vmod simple help

[WeStSiDePLaYa]

im about to do this vmod on this page (first one listed). and im wondering why he needed to use GND for the capacitor?

was this needed? im planning on having it go 5V source => Choke => rubycon 1000uf 6.3v cap => mosfet leg.

is there a problem in doing this and having the volts go straight through the cap? id like to have the volts cleaned up a bit before feeding them to my ram.

also, would it be benificial to use 2 of the caps in parralel instead of one?

im planning to solder all of this stuff onto some old pcb that i will be cutting down.


http://forums.techpowerup.com/showthread.php?t=4751

[WeStSiDePLaYa]

Re: vmod simple help

here is what i made, its pretty poor soldering job i know.

5V+ source => Choke => 2x 1000uf 6.3v capacitors in parrallel => to MOSFET leg




seems the upload isnt working here. so look at this thread for photos.

http://xtremesystems.org/forums/show...92#post1332292

[kc8adu]

Re: vmod simple help

the cap is to ensure vdimm is clean.its - lead needs to go to a ground foil to do that.
it needs to be as close as possible to input of the vdimm regulator.

[Chris1992]

Re: vmod simple help

Oh yes, and Welcome to Badcaps Forums!!!!!

[WeStSiDePLaYa]

Re: vmod simple help

Would that not create a short circuit?

or do i connect the negative lead solely to ground, and then connect the positive lead to the source wire, and then the wire to the mosfet leg?

will the choke be much benefit to this?

looks like i will be creating another version. could anyone help me to put in some diodes or resistors to lower the volts about .7v? i just need a laymens diagram.

[davmax]

Re: vmod simple help

You certainly have an interesting challenge. Personally I would not attempt this.

Anyhow you asked about the choke. Well it is best left out because there are several issues. 1. the 5volt supply is basically DC with some ripple as is the 3.3Volt supply so there would be not much gain . 2. To insert a choke into a circuit with a heavy DC current can be rendered pointless if the DC current causes the choke to saturate, so the choke must be chosen to match the conditions of the circuit.

I have modified your pic. The negative connection to the capacitors must connect directly to the ground plane close to the MOSFET/transistor that is regulating the DIMM supply.

Diodes should be connected to the points shown so that the +5 volt supply passes through to the + side of the caps. The challenges are 1. Where to mount the diodes. 2. How many? 3. What current rating? 4. How to keep them cooled? The picture supplied with the mod instructions shows two dual diodes(4 diodes total) we have to presume that they are all connected in parallel. I cannot make a precise recommendation because the load current is unknown. If the current is 10 amps it would need to be shared between about 4 diodes particularly if there is vitually no heatsink to remove the heat generated.

Hope this helps.

[WeStSiDePLaYa]

Re: vmod simple help

i think im gonna make this easy on myself untill i get some better skills. and just do 2 caps in parrelel and thats it.

but now i have a question, do i have to worry at all about the current that this will be drawing? 2x512mb sticks have to be drawing a decent amount of current.

[Chris1992]

Re: vmod simple help

if you trust the PSU calculators out there, 10 watts per stick assuming ddr. thats 20 watts.

[WeStSiDePLaYa]

Re: vmod simple help

if you trust the PSU calculators out there, 10 watts per stick assuming ddr. thats 20 watts.

i dont think those calculators take into account 3.3v+ vdimm, and 260+ mhz. :

[Chris1992]

Re: vmod simple help

Watts are independent of voltage iirc, and with the OC maybe 15W/stick.

[WeStSiDePLaYa]

Re: vmod simple help

well, i finished the mod. and everything is working great so far. my vdimm is rock solid, i already can see it has improved oc at same vdimm as before, most likely the caps help there.

mosfets in the area seen about 25C increase in temps, but they still only peak around 50C, so they good to go.


ill get some pictures of the final project when i upload the pictures.