Leadtek PX 7300 GT coil blow?

[alindumitru46]

Hi,
In my absence, a computer at work succumbed and does not start because of a power failure (very often, in fact).
To locate the problems I used a good PSU (beQuiet 400W), to eliminate from the start the power problems.
All components have functioned less video card (!). At start, immediately heard a slight crack and got a thin thread of white smoke from the component framed in pictures.

Now I'd like to know exactly what component is, if I can replace, where I could find an equivalent piece, etc, in order to recover the video card.
Thank you.

[stj]

Re: Leadtek PX 7300 GT coil blow?

that's an inductor

[alindumitru46]

Re: Leadtek PX 7300 GT coil blow?

Ok, any chance to repair?

[momaka]

Re: Leadtek PX 7300 GT coil blow?

Ok, any chance to repair?

Yes.

The 1R0 on the inductor suggests 1 uH inductance. Also, it appears this inductor is connected to the 12V rail, which feeds the high side of the GPU and RAM VRMs. Given that GeForce 7300 and 7600 use very similar GPUs, they both have similar same maximum power requirements (most likely, the 7300 pulls a bit less). I know that a 7600 GT pulls around 50W max, so that means that this inductor on your card is probably rated for somewhere around 5-10 Amps.

By far the easiest way to get a replacement inductor is to get one from another broken motherboard or video card. It just has to say "1R0" on top and appear to be the same or bigger in size. SMD or through-hole is unimportant if you don't care how the repaired card looks .

And finally, if you can't find a replacement inductor, ONLY IN THIS SINGLE CASE, you can replace it with a solder bridge. Why? Because this inductor is connected to the 12V rail and is only used for reducing EMI and noise going back into the motherboard. (The other inductors on your video card are not, however, so do NOT ever try to replace those with a solder bridge - you will fry the GPU). If you do replace that inductor with a solder bridge, then I also highly recommend you install a cap in that empty cap spot marked "C7" (it's right next to that brown 16V 330uF KY cap). Use either a 16V or 25V cap. Capacitance can be anything between 220 uF and 1500 uF. The idea here is that if you remove the inductor and replace it with a solder bridge, then at least you'll have more capacitance to reduce some of that EMI noise from the GPU and RAM VRMs.

Let us know how it goes or if you have more questions.

**edit**
I forgot to mention - that white smoke you saw was likely from the label behind the inductor on the other side or the inductor itself. Either way, no need to worry. Now, if you saw smoke coming from a chip, that's a different story. But I have a feeling this video card will work just fine again .

[alindumitru46]

Re: Leadtek PX 7300 GT coil blow?

Aha, I really learned something new today ... the description is quite technical but very easy to assimilate.
I will try this weekend to look for a inductor, if not, I'll try the other method.
Thank you for advice.
I will come back with details along the way.

[alindumitru46]

Re: Leadtek PX 7300 GT coil blow?

Bad news... I replace the inductor with another with same value. But the vent start for 1 sec and stop only first boot.
I think is more damaged, not only this inductor is damaged but also another components.
I must test the mobo with another video card, because I think I damaged the PCI express port...

[momaka]

Re: Leadtek PX 7300 GT coil blow?

I must test the mobo with another video card, because I think I damaged the PCI express port...

Should be okay if the PSU detected the short-circuit and shut down. Otherwise, you will see either melted pins in the PCI-E connector or melted traces around it.

Bad news... I replace the inductor with another with same value. But the vent start for 1 sec and stop only first boot.

More than likely a shorted MOSFET. I had an AGP 7600 GS do that. Works fine after MOSFET replacement.

The short MOSFET is what probably blew/killed the original inductor on your board.
Check MOSFETS Q7, Q9, and Q14 for short-circuit (i.e. good continuity) between Source (S) and Drain (D), as well as Gate (G) and Drain. If they are okay, then check Q4, Q5, and Q10 for short-circuit between Gate and Drain only.

Q4, Q5, and Q10 are all "low-side"-type MOSFETs (i.e. they are connected between GPU/RAM power rail and ground. Therefore, they may appear to be shorted between Source and Drain while on the board, but actually be okay when removed. This will vary for different GPUs. If they show a short-circuit or less than 20 Ohms resistance, then the only way to know for sure is to remove them from the board.

To remove MOSFETs, you will need either two 60W (or greater) soldering irons OR hot air. I prefer the two irons method. It's very easy to remove the MOSFETs without damaging anything. Just apply a good amount of leaded (Pb) solder to all of their pins and tabs before trying to remove them. Also a good idea to write down the part number on the MOSFETs before removing them (in case they break). That way, you will know what replacement MOSFETs you need to get. The new MOSFETs need not be the exact same part number and specs... just compatible (I an help you find proper replacements if you choose to fix the video card.)

Or let me know if you have given up on it.

[alindumitru46]

Re: Leadtek PX 7300 GT coil blow?

Sir, I work in a field where theoretical and practical trainings are carried out both individually and collectively. But only few people manage to situations where "students" are totally overwhelmed .
I guess you are not alien to similar activity , beyond your good intentions .
I confidently implement your advice, even though I am an unknown in this area .

[alindumitru46]

Re: Leadtek PX 7300 GT coil blow?

Q4, Q5 Q7 are shorted, Q10 looks good. I found https://www.badcaps.net/forum/showth...t=12260&page=2 , probably I must do step by step replacements/verifications.
I found 3 replacement MOSFETs for Alpha and Omega Semiconductor D452 BE6L1Z (looks in photos) : http://www.digikey.com/short/t9tqj0 or a chinese kit of "genuine" from aliexpress.com
The best option, please?

PS: Do not give up , contrary: either the show or the hospital!

[momaka]

Re: Leadtek PX 7300 GT coil blow?

Q4, Q5 Q7 are shorted, Q10 looks good.

Q7 is bad!
It is an upper MOSFET, so if it shows short-circuit, it is very likely gone.

Q4 and Q5 must be tested again, but this time out of the video card.

Any of the three MOSFETs you posted should be okay, I think. The 497-13425-1-ND appears to have very close specs to the ones on your board. The IRLR8721TRPBFCT-ND seems to have better overall specs, though.

PS: Do not give up , contrary: either the show or the hospital!

Yes, now that's is the right attitude!

[alindumitru46]

Re: Leadtek PX 7300 GT coil blow?

Very difficult progress with this video card. I have started many projects, but fail to get used to peel off these chokes. An ordeal.
Meanwhile I managed to revive a chinese PSU: LC-350w and a motherboard.
I thought I post to help other users, but it is not something special.

[Dan81]

Re: Leadtek PX 7300 GT coil blow?

Very difficult progress with this video card. I have started many projects, but fail to get used to peel off these chokes. An ordeal.
Meanwhile I managed to revive a chinese PSU: LC-350w and a motherboard.
I thought I post to help other users, but it is not something special.

A LC-B350ATX is the PSU you repaired?

Man,those PSUs are like leaves - you find them everywhere!

I guess I'm pretty lucky I scored a 6600GT AGP,a Gigabyte GA-8IE2004 (w/Celeron 2.0GHz Northwood-128)and a Codegen 300X 300W (which is pretty beefy,although I have to replace one of the rectifiers (diode on bracket,for no reason considering a 200X 350W model I owned had rectifiers on all rails.) ). Out of these sadly,the 6600GT won't give any video. I recapped it using Rubycon ZL,Nichicon HM and UCC KZE - all 16v caps except for a 4v 510uF cap in one of the places. In case anybody asks - yes,I plugged the 4pin Molex cable for the GPU.

[alindumitru46]

Re: Leadtek PX 7300 GT coil blow?

You make me laugh . A PM was more appropriate.
I'm an stonecutter in front of you, guys from here

[alindumitru46]

Re: Leadtek PX 7300 GT coil blow?

Yes! Yes of course, man! Of course it did, thanks in particular to @momaka!
I try for half an hour to post, just now I did.

[momaka]

Re: Leadtek PX 7300 GT coil blow?

So does it work now? Can we see some pictures?

[alindumitru46]

Re: Leadtek PX 7300 GT coil blow?

The single mosfet replaced is Q7, even if Q4 and Q5 had the same reaction to measurement like Q7. Is there a risk?
I dont have a good skill and my iron has only 60W, so this is my dirty job. Already has 4 days and 4-5 hours of daily running. I found a little high temp on the mosfets and the other side (slightly hot sensation when touch, so under 60 Celsius degrees).

Saturday night I mannaged to power up a mobo Intel G845GSVR with 5 capacitors 830uF-6.3V blowed beside socket. Altough I finnished repairing
3 weeks ago, I must reset the BIOS pulling up the battery for 1 week and using an old CPU.
So a double win in the week end .

[ChaosLegionnaire]

Re: Leadtek PX 7300 GT coil blow?

just put heatsinks on the mosfets if u're concerned and want the card to last a long time. for me, whenever i see a bunch of mosfets clustered together like on your video card, i have an insatiable itch/urge to stick mosfet heatsinks on them.

i like doing that becuz cooling the mosfets actually improves their switching efficiency so less electricity/energy wasted as heat. it also saves money in your power bill. mosfet heatsinks are dirt cheap so its a cheap and easy way to save money in your electricity bill.

[alindumitru46]

Re: Leadtek PX 7300 GT coil blow?

I think you're joking when talking about electricity savings . This videocard consume max 20-30W , how much to save, 10%? 2-3W ?!
By sheer coincidence, I have some DDR2 radiators, but these MOSFETs have ~5mm x 5mm (0.25cm square surface). Too difficult to complicate things.

Max operating temperature of 60 degrees seems ok, I do not see anything dangerous in the datasheet. By the way, the fan blow air trough radiator blades to memory chips and mosfets.
If u think temp around 60 Celsius degrees are dangerous, tell me.

[momaka]

Re: Leadtek PX 7300 GT coil blow?

Well, congratulations on the fix!
Looks really good, too. Especially when considering you only used a 60W iron.

The single mosfet replaced is Q7, even if Q4 and Q5 had the same reaction to measurement like Q7. Is there a risk?

No risk.
As I mentioned, MOSFETs Q4 and Q5 are used on the "low" side of the buck converter, so they will appear shorted because of the GPU chip. That doesn't mean that they are, though. MOSFET Q7, on the other hard, should *never* show a short-circuit on the board. That's how I spotted it was bad as soon as you gave me your measurements.

So leave MOSFETs Q4 and Q5 in there "as is".

Already has 4 days and 4-5 hours of daily running. I found a little high temp on the mosfets and the other side (slightly hot sensation when touch, so under 60 Celsius degrees).

That's normal these days.
If it doesn't burn your finger, it will work fine.
However, I would *strongly* advise (again) to add those missing caps in the empty cap spots (spots C7, C28, C47, and C34).

C7 is right next to that brown 16V 330uF KY cap. You can use either a 16V or 25V cap, with capacitance rating anywhere between 220 uF and 1500 uF.
For C28, C47, and C34 I think a 6.3V-rated cap with capacitance of 470 uF and up would be good. You can probably also use a 4V polymer.

Finally, check what GPU-Z gives you for this video card in terms of core and RAM speeds (and maybe even post a screenshot if you like). Reason I mention this is because your card has Samsung K4J55323QG RAM chips, which are capable of running at 400 MHz (800 MHz DDR speed). Meanwhile, that 7300 core should be capable of 400-500 MHz.

for me, whenever i see a bunch of mosfets clustered together like on your video card, i have an insatiable itch/urge to stick mosfet heatsinks on them.

I am usually too lazy for that. I don't do it unless the MOSFETs really do run very very hot. And if it's TO-252 or TO-263 MOSFETs, I prefer to solder thick solid wires to their drains and have the wires stick up in the air. Much better heat transfer than heatsinks that are in contact with the case (the black epoxy case is not a very good thermal conductor).

[alindumitru46]

Re: Leadtek PX 7300 GT coil blow?

If it doesn't burn your finger, it will work fine.
However, I would *strongly* advise (again) to add those missing caps in the empty cap spots (spots C7, C28, C47, and C34).

C7 is right next to that brown 16V 330uF KY cap. You can use either a 16V or 25V cap, with capacitance rating anywhere between 220 uF and 1500 uF.
For C28, C47, and C34 I think a 6.3V-rated cap with capacitance of 470 uF and up would be good. You can probably also use a 4V polymer.

Finally, check what GPU-Z gives you for this video card in terms of core and RAM speeds (and maybe even post a screenshot if you like). Reason I mention this is because your card has Samsung K4J55323QG RAM chips, which are capable of running at 400 MHz (800 MHz DDR speed). Meanwhile, that 7300 core should be capable of 400-500 MHz.

Yes , Sir!
I know about Samsung. Yesterday, while writing the post on badcaps.net, I run FurMark and Afterburner. I reached 520MHz (420default) with a maximum of 64 Celsius on the GPU and the Ram went up in 800MHz (default 700), both with 10MHz increments. After half an hour, at 800MHz on the memory already bored me. I may try another time.
I think can be marked as resolved /closed.
Now I'm ready for something more complicated.

Thank you very much, again.