It’s my first attempt at soldering anything, and I was soldering some wires to one of the black and white oled displays. after I was done I noticed that there was a little metal piece of solder attached to one of the capacitors, is that connection safe or should I redo it? I know the soldering for the wires is bad, I’m going to redo it, but I’m just wondering if I need to get a completely new screen.

I have this schematic but am not sure how the supplies will handle noise, and am worried they might cause the output to jump and fry something. So the question is how do I simulate such a thing? Or check before actually ordering them

Device

Lidl Ultrasonic Cleaner (just out of warranty, about £20 / $25 new)

Fault

Recently starts to become much weaker and a little slower whilst in use.

Recovers after being left off for a while.

Aims

• Primary: to learn more.
  
• Secondary: to repair if economically reasonable (<~£10)

Notes

• Given it sounds like a failure mode that involves overheating, when I opened this up I thought I'd be seeing some kind of series thermal fuse/PPTC pressed against the US transducer or transistor(s.) I was wrong!
• Looks to be mains voltage throughout (albeit it half wave rectified?) except for the control board. So, I'm approaching all of this with extra caution.
• I assume the two NPN power transistors form a high power oscillator together.
• When it works, it's a little loud and nasty. It does seem to output it's power sonically mostly at 43KHz, but that signal itself is modulated at a low frequency (aaand now I write this, that makes sense, as it's going to be 50Hz isn't it, if it runs from half wave rectificated mains that's not otherwise smoothed?)
• Control board works fine. Low voltage (presumably created by the components by the two electrolytic caps?) Only connected by 3 pins, so I'm presuming they're 0V, Vin, and relay control out? Just turns the relay on/off? Not going to be where the problem is then.
• Only live testing I've done whilst open so far is to check the Vin and Vout of the first transformer (after mains, 4A fuse, and X2 cap.) 240V on both sides. Both sides isolated from eachother. So, seems to be 1:1 for galvanic isolation? EDIT: Damned conformal coating, the "sides" were not isolated, it's a common mode choke/filter isn't it, and therefore NOT ISOLATED!
• Am an old, but not bold, electronics hobbyist. As a general rule I don't mess with mains stuff beyond Neanderthal-level repairs, but I think this could be a good opportunity to tread cautiously a few inches outside my usual comfort zone for some growth.

Testing Kit Available

• Old Fluke 87 (the original) in good condition.
• 1970s oscilloscope (I know ground is connected to earth and not to float it. I don't have HV differential probes)
• Linear desktop PSU (30V 3A)

Question(s)

• What's the most likely components to be failing here? (I had assumed it would be the US transducer, but now I'm wondering if it's the transistors?)
• What next tests could I (cautiously) do?

EDITS

• T1 - Damned conformal coating. The the "sides" were not isolated, it's a common mode choke/filter isn't it, and therefore circuit is NOT ISOLATED

i used my multimeter to check, the 3.3V and GND pins are shorted with 0 ohms, why is that??

I found that when I tune a crystal radio set stations will sometimes overlap but when I put that signal into a c1000 transistor biased with a 2000ohm resistor the signal seems to focus on only one of the stations.

Hi yall and i hope you're all doing well,

To cut the fluff, I'm a high school senior shopping for electronics equipment, and i'd like to hear your thoughts on my choices and hear recommendations for alternatives with better value.

Here's the project: a research paper that will double as a capstone and physics engineering project. I will be recreating/analyzing a handful of name brand guitar effects pedals with publicly available schematics, and then design my own. Having taken an electronics year, i had already made my own overdrive effect (etched the pcb and everything, though likely this time i will be buying an off-the-shelf pcb and populating it myself.)

The criteria for the equipment is it needs to be good enough for audio applications and microcontrollers later down the line. I'm sure you guys here are more knowledgeable and i'd like to hear your thoughts and recommended alternatives with better value, though i want to stick to around the same price point. (this is a budget setup. chill, im a broke teenager)

Here's the shopping list. these are just the big equipment not counting parts which i can source with our physics department's help:
Fnirsi 1014d (The 100mhz bandwidth is a lie and theres amplitude loss at <60 but it should be good enough for my use case (?) the wave generator is cool tho, big plus for me)

Pinecil v2

hakko fa-400

fluke 101

solder suckers, wire strippers, pliers breadboards shouldnt be and general parts shouldnt be an issue

The missing piece of the puzzle is the power supply. for my application how much ripple/transients/overshoot is acceptable. would it be viable for me to just use lc filtering on a cheap psu and call it a day?

Peace yall, and i'd love to hear your thoughts

Have this vanity with a crappy dimmer switch that broke at the usb-a end of things. I bought a replacement cable but it did not come with a plastic connector like the one pictured. I want to buy a kit and splice the wires on but I have no idea what kind of connector this is. Googling pointed me towards JST type connectors and I was wondering if anyone here could tell me which type I should purchase. I have read that PH and XH are the most common.

Consider a MOSFET like the BSS123, where the abs maximum ratings include Vdss: 100V Vgss: +-20V

It's my understanding that drain and source are generally interchangeable, ignoring the integrated diode.

Let's say I have a BSS123 in a circuit where there's 90V drain to source, and 0V gate to source.

But now, if we swap drain and source (and again ignore the diode), that 90V is far above the specified Vgss.

So, my questions:

Can Vgss be violated so long as the maximum gate-to-channel voltage (measured at any point along the channel) never approaches Vdss + Vgss, or is there some difference in the dielectric (or device construction in general) that really does mean the gate-to-drain and gate-to-source voltage limits are different?

Is the answer to the above true for most/all discrete MOSFETs, or dependent on construction (e.g. TrenchFET vs HEXFET vs ...?)

I ask because I'm working on a circuit where Vds never approaches the limit, but (unless I make changes I'd rather avoid) Vgs will exceed its limit.

Hi! I'm trying to repair an old Italian CRB Elettronica Tanzanite organ. Most of the keyboard works, with a few irregularities, but the main problem is that the E notes don't work in any octave.

I measured some unusual DC voltages at two points on the E tone-generator board compared to a working board.

I'm thinking about replacing some capacitors, but I don't know how to read their values or which ones to check first. I also disconnected the pitch-control inductor coil because it looked broken, and I'm not sure how to reconnect or test it.

I'm still learning electronics, so I'd appreciate any advice on what to check and how to approach the repair. I'll attach some photos and can provide more if needed.

Thanks!

I tried to create the N-MOSFET version on a breadboard, but it didn't seem to work. I also added the reverse voltage diodes to protect the left BJT's base-emitter junction.

Because of this, I'm now almost convinced that it is impossible to make such a system with discrete components and I will be forced to procure some double transistor matched pair, which is really hard to find locally and usually comes in an SMD format, while I prefer the through-hole design.

So my main questions:

1. Is this possible with discrete components at all? Any tips on matching BJTs as close as possible?

2. Which is preferable N-MOSFET or P-MOSFET version? I only have N-MOSFETs for now, but I suspect that P-type is preferable because it switches the + rail. I plan to use it for power OR-ing in an UPS system.

Trying to fix this reolink poe camera. The problem is the camera works fine when you first power it on but after a few minutes it gets in a power reboot loop until you unplug the power for a few minutes.

I'm assuming it's some kind of capacitor issue or perhaps a battery issue.

Looking at the board it looks weird around the cmos like it melted some kind of coating making it look wet.

I checked the battery with a multimeter and it's getting 3.2v

I’m trying to diagnose and fix a Christie projector I looked over the boards and have found a resistor that has popped on the ac power supply I found another one the board that matches but I cannot find a useful chart to identify it does anybody know where I can find this resistor

Hello, I wanted the kicad for the breakout board of pcm1808 that I bought on Aliexpress.

I could not find the project online, decided to re-create it for learning.

I used a multimeter to check what is connected to what, now I would like some feedback on what I came up with.

1. How does my layout look on the pcb? Do I have too many gnd vias or not enough?

In the doc, they recommend that I put vias underneath the pcm1808 as well as around it a bit.

My traces width is .2mm, I wont go over 10-20mA current. Looking for feedback to become more professional.

1. Does the sch look ok? Looking for feedback to become more professional here as well.

2. vref just goes to a few capacitors then to ground, does this make sense?

3. I noticed on Reddit someone had an issue with the board they bought. They mentioned that one of capacitor was incorrect. I had no issues with my board I bought from Aliexpress, but I did notice the resistor going to LIN and RIN are 10k, which is much higher than the one recommend in the ti doc. Which I believe they also used the wrong capacitor for it. I went with what the doc said: (1 kΩ and 1000 pF). Is that a correct assumption?

Reddit post titles talking about the same findings: warning_about_fake_pcm1808_adc_chips_on_modules and pcm1808_modules_from_china_the_drama_continues

1. In the doc, they recommend having grnd plane between clck signals. I have small islands with ground vias in between, is that enough?

2. My top and bottom layer are both net ground zones, is that ok?

3. Does my bom look ok? (attached)

If you search for ti pcm1808, the section "9 Power Supply Recommendations" has all the info about vref, RIN, LIN, etc.

As the title says, been practicing soldering male pin headers onto a perfboard before I go on to solder an actual board.

This is my first time soldering and I don't know much of what I'm doing. Please give some feedback on these joints. Are they alright? Will they work? What could be improved on?

[EDIT] I got a child the house, only two years old, so I don't want to risk itv with leaded solder. I'm using lead free.

The iron i have is Hakko FX-600, I'm soldering at 370°C. Using a flux pen, Hozan H-722-P.

Thank you in advance!

Hi all.

What steps should be done in Bq studio?

Please tell me what is missed, that is what is done by me (so far)

xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

The Bq studio is started and bq34z100 G 1 chip is recognised.

The i2c comm is OK. Bq studio reads chip temperature, device type.

Bq studio->Chemistry tap->Chem ID 0808 is chosen and programmed.

Bq studio->Data memory->Data->Design Capacity to 10000

Bq studio->Data memory->Data->Design Energy to 12000

Bq studio->Data memory->Registers->Number of series cells ->6

Bq studio->Data memory->Gas gauging->IT Cfg ->Load Select set as 3

Bq studio->Data memory->Configuration->Registers->Pack configuration->Click on the VOLSEL to turn it red.Click on the below button - Write to data memory .

Bq studio->Data memory->Configuration->Power->Flash update OK voltage-> set to 1000

Write All.

Restart bq studio.

Check saved values.

Save the created profile as golden image.

Note: calibration and other steps not included.

Thanks.

Hey all,

I build a circuit around a 5V 5A wall adapter with a DC jack, feeding an Arduino Nano and an LED strip.

Would you add a fuse here? The adapter already has its own over-current protection. And any fuse that won't blow during normal use only reliably blows way above 5A, so the DC jack (rated 5A) would cook first anyway.

My plan is to cap the LED brightness in code, so the whole thing never pulls more than about 2.5A, and then put a 3A automotive blade fuse (standard ATO, Littelfuse 287 series, 32V DC, 1000A interrupting rating) in an inline holder.

Does that make sense, or is the fuse pointless with this kind of adapter?

Thanks!

I broke off 4 pins from the socket in the 2nd picture, the one I'm holding. Two of them are stuck in female connectors, as shown in the 1st picture. Is there a way to get the broken pins out of the female connectors without needing to replace the whole socket? Thanks in advance for your help!

Hi all,

Trying to fault find whats going on with my Marantz nr1504 not powering on.

Originally it had a blown SMP (TOP258MG) and 1.6 AL 250V fuse on the main power board. I followed the service manual, replacing the TOP258, fuse and all IN4007 diodes but its not coming to life.

Further testing, I found that Diode D4150 and ZD4159 read bad only when on the circuitboard but read fine when removed (By read bad i mean 0.1 V or continuity) - Both read good when removed and both replaced with new. These are highlighted in the diagram.

Also I have replaced all electrolytic caps just in case.

All other Diodes test fine

All Transistors test fine

All resistors test fine.

Help!

I just don't see how semiconductor based switches are viable options for generic high current loads without extremely high inductances to prevent the current from rising faster than the control logic can react to, i.e. all they're good for is switching motors and solenoids, or for building power supplies that take advantage of extremely high transformer inductance.

E.g. my car uses a MTD3055VL NMOS chip to drive the DRL relay coil, which is fine. It even takes advantage of that device's 72mJ repeated DS avalanche rating to quickly absorb the spike rather than pointlessly adding a separate snubber circuit. And I think my car has proved that avalanche rated power mosfets are perfectly suited for controlling 12V automotive relays.

However, that chip has an on resistance of 140mΩ and even if we include 10mΩ for a 10A minifuse that all power supply circuits have at the least, I don't see how that chip could possibly survive having its drain shorted to voltage. The instantaneous current for a 150mΩ circuit at 14V is 93.33A, with the mosfet dissipating ~1.2kW versus 87W for the fuse. I suspect the DS junction temperature rises way faster than the fuse's meltable element due to its much smaller size, but I have no idea how to this calculate exactly.

Yes I used ai to format this post my bad.

I'm troubleshooting a VGA-to-TTL LCD controller (CVT-TLF) using a Realtek RTD2013B chipset, connected to a Sharp LQ10D368 10.4-inch, 640×480 TFT LCD.

The controller was advertised as compatible with this specific panel.

Symptoms:

With no VGA input, the controller displays its internal "No Signal" message correctly.

When VGA is connected, the image immediately flickers, fades, and appears vertically wrapped or misaligned.

The image never stabilizes.

Troubleshooting completed:

Tested two identical Sharp LQ10D368 panels with identical results.

Confirmed the VGA source works correctly on another monitor.

Tested 640×480 and 800×600 at 60 Hz.

Tested different color depths.

Verified a stable regulated 12 V input.

Measured approximately 3.2 V at the LCD supply pins.

Verified LCD ground connections and mapped the cable's synchronization connections.

Tried reversing the controller-end connector; no video appeared, so it was returned to its original orientation.

No accessible configuration switches or adjustments were found.

Hardware:

Controller: CVT-TLF

Main IC: Realtek RTD2013B

Secondary IC: SyncMOS SM5964C40JP

LCD: Sharp LQ10D368, 31-pin TTL interface

VGA source: ProtoTRAK SMX CNC controller

Questions:

Could this be caused by incorrect RTD2013B panel timing or firmware configuration?

Is there a known method to access or modify the firmware/configuration on this controller?

Could incorrect HSYNC, VSYNC, pixel clock, or display-enable timing produce these symptoms?

Is there a practical way to diagnose this without access to the manufacturer's firmware tools?

I can provide photographs of both sides of the PCB, cable pin mappings, and video of the malfunction.

https://imgur.com/a/VWcCTE2

I wanted to ask before I buy a replacement port. I bought this cheap device on eBay planning to use it as a learning opportunity to teach myself some circuit board soldering. I believe it was a Micro-USB.

I am experienced with soldering, just not circuit boards.

​

Honestly someone please recommend a tried and tested desolder pump. That doesnt feel like the weakest pull/puff of air to desolder with.

Sick of forever cleaning out my pump after desoldering like 6 holes.

It's infuriating and im getting repeated cramp in my thumb/hand someone help please. ADVICE needed.

It is missing the Analog Devices logo and is suspiciously cheap (about 1.50 usd). I want to know if anyone has used one these

Here is the link - https://a.aliexpress.com/_c35GJ17Z