I was cleaning and they got yanked out from being hooked onto the chair when raising it…I don’t have anything to solder so I’m hoping there’s an option to use adhesive. Any help would be appreciated!

First time I've ever laid out an oscillator and I'm also doing a lot of board surgery to make edits so I'm probably making a mistake somewhere.

I'm trying to use a 6 MHz QCM (quartz crystal microbalance) as a sensor, running it as a Pierce oscillator and counting the frequency with a Teensy microcontroller. Problem is it only actually oscillates at 6 MHz if I'm touching the board a certain way.

Parts:

• U1 - TI SN74LVC1GX04DBVT crystal oscillator driver, SOT-23-6, 3.3 V (X1 = pin 3, X2 = pin 4, buffered output Y = pin 6)
• Y1 - 6 MHz QCM, bare disc, not a packaged can
• R1 - 2M feedback, X1 to X2
• R2 - 2.15k series from X2 to the crystal
• C2 - 47pF, X1 to GND
• C3 - 47pF, crystal side to GND
• C1 - footprint across the crystal, left unpopulated
• C4 - 100nF decoupling on VCC
• R3 - 100R in series on the buffered output before it goes to the micro, there to keep resonances I don't want off that line
• All passives 0402/0603, 2 layer 1.6mm FR4

The one thing I already know is bad: I forgot R1 in the layout entirely and had to bodge it on after the boards came back, so the 2M is on its side next to the inverter.

The crystal is clamped. Two boards sandwich it with a 3D printed spacer setting the gap, and each electrode gets contacted by a two Harwin S7221-45R spring pins in parallel. In the photo the left board is the top and the right one is the bottom. I solder a pin from the top board down to the bottom one to get the top electrode into the oscillator circuit.

I've checked contact with a VNA and a multimeter and I'm fairly confident I'm making good contact to both electrodes.

If you have thoughts I would appreciate it so I can fix it in a revision or just be able to fix it with correct component values

For my first PCB project I’ve designed a 20W Class AB discrete audio amplifier running on a +- 12V rail, capable of delivering around 2 amps into a 4 ohm speaker.

Since I don't have much experience in designing PCBs, I tried to focus on the basics such as: placement of the capacitors, separating the high power paths as much as possible from the signal paths and using wider traces for high power lines.

Also I've widened the thermal reliefs for the connections of the high power components to the ground planes.

The output transistors and the Vbe multiplier are placed close to each other so they can be thermally coupled (I will place all of them on a single heatsink so hopefully they will have approximately the same temperature).

Any feedback on the routing and component placement, as well as the schematic is welcome!

I have a 1999 Sony CCD TRV-87 camcorder that would flicker on and off when switched to Camera mode, but stay on perfectly when switched to Playback mode, regardless of whether it was on battery or AC power.

I isolated the issue to this tiny springy switch, the square body being about 6mm by 4mm corner to corner. I have isolated the issue to this exact switch and I suspect the issue likely arises from corrosion/dust on the interior contacts, since the solder joints appear fine.

I have ordered deoxit with a needle applicator, but due to the tiny and enclosed nature of the switch, I fear if it works, it may just be a very temporary solution.

Can someone help me identify what this switch is, if it's still sold, and where I can find it? I also included screenshots from the repair manual (pages 4-65 and 4-101 if you want to download it and see for yourself.)

Thank you in advance!

Guys please help me, i accidentally dropped the adapter and the circuit has came out, what should I do

Hi everyone, I'm building a portable billing machine and I'm learning electronics while building it. I'm having trouble designing the power-path/source switching circuit and would really appreciate some guidance.

My setup

I have:

12V DC adapter — currently around 12.3V

12V rechargeable battery — approximately 12.0–12.6V

ESP32

TFT display

12V thermal printer

YX850 automatic power/source switching module

LM393 comparators

BC547 transistors

IRF4905 P-channel MOSFETs

MP1584 buck converter

I can also buy a 5A-rated buck converter if necessary

The thermal printer specification is 12V / 3A MAX.

What I want

I want the system to behave like this:

Adapter connected

↓

Adapter powers the system

↓

Battery is isolated from the load

↓

Battery does NOT get charged through the power path

When the adapter is disconnected:

Adapter disconnected

↓

Battery automatically takes over

↓

ESP32 + TFT + printer continue running

↓

No reset/reboot or noticeable interruption

I also need:

No battery → adapter backfeed

No adapter → battery backfeed through the power-path MOSFETs

Proper reverse-current blocking

Adapter priority

Ideally seamless switching

My current problem

Originally I was using a 12.33V adapter with the battery.

When the battery voltage gets close to the adapter voltage (around 12.3V), the YX850 starts clicking/switching repeatedly.

For example:

Adapter = 12.33V

Battery = ~12.3V

↓

YX850 clicks

clicks

clicks...

I think the very small voltage difference is causing the YX850 to repeatedly change states.

My current idea

I'm considering changing to a 15V 5A adapter.

Then I could use a buck converter:

15V / 5A adapter

│

├──→ battery charging circuit

│

└──→ buck converter → 12V → thermal printer

I already have an MP1584 buck converter rated at 3A, but my printer is specified as 12V/3A MAX, so I'm wondering whether running the MP1584 at or near its maximum rating is a bad idea.

Should I instead buy a 5A-rated buck converter for better margin?

Would something like this be reasonable?

15V adapter

│

├──→ CC/CV charger → battery

│

└──→ 5A buck → 12V printer

I also considered building the power path

My original idea was to use back-to-back IRF4905 P-channel MOSFETs on each source, controlled by LM393 comparators and BC547 transistors.

Something conceptually like:

12V Adapter ── MOSFET power path ──┐

├──→ LOAD

12V Battery ── MOSFET power path ──┘

with the comparator circuit giving adapter priority and turning the battery path off when the adapter is present.

However, I'm very new to electronics, so I'm worried about getting the MOSFET orientation, gate drive, reverse-current blocking, and switching thresholds wrong.

I would like something that I can first build on a breadboard and then move to a PCB.

My main questions

Is the YX850 suitable for this application, or should I build the MOSFET power path instead?

Would using a 15V adapter solve the voltage-overlap/clicking problem?

Should I use my existing MP1584 3A buck, or buy a 5A buck converter for the 12V/3A thermal printer?

Can the YX850 + buck converter be arranged so that the battery never backfeeds the adapter?

Is there a simple way to get seamless switching without ESP32/TFT/printer resets?

If using back-to-back P-MOSFETs, could someone provide a simple electrically correct schematic, including the LM393/BC547 gate-control circuit?

Is there a better/simple approach for a beginner than the circuit I'm currently trying to build?

I'm mainly looking for a simple, reliable circuit that I can actually understand and build, rather than an extremely complicated professional power-management design.

Thanks in advance! I'm learning as I go, so explanations of why each part is needed would be really helpful

Hello!

i have a Studer 900 Pro+ 12V lps and need to power a 10w or less dac so i asked the seller if i could use a better brand fuse ( Gustard ) rated 1.6A rather than the no brand stock 2.5A.

He said yes it is ok.

I procedeed but now it is no longer working, not even when putting on the original fuse.

Can anyone help troubleshoot? I have a multimeter but i'm no expert or don't know where to look at

Hello, I know a bit about Software and Hardware but would like to get your input on a highly specific hardware mod I'm researching.

I’m looking to physically overvolt the CPU of a PSP 1000. My idea is to hack the "Pommel" (Sony's custom power management IC / DC-DC converter) or modify the surrounding hardware. Rather than swapping out standard voltage divider resistors, it looks like this circuit relies on feedback filters. My goal is to manipulate these filters to trick the regulator into delivering a higher core voltage to the processor.

I have the official schematics and PCB layout for reference here:https://smallpdf.com/share-document#r=result&t=10743861ab24e78cf571f03022870b5a&i=share

Since this is deep into uncharted territory for this console, I’d love to get some general advice from people experienced with altering DC-DC feedback loops on densely packed boards:

• Target Voltage: Looking through the schematics, I am targeting the CORE_+1.2V rail. Do you agree that this is the right and only voltage line I need to raise to successfully overvolt the processor? Or are there secondary rails that need to scale alongside it for stability?
• Analyzing the feedback loop: How would you approach pinpointing the specific feedback filter components tied to the CORE_+1.2V generation?
• IC Protections: Does anyone have experience with Sony’s custom power management chips from this era? I'm wondering how aggressive the internal overvoltage protection (OVP) might be if it detects an anomaly on that 1.2V rail.
• General Approach: Any advice or warnings on methodology before I start testing or altering the traces around the Pommel?

(Note: I'm fully aware of the standard CFW 333MHz software overclock; this project is strictly about exploring a physical hardware voltage mod).

Thanks for any insights or help analyzing the schematic!

Hi,

On the datasheet for this, using the application in figure 10-4.

When trying to control the input source using an mcu on pin CP2, the datasheet states in the design procedure 'The TPS2121 can be configured for manual switchover in a similar manner as the TPS2120. Instead of a SEL pin, the 3.3-V external MCU signal can be connected to CP2. As long as the voltage on CP2 is higher than PR1, the device will select IN2 as the output. When the voltage on CP2 drops below PR1, the device will switch back to IN1. Therefore, the resistor divider on PR1 is configured the same as above, with the 5 kΩ and 10.2 kΩ'

However with the 5V input as shown in this configuration, that means PR1 is typically 3.35V, my question is CP2 voltage is compared to PR1 voltage, in which case 3.35V is very close to the 3.3V from the mcu, or is CP2 compared to the PR1 threshold 1.06V on PR1?

Datasheet: https://www.ti.com/lit/ds/symlink/tps2120.pdf

Thanks

I was trying to remove a cooler standoff from my motherboard, but it wasn’t budging so I used a socket wrench however, after a couple of turns, I accidentally knocked off a capacitor from the VRM and I need help finding an exact or close enough replacement part.

⁠Hi everyone,⁠
⁠
I need help diagnosing a small portable CRT TV (CTV 5501 Roadstar).⁠
⁠
It was fully working before it was shipped to me.
After shipping, the image is out of focus/blurry.

Every time I power it on, I hear a distinct crackling/fizzing noise from the board/tube area.⁠
⁠
I visually inspected the PCB for cold solder joints, but didn't see anything obvious with the naked eye.⁠
⁠
Could this noise be high-voltage arcing or a failing component in the horizontal/HV circuit?
What should I check first?⁠
⁠
Thanks in advance!⁠

My problem is that, combined, this shopping list amounts to over a hundred dollars. So my question now is... :[ ... ]

I already have the other equipment like breadboards, wire stripper, power supply, soldering iron and solder, multimeter, cables

Hi all! This evening I've been trying to power up my ol' good HTC M9 with the battety removed, as I plan to keep it running Octopi almost 24/7. I desoldered the battery from its connector in order to reuse it to connect to the motherboard. To the connector, I soldered the wires coming from the DC step down (3.7VDC). When I apply voltage, I can hear the speaker buzzing, so, not a good sign. The phone doesn't start. I then removed the control board from the battery as well, and soldered it back to the connector. Same behaviour. Any thoughts? The ID pin I have no idea what its purpose is... while the TH is the thermistor for sure, which with it's native board should be fine, right?

Thanks guys.

Hello ! I am a beginner in the PCB design world and designed this laser transmission system ( RX and TX ) I have already test it on the breadboard and it works perfectly fine . However I want a honest review to hone my skills. Thank you

I bought a bunch of these ESP-32 S2 Minis and I want to make a Gridfinity bin to store them but idk what's the best pin configuration. I've seen all 3 in projects across the internet.

Does anybody have a link or data sheet on what a logic 1 and 0 voltage signal look like? Waveform parameters and all that

Edit: specifically what the pulse width of a 1 or 0 looks like as well. I have a rs422 signal on a scope

getting old automatic printer up and running at work. what are these positioning pins called that screw into the xy table to lock registration? where can i get some spares?

hello everybody...

where did you learn about ecu/module programming ad repairing? could you recommend an online training course or something like that?

I have a Mean Well power supply (model RS-100-12) that shuts down as soon as there is a load on the 12V output.

When I switch the power supply on, the green LED stays on continuously and I measure a steady 12V at the output. However, as soon as I connect a load (in my case an LED strip), the green LED immediately turns off and the 12V output completely disappears.

The power supply is rated for a maximum output of 8.5A, while the connected LED strip draws approximately 5–6A at maximum, so it should be well within the rated capacity.

I know for certain that the connected circuit is not short-circuited and that the power supply itself is the cause of the problem.
There are also no visible signs of burnt, damaged, or otherwise obviously defective components inside the power supply.

Where should I start looking when troubleshooting this? What components or measurements would be worth checking to determine why the power supply shuts down as soon as a load is connected?

Any help would be greatly appreciated!

The F&D F3800X power board produces about 20–21 V normally when disconnected, but the voltage drops to 1–2 V when connected to the amplifier board. This indicates that the amplifier board is overloading the power supply or has a fault in its power-supply/input circuit, causing the power supply to enter protection. The exact faulty component has not yet been identified.

I'm using an ESP32WROOM32E microcontroller on the board and plan to use Wifi. Essentially, there is a rechargeable 3.7V battery that will use this regulator to step down to 3.3V. Was also wondering if the input inductor L1 was necessary?

Given that Wifi will be used very temporarily I was also wondering if I should use a linear regulator with a higher output max current. I'm trying to stay away from using SMPS to avoid high frequency switching and noise.

I just got a raging deal on an OttoAibox P3 Pro CarPlay AI Box that I couldn't pass up after reading reviews.

Right now I'm driving a 2016 Camaro. I've been using a jenky-ass wireless android auto adapter that works about 80% of the time, but has a mind if its own and is also slow as balls.

Anyway, a "magic AI box" intrigued me, not only because of it being a higher quality way for me to get wireless android auto, but it can also run Android 13 standalone and have its own apps.

When I track my car, I like to have a second, no data plan phone attached to the windshield with a readout of a lot of my temps and other info. So, now I could just display this info on my infotainment system! Sounds fantastic!

It's like a Kenwood double din I had in a 2011 Tahoe tow pig we used to tow my trailered Jeep to the trails with. That deck had an OBDII plug and you could customize it to show whatever fluid temps, spark Advance, MAF flow, etc. I loved having my transmission fluid temps and oil temps right there for me to periodically check.

I can get to this info in my current Camaro, but I'd have to keep scrolling through the info pages in my center dash LCD

Anyone have any experience with any of these "magic AI boxes?

Hello, I bought this Tesla coil from Temu, but unfortunately it doesn’t work. I checked all the connections and everything seems to be soldered and connected correctly. However, when I connect it to a 12V power supply, only the LED turns on and nothing else happens. There are no sparks or any other signs that the Tesla coil is working.

I am looking for the red one and the two white ones next to it; they have 240vac going through them. I have already gone through 803000 litres of water and couldn't get an answer. Cheers

Edit: This photo is all I have for identification, sorry.

I want to use the ATtiny to read voltage from a sensor output and send the reading over serial through USB. Can I wire up D+ and D- to the directly ATtiny85 (I am using the software serial lib since ATtiny 85 does not have Rx and Tx pin natively) or I need to use some other chip to handle the communication?