Sorry, you were right it Is the vbt/vtt thats dead, vref is working, switched wire, sorry..
Jep, vdimm is @ 2.9
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Sorry, you were right it Is the vbt/vtt thats dead, vref is working, switched wire, sorry..
Jep, vdimm is @ 2.9
If you want to replace the MOSFET with one of the same type, I think that someone over at OCforums managed to get one from the manufacturer (fairchild I think). It might be ok to just replace it with a general purpose MOSFET (eg IRF630) tho. I think that the chip might also have something to do with the Vdimm supply, but I've got the chip totally removed from my board, and it still works ok.
And then?
Made a vbt supllie with an opamp and mosfet? like you said?
I have no mosfets atm so it will be for monday or so, maybe I'll try tomorrow with some diodes from +3.3v...
Vref is 1.45v, vbt/vtt is dead, the two upper right pins of the burnt chip are vdimm, the 2 upper left ones are 0.3v, these 2 should be vbt/vtt..
With the death chip in place I measured 0v, now I removed it and measure 0.3v...
I just tried with a 470 ohm pot between vref and vbt, when I lower the resistance, vref drops quickly, I stopped @ 0.6v for vref, at that point, vref was vbt/vtt, both 0.6v, but this way I'll kill the vref supllie I think..
You could use an OPAMP, voltage divider and MOSFET to rebuild the Vbt supply. It would be good to try to get the board working using some diodes tho, so that you can check that it is just the Vbt supply that has died.
All the other voltages are fine...
Is your board also using a standalone vdimm supllie? Or only vbt/vtt..
How much amps does vdimm and vbt/vtt pull? So my mosfets are ably to handle the load..
But now my first concern is to know why the vbt/vtt died...
My other nf7-s has also the vref=vbt/vtt mod and is working for months 24/7 without any troubles...
on my board, I've got a Vdimm supply based around an OPAMP/MOSFET regulator fed from the 5v supply, giving 0-5v adjustable vdimm supply. I've also got the Vbt supply which follows Vdimm. The Vdimm MOSFET only gets slightly warm when I'm using 1*256mb BH-6 with 3.8v through it, but there is a fan/heatsink on the MOSFET. When I use my 1gb of TCCD with 2.6v in the board, the MOSFET and cabling to it gets VERY hot, even with a fan over the MOSFET sink, so its probably drawing about 10 to 15 amps. I'm using an IRF630 MOSFET for the vbt supply (which is more than adeqate), and an IRF640 MOSFET for the Vdimm (I would suggest using a higher rated MOSFET for the Vdimm, maybe a IRL2203N which is rated at about 80 amps at 100*c!)
Yeah 80 amps, thats the big stuff;)
I'll try to get to the shop tomorrow! I've a few broken psu's so I can sink the mosfets...
Then I'll buy the bigger version of the LM358 and make a nice vbt/vtt and vdimm supllie :toast:
Did you cut/removed the vdimm mosfets on your board?
Is there any kind of OCp or OVP on the board?
Btw, where did you connect the vdimm to you board? The vdimm cap? The mosfet or straight to the dimm's?
dubblepost
I removed the resistor that you solder to when you do the normal Vdimm mod, removed the 2 legs from the Vdimm MOSFET and connected the point that you normally solder to on the Vdimm mod to the gate (marked G on the PCB) via a 15 ohm resistor. This tricks the regulator into giving out whatever voltage you have set in the BIOS, but without it being connected to the RAM in any way. I don't know if you actually need to do this, but I did it incase you do.
I then connected the new Vdimm supply to where the other leg of the Vdimm MOSFET was. I left the Vdimm MOSFET in place on the board becasue it would have required too much heat to remove it.
I haven't found any problems with OVP or OCP on the board.
BTS240A
Is this also a possibility?
That should be ok.
Sweet,
I've a few out of car heating systems to control the electric fan speed, they're rated @ 58A continous and 200A pulse..
And, they're already attached to a big hs :banana:
So, back to the original post: have we come up with a mod that reduced the voltage drop under load? Someone want to sum it all up for us noobs?
Quote:
Originally Posted by Rub87
Unsolder the pot that's already on the booster, and connect the wires as shown in the picture, You can choose what potmeter you use, I'd say anything between 20k and 100k will work, then take an OPAMP, something like an LM358 for example, and connect the inverse imput to vdimm and the positive to the middel leg of your 20k-100k pot...
one side of the pot you connect to +5v the other to ground..
If someone can give me a hi res picture of the rear side of the booster then I'll mark the thing on it...
58A should be enough for RAM. The MOSFET I'm using is only rated to 16A iirc and it works ok (although it does get a bit hot!)Quote:
Originally Posted by Rub87
If someone can post some pictures of the front and back of the DDR booster, I'll write up a guide :)Quote:
Originally Posted by Stealth5325
The pot would need to be connected to the +5v supply, so that it gives a reference voltage at its wiper/middle pin of between 0-5v.
You're right, I was confusing with the "difference amplifier" (don't know the correct english name...
I'll delete the post, otherwise there will be more confusion..
wORKS LIKE A CHARM
Nice work! =)
Good to see it worked for you Rub87.
I finally got an OS onto my NF7-s yesterday to check how stable the Vdimm was under load, and I don't get any voltage fluctuaton read in MBM or on a DMM :slobber:. I need to get a scope to check what the voltage fluctution is really like tho.
I have a scope, I'll check it in the weekend... don't have time due school :mad:
Now I tried with the big BTS240A mosfet, prob is, when I connect the gate with the drain @ 12v, the voltage drop is 4v:/ Probaly I'll use the IRF640, but when trying @ 12v with a delta FFB80 the mosfet went verry warm after 5secs without hs so I think It'll be a little light for 1 gig BH-5 @ 3.5v
The BTS240A should have worked. I can't see anything in the datasheet to suggest why it wouldn't work. I've just got a small, low ariflow fan blowing over the MOSFET heatsink.
Did you connect both the gate and drain to +12v?
Jep, voltage drop is way to big to use it powered by +5V,
When powering the mosfet by +12V then it will work...
Now I tried it on my nf7, so only the vbt/vtt supllie, when I use 2*20K as voltage splitters and and LM358 it doesn't work when the OPAMP is powered by +5v, when powering the OPAMP with +12v and the mosfet (IRF640) with +5V its works great...
I'll fix tomorrow the Vdimm supllie, but I don't see why the OPAMP doesn't work when powered by +5V, then vbt/vtt output at the mosfet source only gets around 1.4v when the input voltage @ the non inv input is 1.65v... :confused:
The OPAMP needs to be connected to +12v so that it gives an output voltage of between 0-12v (actually it will be closer to 2-10v due to OPAMP limitations, but that doesn't really matter).
MOSFETs start to come into conduction when the gate pin is at about 2v, and about 10v will turn it fully on. With a 5v supply to the OPAMP is probably only able to supply a max of 3.5v onto the gate of the OPAMP, which is only enough to bring the MOSFET into partial conduction, which is why it works with a 12v supply to the MOSFET and not a 5v supply.
With the Vdimm set to 3.8v on my setup the OPAMP outputs about 7.5v onto the gate.