Voltage Mod Adjustment Circuit

[Skitzo]

sweet

hey now that's looking more like what I want. I will have to read up some more but it sounds almost perfect. Will have to find out how it works. 64 steps with two wire up/down interface so a tac switch should work for triggering. It wonder what step it starts at when it is initially powered? If it would start at the first(no extra voltage supplied), there would be no need for standby power to remember the last state before power down. So far I only see one down fall, I haven't worked with surface mount yet. I guess I'm gonna start making my own printed circuits. Are there prototype boards for surface mount applications, I only ask because I haven't seen any yet.

Thanks alot Fr@nk

 

[Skitzo]

hrmn

I just took a pic of my card and noticed some burn marks. If some versions of this card have been altered to omit the 6 pin connector, perhaps other components have been down graded aswell, not sure.

All I had to do was think of doing a volt mod and I burnt my card lol

this card has only experienced oc'ing via riva tuner...

the resistors were marked for my confirmation
this is not to instruct where to do the mod

 

[largon]

Skitzo,
I still don't understand why you think this unnecessarily complicated circuit would be more practical than using just the conventional trimmers (VR). I see you've often said that your method would allow voltage tuning while the system is running. I don't know why you think trimmers can't be tuned while the card's powered - that makes no sense. There are no "adverse effects" whatsoever. Actually, trimmers should only be tuned while the card is running. This way you can (or more likely you should) continuously measure the supply voltage (vOUT) when you tune. Tuning a trimmer on an unpowered card is never recommended (unless you know exactly what you're doing - which most users don't).

Pencil modding on the other hand... Well, in my opinion pencil modding is such a half-assed method of vmodding that I personally do not ever recommend it. Pencilling SMDs (especially the FB resistors) on a video card while the card is powered is pure insanity; while the markings the pencil leaves behind has very high resistance (~30kΩ) the actual tip of the pencil is a very good conductor (~15Ω). Basically the tip will shortcircuit anything it touches. If the tip or even the pencil shavings were to short the resistor you can kiss your card goodbye as shortcircuiting the FB resistor will cause the phase controller to "open the floodgates" in the PWM resulting in vOUT (vGPU, vMEM, w/e) to jump to ~maximum the mosfets can output. Usually that's ~12V.

the main focus would be giving the card the optional extra power from a safe source

That's simple: find the 12V-source plane of the vGPU mosfets using a multimeter (= DMM). Find 3 such spots from around the mosfets and solder wires on them with connectors that fit in a PCIe 6pin plug or a molex of your PSU. Then solder 3 wires from any ground (the closer to GPU chip the better) with similar connectors. Plug them in and you're done.

with the ability to make adjustments (or disable the mod) while the computer is running.

Trimmer allows exactly that. Quickly disabling the mod can be done just as easily via either:

Jumper:

This VR+jumper combo is used on my 8800GTS atm.

OR

Dip switch:

Here one dip controls two trimmers. (parts are not soldered together yet)

All in all, this "vmod controller" is unneccesarily complex and it does not offer any gains compared to trimmers.



Btw, about the pics of your card - I don't think those are burn marks.
They clearly go beyond different power planes so they must've come from outside.

PS.
What is this "tac switch" you're talking about?

 

[Skitzo]

...

Thanks Largon;

I'd have to agree with you about the pencil mod. It has been know to get results, but not in a manor I find acceptable. I was under the impression, from everything I've read, that adjusting the trim pots while the card is operating was not safe. You are the first to mention otherwise that I have come by. It makes more sense to do it with the circuit live. Although, isn't it also possible to adjustment the trimpot (unpowered) with a mm assuming you know the resistance level you want. I really need to spend alot of time exploring avaliable parts, the trimpots I've seen were alot larger. The tac buttons, http://www.ace4parts.com/Products/T...A--at-12VDC--(On)-Off---(2)-pk__30-14411.aspx , are a way of having the adjustments made accessable from outside the case. They look a little nicer than the trimpots I've come across, so would be a little more presentable in my opinion. What do you think of the digital variable resistor listed by Fr@ank? Could it not function like the circuit I've suggested.(much simpler though). Wouldn't it be possible to replace the indicated resistors with something like this? (used either as a second path or the main path) I like the idea of stepping because it seems like it may prevent raising the voltage too fast(is there such a thing in this case?).

Your trimppot/dipswitch setup loks quite nice though...two little holes for adjusmnt,another for the dip.

 

[largon]

Those VRs in my pics are infact quite large in size. They measure 19mm x 5mm x 6mm (L x W x H). The smaller ones I have are 7mm x 6mm x 4mm. You've probably seen "high-wattage" pots like the one here that feature hundreds of times the wattage that is needed for vmodding purposes.

Digital VRs should work too but when you include the controller, switch, etc. the physical size of the whole circuit will be big enough to necessitate you mount the parts on a proto-PCB. It wont be pretty.

it seems like it may prevent raising the voltage too fast(is there such a thing in this case?).

The steps aren't necessary - you could go from 1.1v to 1.5v in one step and the card would be none-the-wiser of what has happened...

 

[Skitzo]

Good show Largon

Thanks a million Largon. I gotta tell you, so far Largon Electronics 121 has been great! I'm not adverse to finding things on my own, but sometimes a fellow needs to be pointed in the correct direction. I get information from as many sources as I can, but it can often be missleading. Too bad the internet doesn't have a BS detecting circuit. Anyways ... thanks for all the info and explanations. I just installed a 9600GT so I have some tweaking to do.