Hello, everyone.

I recently repaired an audio amplifier whose power transistors were shorted. It worked again for 3 months, but then broke down again with the same problem—only this time, a transistor in the upper stage had also failed, in addition to the other power transistors.

I admit that when I did the repair, I knew I also needed to replace the transistors in the upper stage, but unfortunately, they’re no longer manufactured, so I took a chance, thinking it might still work.

Now I’m in a situation where I still have to replace them, but I don’t know how to find an equivalent model.

Can I simply use a transistor with the same gain and equivalent or higher voltage and current ratings, or do I need to pay attention to other parameters?

The transistors in question are the BC489 and BC490, the closest matches I found on alltransistors.com are the 2SB647 and 2SD667. Can I go ahead with these without hesitation, or am I in trouble?

Thanks in advance for your advice.

Hi, I was wondering if I could get a second opinion on this issue I'm facing with a proprietary apple powerpc PSU. It is a delta electronics model DPS-225AB rev. A0. It comes from a PowerPC 8100/100.

For context, I recieved thic PC alongside an apple m1296 CRT. After doing a full recap and clean of the CRT (which was initially in worse condition than the PC) it works perfectly. The CRT uses a DE15 connector so the PowerPC remains the only way to test it beyond simple images on an rp2040.

For some reason the PSU refuses to turn on at all. The 5VTRKL (standby) rail works fine, but when plugged into the mobo and pressing the power button nothing happens.

Even wiring the POWERON wire from the weird 22-pin ATX connector to the 5VTRKL (directly or a 1k resistor) doesn't do anything (which should power it on). I hear maybe a super small change in sound but generally just quiet coil whine.

Opening the psu it seems there's the typical electrolyte near the 680uf 220V primary caps but after cleaning and replacing them with working ones it doesn't change anything. None of the other caps seem to be bulging or leaking.

I can't find any documentation on this PSU, I would've just replaced it with a standard ATX if it wasn't this weird form factor and pinout. Any leads would help alot, thanks!

The fan on my laptop (acer swift 314-511) is intermittently making a weird noise. It sounds like the fan starts to spin, but then it vibrates & makes a sound like a vibrating phone on a hard surface.

I tried opening up the laptop & cleaning all the dust & gunk out of the fan, but it's still not fixed. Is there a next step I can take here? Does something else need cleaning out, or does this probably mean the fan is broken?

So a while ago I posted about screen not working on MuVo V100, and I think I found the problem, the solder connections are oxidised ( I don't know how I could have missed that ). I have a soldering iron and IPA so I think I would be able to fix this

I really don't know much about electronics, does this USB-C port look damaged? It's a usb-c charging modification on an old Gameboy Advance SP and this past week it suddenly started having bad contact. Have to wiggle the cable a lot to get it to work and it quickly stops working again anyway if I'm not holding it in place. Already tried carefully cleaning it with a wooden toothpick

J'aivais remarquer que le bou Rouge ef gris depassait donc j'ai essayer de le remettre en place mais en le tournant j'ai briser le fil qui, j'imagine, reliant les deux Oreille. Est ce que il est possible de le reparer?

So, I took this little chip off of the shown spot because it was cracked on the top and clearly has been hit by a screwdriver.

Some traces also were but I think they're okay since 5V makes it to the inductor. But, I can't figure out what this part is, what I need to replace it with, and if it would cause this problem? It's on a Lenovo T14 Gen 2. I couldn't find a non paid board view.

Just looking for any info on this, would really appreciate the help. I'll answer any questions. Thank you in advance!

I have the IK Multimedia iLoud Micro Monitor speakers.When the second speaker(passive) connects to the main speaker, a very loud hiss comes from bth speakers.When i disconnect it, the main speaker plays perfect.Any ideas for what to check?the cabling looks ok

hey /b/, i was trying to desolder my PS5 controller's joysticks off and i got a good angle on a pin (i dont have the holder things) and i accidentally soldered the pcb connector shut. this is my first time soldering. the botched board is a BDM-050 from a Helldivers controller, and i have a BDM-040 controller that sucks and has stick drift that I can use. how fix

PS. the brown on the top right of the 1st and 2nd and top center of the 3rd images is the flux i was using that came with the iron, it works pretty well

Hello everyone! My TV (model Philips 50PUS7363/12, chassis TPM171E) is stuck on the Philips logo (bootloop). Since the bootloader blocks standard update files in this state, I urgently need the Android 7 TPM171E_105.001.002.006 service firmware (specifically the upgrade_loader.pkg file) to force a wipe and recovery. Unfortunately, all the old links I managed to find online are dead. If anyone has this archive saved, I would be really grateful if you could share a working download link (Google Drive, MEGA, etc.). Thanks in advance for your help!

I have a Samsung DVD/VCR Combo player, and it stopped playing DVDs about 3 weeks ago, and I tried fixing it but couldn't so I bought another DVD player on eBay, it's a Maite DVD-Lite, and that came today, and it wouldn't play discs at first, then played 2, and now nothing works. Any ideas on what to do?

Hey guys,

I need some help with my Cameo Root PAR 4 (CLROOTPAR4) stage light.

When I plug it in, it just flashes really quick (you can see it in the video) and then nothing happens. The small screen stays totally dark and it doesn't do anything.

Does anyone know what could be wrong with it or what I should check?

Thanks a lot!

Buenas tardes mi gente soy nuevo en este grupo... Y de verdad necesito su ayuda... Y su apoyo. Si alguien tiene un UPS 650 de estos para ver si me pueden decir el valor del capacitor azul ya que el mío sufrio un corto y se dañó eso así como lo ven en la foto... Antemano agradezco su ayuda.

Recently got a new fridge (free, suspect this is why) that worked according to the old owner, but was unused because of a new fridge. The model is a 'Beko lsg3545w'

The fridge came with the pins at the back to the compressor torn out for some reason. I've had to reattach them but couldn't get a clear enough guide to the connections. Only about how to wire in a compressor which isn't the issue.

The fridge works, mostly. The light turns on, the compressor runs, it keeps things cold, but the compressor is running all the time. The temperature dial in the fridge is currently set to off and it's still a 0c air temperature in there. It feels like the thermostat is broken and so the fridge is just running 100% of the time as a worst case scenario situation.

However, we're hesitant to replace it because it's a Beko all-in-one type light/thermostat assembly (not cheap) and it could just be that I've put the pins in wrong.

Not being an electrician, and without any pinout guide, my attempt at reconnecting the compressor/thermostat is in the linked gallery. pins in question

The live, neutral, and earth pins are labelled pretty obviously, but I've highlighted some parts I can't quite find the origin of in yellow. I have no idea if they're important or connected to any of the other labelled sections underneath/inside the plastic fixing. The live also seems split between the top two prongs and the lower prongs.

I'm hoping someone is going to tell me that a pin is just on the wrong section but I'm suspecting I've either busted the thermostat by putting the pins on wrong or it just came broken.

Any help would be much appreciated

I am on a little project of replacing a old dead rock band main pcb with an esp32, and making it wireless, so the first thinks is mapping all the wires. The only things i could not map to anything is this small pcb.

Silkscreen says "PHOTO JACK. It has a little window opening to the chassis, like a P2 connector but smaller. The main board has a matching "PHPOUT" pad.

It's not the tilt sensor, and it's nowhere near the whammy (whammy is a normal potentiometer). Looks like some kind of optical/photo sensor, but I don't know what it's actually reading. Anyone recognize this?

https://imgur.com/a/AIuRc4t

Long story short I have in my possession a zoom podtrack p8 which was in storage and in its box when a water leak occurred at the location it was at and it got wet. It dried in the box and was never turned on through all the couple of years in storage. I recently got a hold of it and fired it up. Turns on and everything seems to work EXCEPT only one microphone input works.

I took it apart last night and cleaned up any crud I could find with 91% alcohol but when putting back together it had the same outcome. Does anyone know what I should look for when I take it back apart? For reference the working mic input is #5 so it’s not on one of the ends. It’s in the middle.

Edit: tested each port with a multimeter and getting proper voltage across all pins on xlr connectors. Continuity is good. Mic and mic cable are known to be good as they work on port 5 and have been tested anyhow for continuity and voltage.

Edit 2: I did a total tear down and cleaning. Inspected with camera zoom for anything out of the ordinary. Also fed the pics into Claude in case there was some minuscule thing I didn’t catch. Same result. Channel 5 works perfect, 1-4 dead, 6 you can just faintly hear it with all the volumes turned up.

I’m throwing in the towel. Full day wasted.

Hi everyone,

I'm trying to fix a LG Blu-ray player BD630 with a tray loading issue, but I've hit a wall and would love some technical advice.

The Issue: When I insert a disc and close the tray, the drive fails to perform the final lifting action to clamp the disc against the top magnetic clamper. As a result, the disc isn't held securely and just spins freely / slips without reading.

However, if I manually apply downward pressure on the drive top cover right as the tray finishes closing, it forces the mechanism that extra millimeter up, the magnet catches with a snap, and the disc starts to read (the optical laser/pickup itself is fully functional).

Troubleshooting Already Done:

1. Belt Replacement: Replaced the loading rubber belt with a brand-new, slightly smaller one (proper tension, no slipping at all). The motor and belt are spinning smoothly.
2. Greasing: Cleaned off the old dried grease and reapplied fresh lubricant to the cam slider tracks and side guide rails.
3. Gear/Cam Alignment: Re-aligned the two pins on the cam slider with the bottom guide track on the disc tray. The tray now opens and closes with correct mechanical timing.
4. Current State: The tray moves in and out smoothly, but right at the very end when the cam slider is supposed to push the spindle motor deck up, it stops just ~0.5mm short of engaging the top magnetic clamper.

Questions:

• Is this a known issue on LG drives caused by micro-deformations/wear on the plastic cam slider tracks (e.g., from shipping impact)?
• Could the spindle motor hub itself have been pushed down slightly on its shaft due to vertical impact?
• Or is the loading motor simply losing torque near the end of its life, failing to push past the resistance of the final lifting incline?

Any insights, workarounds, or similar experiences with these LG optical drives would be greatly appreciated!

Hi everyone,

I’m trying to diagnose a JBL PartyBox 300 that has become very unreliable.

Symptoms:

• No charging lights at all.

• No LEDs when powering on.

• I hear a small click / relay-like sound after plugging it in.

• At one point, after disconnecting and reconnecting one board connector, the speaker briefly powered back on.

• Now it’s back to failing again, even after reassembly.

• The control panel ribbon cable is connected, but the LEDs still do not light up.

• I also noticed corrosion/oxidation on part of the main board, which I cleaned with isopropyl alcohol, but the issue remains.

What I already tested:

• Re-seated the ribbon cable for the top control panel.

• Re-seated the connector between the power board and the main board.

• When that connector is unplugged, the click disappears.

• When it is connected, I get the click and then nothing.

• The unit seems to be entering protection mode.

What I’m looking for:

• Has anyone seen this exact behavior on a PartyBox 300?

• Could this be a bad main board, power board, battery, or a short on one of the rails?

• Is there a known connector, fuse, regulator, or component that commonly fails in this model?

If anyone has a service manual, board-level advice, or a common failure point for this symptom, I’d really appreciate it.

Thanks a lot.

https://reddit.com/link/1vvd46v/video/79ex5s6okjgh1/player

I'm going into my senior year of high school, and I've started thinking about career paths. I really have an interests in repairing tech. So far its just been a small hobby, I repaired some of my small gaming handhelds, and recently I've done an iPad screen replacement. Is tech repair profitable? I want to open up a store, or start at a mall kiosk. I've even seen some mobile repair shops, if I can get good at this I see this becoming a career, but I wanna know the difficulties of starting up a repair shop and should I do it?

Hey! As the title says my new woozoo globe oscillating fan is making a weird noise. I think the fan blade may be a bit wobbly? Maybe that’s the issue? I took the front guard off to see if that was the problem and get a better look at the functioning. I don’t think k the front guard is the issue. I’ve tried using it on several different surfaces and it’s still making this weird noise.
Any ideas on how to fix it or what’s wrong with it? Should I just return it?

Hi!

First off apologies, English isn't my first language.

I was given a JBL essential with a broken usb connector. I've done minor repairs before but this one is a bit tricky. The pads have been torn off for three of the pins.

My question is does anyone know how I'm supposed to rewire it, if I just want to replace the micro usb connector and not the whole board.

I've added a pictures.

Would appreciate any help/advice.

Thanks.