are the brands I have been leaning towards in addition to my thoughts on each one. (Roughly arranged from cheapest to most expensive for me to get when buying >5pcs)

  • Schmitz / Ck / Bernstein I've seen these be recommended a lot as cheaper but still great quality pliers. The only issue I have with these is that I've seen some complaints regarding quality. Their not much cheaper than the other alternatives, so I don't want a worse quality plier to save 20-30% compared to Lindstrom
  • Knipex Most likely Schmitz pliers at a higher price with some of their own models, quality seems to be good, but for a little more I assume I would get a lot more quality and performance from the three brands below.
  • Tronex - I've heard a lot of great things about these, but I've also heard that they can be a little brittle and shatter easily. These are priced pretty similar to Lindstrom although a bit cheaper by 5-10%.
  • Lidnstrom Of course. From my researching, these seem to be the best of the best, but most of the people saying this also mentioned that they have had their pliers for 20+ years, meaning it's the older "made in Sweden" pliers. Now that Lindstrom has moved most of their production to Spain, the quality has decreased a bit, but I've noticed that they still make some pliers in Sweden, but not sure if these are the same quality today as the old ones. They also make some in France, are these better than the Spanish ones? And how do they compare to the Swedish ones?
  • Erem / Weller Erem also seem like solid pliers with really a good reputation. I've heard many say that they're better in both quality and performance compared to lindstom. They are a bit pricier, but I would be OK with that if their better. These are also about 20% more expensive than Lindstrom.

If there's any top quality brands that I'm missing, please remind / inform me!

I would also love some tweezer recommendations if anyone has any.
They will be used mostly for SMD soldering and other precision work. I've mostly been looking at Ideal-Tek (not their economy series as I'm not impressed with it) and Erem.
I don't know if there are many other competitors other than Vetus (and maybe Rhino?), but Ideal-Tek and Erem seem to be better.

12:26 UTC


MOV spot welder instantly destroyed 40A relay, help?

12:15 UTC


Troubleshooting Turntable Strobe board


Hey there, basically the title.

This board is responsible for the neon strobe light of the turntable. I am a total amateur just trying to DIY it. I only have an el cheapo multimeter and a soldering iron with me.

I have tested the resistors and they seem fine. I don't think my multimeter supports capacitance testing so no idea how to check the caps, no continuity and they don't seem any bulged so I guess they are prob fine. AC1 and AC2 come from a transformer and report 100V both, which from my understanding it's normal. However I can't see any output whatsoever in NE1 and NE2 which directly connect to the strobe light. (I think I should be seeing something between 60-100V, but no idea really).

Ideas on how/what could test next?

12:07 UTC


Is this just a NOR gate?

Is the thing labeled “AGUT” just a NOR gate like the one below it? Thanks

10:44 UTC


Forgive me for kicking a gift horse in the mouth but… (Soldering iron question)

What the HECK is up with the current market? Should I buy a Pinecil V2, or a Hakko FX-888dx, or a FNIRSI HS-02a (or B?!), or a T12 active tip clone station on Aliexpress, or an Alientek t65, OR A SQUIRE SI012?!?!

I am so confused and at a loss. I currently have a RadioShack 64-053 (rebranded Atten AT-201d) digital 60 watt station and a Weller WLC100, however the shack iron, I keep cracking heating elements when I swap tips and it’s tough to find a suitable replacement.

So I start looking around online. I cannot justify purchasing the Hakko right now and to be honest I am hesitant to. The features an active tip offers make a LOT of sense to me considering I’ve just had to order my third replacement iron in two years to keep my RadioShack model running, and the Hakko uses the same base concept.

Are these active tip irons really as good as they say? I build guitar pedals and hope to do amps. (I would love to just use my weller which has been way more reliable but it has absolutely no finesse, so it has a tendency to overheat components) Could one of these active tip USB-C/DC Barrel jack irons cut it for me?

If I can get a year out of a Pinecil V2 or FNIRSI HS-02a/b soldering four hours a day I will buy it immediately, but I need some direction here from someone who has used a bunch of these.

Are they legit? Do they deliver what they claim? Are you happy with yours?

Signed, an annoyed 907/936 iron user. (This is a genuine question. I am looking for folks who have used both)

10:13 UTC


Beaglebone based LCD driver does not seem to initialize the LCD screen

Hi guys.
I am using a beaglebone black, running the default OS on it. I have written a driver to create a device for the LCD JHD162a( clone of HD44780, though the data sheet might vary, which I have pasted below). The driver is written for 4 bit mode LCD operations.
I am powering the LCD's Vcc, ground, backlight and contrast with a 5V power supply(9v through 5v voltage regulator 7805). I see black blocks on the LCD, when I set the contrast.
Now when I bring up my driver(insmod). I dont get anything on the screen when I try to write to the /dev/lcd file that got created when the lcd was brought up.

I have a doubt that the init sequence that I am using might not be correct. Could you please help me out by taking a look at the code and datasheet that I have pasted below. Any guidance would be much appreciated :)

Code: https://pastebin.com/uE64Z6Qw

Datasheet for JHD162a : https://www.rhydolabz.com/documents/display/JHD162A.pdf

09:48 UTC

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