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  #21 (permalink)  
Old November 8, 2013, 03:09 PM
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Vishay - MOSFETs - N-channel - DPAK (TO-252) package

http://www.onsemi.com/pub_link/Colla...TD15N06V-D.PDF
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  #22 (permalink)  
Old November 9, 2013, 02:18 AM
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Oh, man, that one suxx bad:
Semiconductor MTD15N06V
http://www.onsemi.com/pub_link/Colla...TD15N06V-D.PDF
60V, 80mOhms, 15A, rise time 51uS, shutoff time 18nS
gate charge 14.4nC, gate treshold 2.7V!

60V is too high (unnecessary, source is 3.3V, output 1.5V), 15A is not much, but 80mOhms is notably worser that the 50mOhms it is there AND more resistance when current flow = more heat! And we did not like heat, did we? Also the rise time is 8.5x slower that with the original mosfet (6nS only!), while the shutdown is rougly same.
But with same gate charge is there a huge problem (hence the 60V unnecessarity) with the gate treshold. That is very very high 2.7V, while the original works at 1.2V. Therefore this mosfet probably will never even work in the mainboard... :(

...but from this very interesting link you posted:
Vishay - MOSFETs - N-channel - DPAK (TO-252) package
...I choose this one:

Vishay SUD50N02-06P
http://www.vishay.com/docs/71931/sud50n02.pdf
20V, 6mOhms, 26A, rise time 10nS, shutoff time 24nS
gate treshold 0.8V, gate charge 19nC


Even that at 4.5V the resistance is actually 9.5mOhms, then it is still far better that 50mOhms.
Also the mosfet can operate at 175C, witch is pretty high.
While it is a bit slower (rise time 10 to 6, shut off time 24 do 20), the gate treshold 0.8V should compensate that a bit for the original is 1.2V... The slightly higher gate charge 19nC over 15nC should not be a problem.

I believe I found the perfect replacement, that is better than the original!
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Last edited by trodas; November 9, 2013 at 07:29 AM.
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  #23 (permalink)  
Old November 9, 2013, 06:52 AM
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Trodas I just threw it out there to let you search

a fast unit problem is the package TDFN
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Old November 9, 2013, 07:38 AM
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Och, that... I did not quite got it. I was under the impression that you choosen this one - lol. That would be a pretty bad, maybe even fatal choice. But the link to the Vishhay table was priceless, as there are MANY very good and interesting mosfets. And the Vishay SUD50N02-06P seems to be the best choice with almost identical the critical parameters, while with better resistance it will generate less heat and in general, have a higher reserve of possible delivered power.

Quote:
a fast unit problem is the package TDFN
Interesting controler, but I have no idea, where you are going by this way? So far, the mosfet controller are fine, the regulation works and what I set in bios, that voltage get out to the AGP...? It is not stable when the card go into 3D mode (or even AGP mode) and start to draw more power, but that is the reason I blame the capacitor there for being unsupportive to the voltage regulation...
No idea what your point should be.

The only inderesting thing was this from the PDF:
Quote:
the minimum power dissipation occurs where the resistive losses equal the switching losses. Choose a low-side MOSFET that has the lowest possible on-resistance
...and that is exactly what I do. 50mOhms is horrible, 6mOhms sounds much better, altrought at given voltage it will be close to 12 or 14mOhms (20V = 6mOhms, 4.5V = 9.5mOhms, 3.3V = 12, maybe 14mOhms?), it still will be tad better that what I use currently. So if the capacitor exchage did not help (there is IMHO not big chance that this won't help, as the mobo was used to run at AGP 4x with weaker Radeon R9100 card, so no reason that this should not be the cap issue), then next is the mosfet exchange :)
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Old November 14, 2013, 06:48 AM
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I managed to replace the last remaining capacitor on the MSI PM8M3-V mobo - the 10uF d4 SMD suxxka, that have kinda horrible ESR or 3.2 Ohms:



...with a new SMD tantal-polymer KEMET 220uF 2.5V capacitor T520B227M2R5ATE015

...with have ESR around 0.015 Ohms :D

That should be a huge improve. Also I, out of the desperation, resoldered a bit the drain tops of there NIKOS mosfets near the AGP slot.

And result?

ABSOLUTELY NONE!

So it looks like that the mainboard was not up to the blame the whole damn time. It is the videocard that have to be recapped.


The Radeon R9100 was crashing when new SoF2 level is loading. Given that it run passively cooled on Licon caps:



...with 60 mOhms ESR one should not wonder. Rest of the caps looks quite similar, so recapping is in order, just waiting for the caps (as usual).


The PNY 6800 GT failed after a short time to run in AGP mode, going down to PCI mode and crashing after some gaming is played. Now that is serious problem, because there are just THERE caps, two of them polymers on the voltage input filter and they are Chemicon polymers.
Last one is unknown 100uF SMD cap and that it is for other that ceramic caps! I would be inclined to add some caps in the blank spots too, probably something over 100uF SMD... and I would also like to create a custom effecient heatsink for the mosfets on the card, because they do overheat a lot - GPU VRM temp 71C: View image: temperatures after 30min


Should I try recap these graphic cards before I try replacing the NIKOS mosfets? :confused:
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Old November 19, 2013, 02:52 AM
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Quick report - after recapping the Radeon R9100, I put it into my MSI PM8M3-V mobo and at first it show ram errors (heartbreaking, after so much work and so many polymers and added caps...) on the screen, so I have to pull it off and check.
Fortunately, I managed to find the bit of tin, that ended up on one of the bottom ram chips and after cleaning - hoooray, all works like a charm!

Immediatelly the card go into AGP 4x mode (!) and despite being TAD slower that PNY 6800GT, the system feels notably faster. That is, because, PCI mode DO SUXX BADLY. Therefore it is getting almost sure that the mainboard was NOT for the blame. The bad caps are in the GFX card(s), witch I indent to fix, of course.

Now is time for a clean win install and then I do more testing - mainly the play testing and longetivity under serious load. Then I might be inclined to see, if I can overclock the card a bit, despite the poor speed to start with :)

The lesson from all this is too early to draw, but there are only 3 caps on the PNY 6800GT, that are not ceramic: two Chemicon polymers 330uF 16V d10 SMD and one 100uF 16V d6.3 SMD Nichicon UD with 3.4V on it + some empty spaces, but that it is.

Since I was getting about 71C on the VRM mosfets ( View image: temperatures after 30min ) with just the ATI tool cube in small window, then I suspect these Chemicon polymer caps are up to the blame.

Of course the cooling of these mosfets is poor, but that was unchanged since day one and the card worked well for me before, so...
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  #27 (permalink)  
Old December 2, 2013, 11:24 AM
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Today is the day! :) UPS delivered a 10pcs of Vishay SUD50N02-09P-E3 mosfets samples from German Vishay HQ. Hoooray!

Therefore I immediatelly went to work. First at all, there is a picture that show the "polymerization" of caps near the AGP on the MSI PM8M3-V mobo:



The remaining two non-polymer caps (Nichicon HM & Samxon GC) run at 5V, so there is no good substitute for them, but for the rest, the capacity was bumped (2x 1200 & 2x 2200uF) as well as the specs.

The yellow KEMET tantal-polymer 220uF 2.5V cap is also well visible, as replacement for the 10uF 16V SMD suxxka cap :)

However that did not helped, so it is a time to replace the NIKOS P3055LDG mosfets. I picked (for the start), the two, that are most suspicious: the two most close to the AGP slot - the left one delivering the 1.50V and the right one 2.50V to the AGP.
(as you remember, lowering the 1.50V voltage from default 1.55V helped considerably with stability, so it is not like I picking up on random mosfets)

Sadly, the place is pretty crowded, so I had to pull the caps off first:



And as you can see, there are new Vishay SUD50N02-09P-E3 mosfets soldered in! I did not skip on the tin, as you can see, trying to lower every possible mOhms out... :)

And then I soldered back and... tried the mobo. Worked right away, hooray! (with Riva TNT) Then I tried with my R9100 and it also worked well, so I pulled the machine together and now I typing on it, as you can see :D

But first news is bad news. There is no instant "back to AGP mode" in Win. Still it show PCI mode, so I probably have to reinstall the graphic card to get again AGP mode back, as I always had it, before the crash during gaming...
So no instant fix.

But since it crashed by playing in PCI mode too, then I first try playing, so I can determine the stability. If anyone can cross a finger or two (or even say prayer, tough I cannot believe in anything these days), it might help ;)

Mosfets choices:
Replacement for NIKOS P3055LDG mosfet? - Badcaps Forums
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  #28 (permalink)  
Old December 2, 2013, 11:37 AM
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good job Pavel,

agp thing is bios coding for its looking at old settings to turn on agp
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  #29 (permalink)  
Old December 2, 2013, 01:52 PM
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Thank you! Bios was reseted (in fact, despite my repairs and new battery, this mainboard lose bios settings and time every time it is pulled off the electricity for longer that 2 min or so), yet like as I write, it will need reinstall. Again. Sigh.

But I have a backup before GFX card install, so it should be much easier now :)

However at the cursed PCI mode, I did played for 2h 30min... and... no crash.
I did not want to claim something, but... it does not crashed and I can even do printscreens! (never been able to do this before for a loooong time)

So, maybe this will be a good start.

I would like to mention one more thing. The desoldering, the left mosfet (the 1.50V one) gate did crash up, opening the package a bit when desoldering. It might be, that I was too harsh on the poor old Nikos mosfet, but... I do the same with the previous one and the legs stays and nothing cracks.
To me it looked like a structural failure... but I could be wrong. Yet if I'm right, then it would explain easily the crashing problem - once heat up, problems become... Let's see, if this will be stable, finally. I got tired and a bit having a headache from all the gaming now, so... Enough for today! :D

Vishay mosfets - yea! 175C max. working temperature - that is ownage! :)
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  #30 (permalink)  
Old December 6, 2013, 02:07 AM
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And it worked stable, till I decided to tickle it a bit with overclocking of the R9100... :(

The overclock was not that bad:



It can do 293 for the GPU, but I backed it down to around 290, same for the rams, around 248MHz it can do. That make it clear, why these rams had to run at 200MHz, because they cannot take the normal 250MHz reference design clock, not with any caps.
Hence I cannot match the XT version (300/300 vs 290/248), but at lest some overclocking is possible. It would be interesting to know, if adding more caps on the empty spaces (there is space for DAMN much caps!) could help to reach faster speeds. I was kinda hoped for the 300MHz mark, but I got burned shy 7MHz of it...

However I have saved previous max. stable O/C results and they are:
250/200 - to 265/248 ;)
Now it is:
250/200 - to 290/248 ;)

So nothing can help the rams, but the GPU is overclockable better with better caps. Yet the main catch is, that the board started to crash and hang after post again :( Therefore I did not managed to fix it yet :(
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