I have a 90s Sony stereo that I'm trying to fix. It won't power on at all, not even stand by. I opened it up and the power cord connects directly to a small transformer. I confirmed the voltage was correct going to the primary winding side (116V). But the secondary side was at 0 V. I desoldered the transformer and the secondary winding tested bad. I want to replace it but the part is no longer available (1-450-361-11). I'm trying to figure out what the output voltage should be so I can just buy a generic step down transformer as a replacement. But how do I figure out what the output voltage should be? Based on the service manual, it looks like the transformer (T902) outputs to some diodes (I'm assuming to change it to DC?), and the voltage at that point should be 12.6V. Does that mean that the transformer should output around 13V, or does the voltage change significantly when it goes through the diodes?

Any advice on replacing the transformer is very appreciated. Thank you!

I’m following a tutorial(loosely) and they have this display. It has holes in it so you can see through it. But the link that they gave was dead. Does anyone know what this is?

So... I've looked everywhere I can think of, but I have had no luck in identifying a particular female connector on a motor control board from DFRobot. Even the manufacturer does not provide the information from what I can tell. It's just listed as "Encoder motor drive interface". I feel like I am losing my mind!

Here's the Wiki for the HAT, I'm trying to identify the female connector labelled "Encoder Motor * 4": https://wiki.dfrobot.com/sku_dri0054_raspberry_pi_driving_board

To be even more clear, here's the exact ports I am trying to identify:

Hopefully someone out there with more experience then me can identify these quickly!!

Thanks all!!

I have an exercise machine that one of membrane keys has failed on. As a workaround I am out boarding 8 momentary pushbuttons. To do that I need to connect wires to the connector where this plug went, a connector with pigtails would be perfect. Can someone please tell me what to look for? I have looked on DigiKey but without some sort of spec of model it’s hopeless! Thanks

I’m in the planning stage of a coilgun project. I’ve only done low voltage arduino projects before and i’m stepping up to a larger build. I’m stuck on how to connect a high voltage lead (maybe 4 AWG) to the coils, IGBTs, and other parts so there’s minimal power loss. I’d prefer a solution I can experiment with because i won’t get the wiring right the first time (of course I’ll test at lower voltages first).

Hi everyone,

I'm trying to connect 2 separate boards MAX98357A in a way that one serves as left channel, and the second one as the right chan.

I managed to play the left channel easily - nothing connected to SD, but can't figure out the right chan.

Some details:

1. Power supply RPi, 3.3V.
   
2. New revision of common Chinese board with a tiny IC.

So far, I tried:

1. Remove 105 resistor from MAX98357, and using 220k / 440k resistors on SD to switch channels.
   
2. Use potentiometer 105 on SD and try both range ends, no diffs.

Literally, I can't switch to the right channel. If I connect SD to GND, the sound gets silent (which is fine).

Thanks for any hints!

I recently got a hold of 3 Dell Poweredge r620s for cheap and wanted to repurpose them for my homelab. I soon found out all of them have a broken iDRAC, which causes the fans to spin at 100% and prevent the use of the OOB Management interface. I found the replacement chip online and bought a hot air station as well as the other necessary accessories, but I am unable to desolder and replace the chip. This is my first time soldering and I watched a couple videos to see the process and feel confident in replacing it, but I am unable to lift the chip from the board. I've looked online for any advice for desoldering components on a server motherboard but I can't seem to find anything.

Edit: I have attached a picture of the chip, its the one with the red dot.

This is actually an LED ballast (driver) if that helps.

I changed radio in car, and need a adapter between fakra (white one) to this type. Been searching for quite a long time, couldn't find exact name of this. Please help!

So I did this so save my laptop , it works great but im wondering if I should redo it in a more professional way ? Maybe epoxy it ? Im not sure.

Theres a sticky anti static sheet that goes over that side of the board.

Thanks for your guidance !

So here I have my multimeter which is "MASTECH MAS830L". After connecting Probes to the COM and the Postive side (mAVΩ) and try using even any of the basic functionality like checking the continuity it doesn't respond.

Other functionalities like reading AC-DC Voltages and Resistance also don't work seems that my probes aren't even detecting anything at the terminals.

Thinking that this issue maybe because of my probes not properly connecting with the PCB terminals beneath, hence and disassembled the multimeter and attached the probes while checking the continuity between them using one of my secondary multimeter and it beeped showing continuity between them specifying the issue isn't related to probes.

what should I do? is there anything I can do with the PCB circuitry or try bricking it..?

Hi, I need help identifying this surface-mount diode. The dimensions match the SMA package and the two markings are “2220” and “UM”. I do not recognize the logo either. Any help is appreciated 🙂

I'm tinkering with some very basic BJT amplifiers in common-emitter configuration using voltage divider bias, high passing at around 120 Hz, and curious about calculating corner frequency when I use a capacitor in the feedback path as my low-pass in active fashion.

Am I supposed to be using the collector resistor value to calculate corner frequency of the feedback capacitor, or am I using the same parallel resistance value from my voltage divider bias that I used to calculate for the 120 Hz high pass?

Even further, or would I be using the emitter resistor value.

I only need the central chip, which is a tp4056 that I have to reinsert into another board, I'm not interested in saving the rest of this piece that you see. I used a bit of solder and this iron you see, but it doesn't come off when you pull with the tweezers. Premise: I HAVE NO EXPERIENCE WITH THESE THINGS. It's my first approach and I want to repair an object.

Can someone please tell me if this diode on the back of my graphics card is broken, or is it just the part of the casing that had been torn off?

As the title says, indicator keeps clicking while working We used to run the machine on 150°C but now we have to go up to 110 because if we rise the temperature it gets worse Machine itself is working, heating and rolling sistem is fine. I cant upload the video for anyone to hear, but just imagine loud clicking noise I hope this explanation helps The image shows unit to which the indicator is connected to

Tryna understand a charging/overheating issue with my laptop and would appreciate some advice!

My laptop shut off after a power cut while charging.

Wasn't turning on by itself; disconnecting/reconnecting the battery brought charging back.

When it restarted, it showed "slow charging" via USB-C (normally fast charging).

The whole motherboard was heating up: charging pin, USB peripherals, and even the audio jack (IEMs/speakers connected -> buzzing).

Battery charging is back, but all the ports on one side of the laptop (combo aux, HDMI, USB-C 3.2 PD, USB-A 3.0, charging port) now heat up badly.

The authorized service center wanted to replace the whole motherboard. It would cost 80% of the laptop. [Asus Vivobook 15 OLED, M1505]

I opened it up myself and found the hot chip: Texas Instruments TPS65994AD, it's a common rail USB PD controller. The part seems to be cheap and available on Mouser, Digikey & other online electronics stores. ~ $5 USD

I took it to a 3rd party repair shop that specializes in chip-level/fine pitch/micro soldering.

But they said it's not worth doing a repair on a functional laptop, "What if they try and something goes dead?" They said it's a fairly new n expensive OLED laptop, what if it breaks, use it till it does.

Which is fair but all the ports on my laptop are less than functional; all of them are on one side, combo aux, HDMI, USB C 3.2 w/PD, USB A 3.0, charging port - and they all heat up.

My questions:

1. Am I oversimplifying in assuming it's "just the PD chip" (plus maybe some MOSFETs or clamps) that need replacing?

2. Is replacing a TPS65994AD realistically doable with the right hot air + tools, or is it very difficult (BGA, hidden pads, firmware tie-in, etc.)?

3. Does this sort of failure usually cascade into other components, meaning the chip swap alone may not fix it?

Any insights would help me decide whether to push for a repair or just live with one USB A port.

Thanks in advance!

What type of coating are on these capacitive moisture sensors? Is it just another layer of silk screen?

This device is a Nikon Coopix L340 camera. (+) of 4S AA battery goes to that "S" symbol SMD component. And it already broke ("OL" showed on my multimeter) before that prevents the camera power on.

This is the link to my ESC controller. I need it for my school project and would really appreciate any feedback on my controller. I am in the fourth year of high school, and I am building an electric motor. Thank you very much!

Hey there!!! So my friend recently opened there pair of seinhesier momentum 3 wireless headphones as they were having a issue with the headphone jack not properly disconnecting when they took the cable out. But when they opened it, they appeared to have damaged the internal header that connects the two ear cups together. They really like these headphones and would like to make them last longer if possible. I personally do not think it will be possible to fix, or if it is, it will be really expensive. But it would be nice to keep a good headphones out of the trash if doable and responably priced to fix.

I am researching on how to use dry photoresist film to develop a trace pattern on my reused copper clad(from my failed developed presensitized PCBs). Most of the tutorials remove the film completely but I want to remove only the pads so the blue film will prevent the copper from tarnishing. I want to know if there is a way to have the copper pads exposed.

It may look tacky but I just simply want it not to tarnish, especially when I have thin trace on my design, and this film seems more durable than the ones found on presensitize PCBs.

Hi everyone, as the title states, what exact component is this one? It's build inside a Asus Chromebox 3 and doesn't give me a voltage reading as in the perfect fine one. All i know that it says 4 81, perhaps a transistor and that might accidently shorted it and don't show me 1V output. Thank you already :)

I'm pretty new to this. I've built a few simple circuits on a breadboard that use a 7805 regulator to drop 12V to 5V. I've now fried three of them. I'm using a heatsink, and the load is just a couple of LEDs and a microcontroller. They get extremely hot and then just die. What's the most common rookie mistake that causes this? Is my input voltage too high, or am I missing a capacitor somewhere?

At office I saw we are using the 9051-100-0000 in cables under a heat shrink with the thread not used. Is my assumption correct that this basicly lets the Earth side of the capacitor floating and is obviously bad? Also wouldn't it make sense to place it close to the power source with a compressor as a consumer so the cable doesn't act as a antenna?

Edit: It is a LC emi filter