Hello...

My sister purchased an M2 MacBook Air a year and a half ago. While she was using it a week ago, it randomly shut off and no longer powers on. There are no signs of life and not even the MagSafe indicator LED lights up.

We took it to Apple and they disconnected the battery and tried a bunch of stuff before they declared the logic board "brain dead" and quoted us about £567 to replace it. Typical of them...

eBay replacements run about £367 with the Touch ID sensor included.

I did consider to probe the logic board for shorts...

Hello...

I've got my old Lenovo G780. It had a broken screen a while back and I replaced it with an aftermarket one. The aftermarket one died after a year (shocker) and some really strong plastic smell started coming from the laptop. When I went to open it up, I found a burned mosfet in what the schematics call the LCD Power Circuit, which I assume is the inverter?

I'm not sure if I'm supposed to link schematics but they're easy to find. The mosfet's label on the motherboard is Q80 with a part number of PMV65XP.

They seem to be on eBay. Should I just...

Re: Corroded GA-B85-HD3

Hi, thanks for the reply.

The problem is... I don't have an ultrasonic cleaner. I'm just a humble hobbyist with a soldering iron and a SS-02 pump

Since I wasn't getting replies, I tried cleaning the corrosion with some vinegar, then soapy water to rinse it all off, and then IPA. The board is much cleaner now but no dice.

In fact, it has stopped posting (before I did the cleaning, which is why I rushed it) and all it does is power cycle itself. The fans will spin for two seconds, then they will spin down, and...

Hi all...

I have a Gigabyte GA-B85-HD3. It mostly works but it has a few problems. At random times through the day, I get constant notifications from Realtek's Audio Panel that the rear jack has been connected/disconnected. It spams me for a few minutes and then stops.

Second weird issue is the integrated graphics have red artifacts. I've seen those in boards with bad caps, so I concluded that the caps must be bad... especially because the board has signs of corrosion everywhere.

But upon closer inspection, this appears to be environmental corrosion...

Re: ASUS P5KPL-AM.I bought caps with a big tolerance rate

Well it took hours to clean all that "stiff" solder but I eventually managed to do it with my Engineer SS-02 pump. I did damage one pad but the rest are OK. In hindsight, a hot air gun might have been best for this. I had to re-tin the pads to try and get old solder way too many times. But I don't got one of those.

Anyway, it works now, and no more weird behaviour. This was my first re-cap so I honestly wasn't sure it would turn on again

Re: ASUS P5KPL-AM.I bought caps with a big tolerance rate

Oh, yeah, I removed some of the old caps today and their capacitance had degraded to 640uf with an ESR of 4ohms. I'm surprised this thing was still functional.

That said, there is a bit of a problem, the solder in that board is very stiff and I can't suck it away easily. Even when I do, there are bits of it left within the holes and that prevents me from putting the new ones in. I tried reflowing it with fresh solder and flux but it isn't working hmm...

I can usually desolder no problem but sometimes...

Hello,

I have an ASUS P5KPL-AM board with swollen and leaky capacitors. Amazingly, it still works, but I'm guessing it won't be long before it doesn't so I'm looking to replace the capacitors. All that electrolyte is probably not good for the traces too.

Anyway. Every cap on that board that is 820uf 6.3v is swollen, so that issue is isolated to those specific caps. They're TK AWTY caps. Never heard of them but I suppose they're bad quality.

To replace them, I bought Rubycon ZLH capacitors with the exact same 820uf 6.3v spec. But when I went to test...

Re: Old Compaq Armada internal PSU repair

Well, okay, I'll have to order more parts. I'll post back when I get around to building the PWM prototype.

Re: Old Compaq Armada internal PSU repair

So you're saying that I should get a UC3843 and wire it up in a prototype board with the basic configuration the datasheet has. Ok, I can do that, I've made prototype boards before for a Raspberry Pi Modem Project.

But uh, this is the part I don't get quite understand:

"Lift the gate pin of the power MOSFET and the two primary side pins of the optoisolator off the board and also connect these to your board. The source pin and current limiting does not really matter for now - use the series lightbulb trick...

Re: Old Compaq Armada internal PSU repair

Huh, you were right! The voltage in the startup cap stays at a constant 11.3 volts. But that also seems low. It's a 32v capacitor, why would they use something this high for 11k volts?

But I also noticed that upon disconnecting the PSU from the wall, that voltage starts to fluctuate between 11.3 volts and 9 volts before it settles at 9 volts.

Weird... I'll have to look for that resistor you talked about.

It looks like this PSU is toast though if the PWM controller is dead. I don't think those black-coated...

Re: Old Compaq Armada internal PSU repair



Yeah I'm guessing the PWM controller is inside those black-coated PCBs, in which case, I'd have no idea what chip to replace it with. If its the PWM controller, I'm guessing its impossible to revive that PSU.

I'll do those measurements today and tell ya, have to re-assemble the PSU though....

Re: Old Compaq Armada internal PSU repair



I think its the main voltage cap? Is that what its called? I always see these super big capacitors in old supplies like this one. Its at the primary side so I'm guessing it acts as a buffer.


Its another KMG rated for 400v 65uf. I'd say it works because every-time I discharge it, it makes a pretty big bang. Like a firecracker! But I also measured the voltage across it when the PSU is on, there are 350v there which explains the bang :P

Its not the only high voltage cap though, there is a black...

Re: Old Compaq Armada internal PSU repair

Good morning!



I went ahead and did more testing today. The disc cap was hard to pull out because it was behind the transistor, so I had to take this out as well. When I did, I discovered that this was actually the coil, and this was actually what had the short across it, not the ceramic cap the ceramic cap is fine.

Here are some markings to help you out:

Blue --- Transistor (by the output caps, which is the secondary side I think)
Red --- Coil windings connector 1
Light-blue...

Re: Old Compaq Armada internal PSU repair

Yes, I checked the zener diodes on the secondary side --- all good!

There are two diodes besides the output caps (should have mentioned) a regular black one and a zenner one at the edge of the board. No short on the zenner, but a short at the black diode. It's not the diode causing the short tho, its something else.

I did check the transistor besides the output caps with the multimeter. Don't those fail shorting the gate to one of the pins? Anyway, the short isn't coming from there because the Gate and Source pins...

Re: Old Compaq Armada internal PSU repair

Found a short at the diode besides the output caps

But even after removing it to double check, the short is still there. And the diode itself forward biases fine once I removed it, so its not the diode causing the short... its something else.

There is a tiny SMD diode underneath the PCB (D7) where the output caps are. But I'm not sure how to test that.

Re: Old Compaq Armada internal PSU repair

Definitely not. It might be the camera making it look that way but the colour looks pretty consistent IRL. I don't see any burns, BTW There's two of them...

Re: Old Compaq Armada internal PSU repair

My camera sucks and it really can't focus up any closer than this, but here are some photos from different angles.









That M-Tester I have can test all kinds of things, let me know what you want to test and I'll take it out!...

Re: Old Compaq Armada internal PSU repair

Well, I replaced the startup capacitor today — still nothing.

I also checked the voltage across the big brown cap next to the startup cap and the voltage was 350v. Makes a pretty impressive bang when you discharge it too. Something is telling that this isn't the problem...

Re: Old Compaq Armada internal PSU repair



Oh, crap. Even though I've been messing with retro tech for years this completely skipped my mind. God...

I've never bought from Aliexpress but they are cheap as hell, almost alarmingly cheap. They seem to guarantee that I'll get my items within 15 days if I buy over £9 of things.

My problem with CF is that the adapter is cheap, but the CF cards themselves are expensive as balls. £15 for 4GB of memory? You can get a 32GB SD card for £5...

Also, I did some research, and apparently...

Re: Old Compaq Armada internal PSU repair

Well, for now, I will wait for the capacitor

Meanwhile, I realized that I don't have a hard disk to install an operating system into when I do get this thing booting.

I'm aware of SD card adapters but laptops use 2.5 inch IDE and not the normal size one, so I'd have to get both 2.5inch adapter and an SD card to IDE adapter. Which starts to make things really pricey...

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