Got a no-name ATX 600watt PS which is dead. Won't power up at all.
No obvious bulging caps etc, but the two large ones are odd.
Claim to be 680uF 200v 85C, but both measure at 200uF with an ESR of 0.17 on my component tester.
Thinking that strange checked the capacity using my Fluke, and that too said 200 uF.
Anyone seen anything like this?
En el artículo , Dave Plowman (News) escribió:
You're testing them in-circuit, so results are going to be meaningless.
Is the mains fuse blown? If it's completely blackened, I'd suspect the bridge rectifier or the chopper transistor, especially with the out-of- kilter readings you're getting from the mains reservoir caps.
No I'm not. Give me some credit.
No.
En el artículo , Dave Plowman (News) escribió:
What make are they? May be one of the usual culprits (Teapo, CapXon, Rulycon (sic), Luxon, etc.) that make crappy or fake product.
It's very unusual for mains reservoir caps to go wrong, usually it's the ones on the output side. That's why I suggested you may be testing in- circuit.
Time to start probing voltages on the primary side then, starting by seeing if there's about 350V dc on the reservoir. There should be a bleed resistor to dissipate any charge on these caps but it's not always present or functional on cheap s**te PSUs and be aware, those caps really can bite (I know you know this, it's for the benefit of anyone else reading.)
If it is truly is completely dead (not even trying to start - no ticking sounds, etc.) could be something as simple as a faulty switch or a dry joint where the mains load from the switch connects to the board or on the bridge.
If all that looks ok, trace the startup feed to the PWM IC that controls the chopper transistor. That is usually a high value resistor from one side of the rectified supply that can go open. There will be am associated zener to limit the voltage, check that's not shorted.
Not uncommon, but low capacitance doesn't normally prevent the PSU starting up - it just knocks its effective power rating down considerably (might fail if the load is high). High ESR would be a more serious problem. (If it's a wide input voltage rating without a selection switch, then the high capacitance is only required when operating at the low end of the range anyway.)
The capacitor which stops it from starting up is a small low voltage one on the hot side which smooths the DC supply for the oscillator and control circuit.
Obviously, other things like blown FETs are a possibility too (usually take the fuse with them, and sometimes the bridge rectifier).
Not going to spend much time on this since it's my brother's PC. Sent it down here as his local place said it would cost more to fix than it was worth.
It's working fine on a spare PS here - but would like to fit a new one. Any recommendations as to which make to buy for best value? And where from?
I've been very impressed with the Corsair CX430M PSU which I bought to replace the unbranded one which was supplied with my PC and which failed during a thunderstorm despite a surge protector. It has a very large slow-revving fan (rather than a smaller, faster-revving one) which means there's less fan noise.
If it's an old PC I'd just take a moment to check the PSU leads will fit the motherboard etc.
I was going to suggest this. I have had 6 of them running 24/7 for over year! They are a bit more pricey, and the OP mentioned 'value'. They are good value but slightly more than the average in price. Get the CX430 if not bothered about the modular cable setup, although there is little difference in price.
They are quiet, and they are 80+ Bronze rated so he may save a bit in electricity to make up for the slightly higher cost!
The CX430M has a 20/24 single plug, also an 8/4 pin CPU connector. The other cables are both SATA and the old 4 pin Molex. And the 'floppy' connector.
Not that old. All the drives are SATA.
The only criticism I have of the Corsair is that the power connectors on the SATA lead for hard disks are rather close together so won't power two devices unless they are very close together in the case. Of course this can be solved by buying an extension male-female lead. Two of my HDDs are fitted side by side in the case, rather than the more usual one under the other, and this means that there needs to be more separation between one power connector and the other on the same lead.
I never had that problem - they're all Corsair cases!
This is a Dell PC. It has a column of 5 1/4 and 3 1/2 bays for DVD drivers and HDD devices (one of the 3 1/2 bays is taken up with an SD/CF card reader). Those are fine. But when I came to add two more 1 TB drives, the only spare bays were down the bottom of the case, alongside each other. I suppose I could have got a 5 1/4 to 3 1/2 adaptor and put one of the drives in the unused second DVD bay. Might do that as I'm thinking of adding another drive to move my music and photos off the system drive which is getting a bit full.
The cables are plenty long enough to reach from the PSU to the bottom of the case (a bit *too* long - all that cable is an embarrassment!) but it's a tight stretch from one drive to the other.
But a great PSU apart from that minor niggle.
Cheers
Spoke to soon. With the replacement PS I had lying around 350w rather than the faulty one which was 600w, it did fire up.
Some time later decided to check it out properly with all the peripherals connected. And it wouldn't power up. Only difference was the LED on the motherboard was on meaning it was getting the standby supply, unlike with the broken one.
So it looks like a motherboard fault which may have been the cause of the original PS failing?
Disconnected everything I could - HDs, DVD and video card, but still wouldn't power up. Obviously, checked the switch.
It's an Asus MB. Have had one of those fail before.
In article , Dave Plowman (News) scribeth thus
Quite possibly bu^^ered caps on the motherboard, but if its a few years old then in all not worth repairing as much as we may like to renovate something but no circuits or service info will be around;(.
That is of course that the MB is OK with its new power supply, some connections are/may be a shade different...
Not really. Very few variations with ATX supplies.
The processor is an AMD 3500+ 2.21G type, so not exactly new.
Not sure If I should go for a new board and processor, or look for a used one on Ebay.
I did exactly the same. I finally took the advice, that more knowledgeable people than I, have been giving me for years while I knocked-up my self builds.
I finally made the change when hard drives, one only a week old, went dead. Totally! A lot of searching brought home the fact that the PSU is capable of producing all the problems I was having over that year.
So, I too went for a Corsair after being advised that it was cheaper than the named one I asked for; that it was of equal build and, it carried a longer guarantee. The difference in performance was obvious from the start. And, no heat worth mentioning from the area of the PS.
I won't 'afford' buying a no-namer' again.
...Ray.
Wow! How the hell do they get away with that?
...Ray.
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