GIGABYTE Radeon HD 7870 Windforce3 Voltage Mod?

[Bobnova]

For soldering on the resistor you're going to want an iron with a fine tip. It doesn't need to be needle sharp, but small enough to just touch that one solder point. There's a sneaky method though. It looks like that resistor is connected to the top (in the pic) end of the capacitor below it. Resistors are black, capacitors are tan/orangish. You can solder on the end of the capacitor, much easier than on the resistor.
Put some leaded solder on the solderpoint and tin the wire before you try to solder the wire to it, that will make things much easier for you.
For wire, the wires in 80 pin PATA cables are perfect.

For a vcore read point, use the positive leg of one of the filter capacitors in the power section (the points near the green sticker on the photo of the rear of the card). The side with the colored block on it (on the cap) is -, the other is +, solder the read point to the + side.

 

[N0ble]

Would soldering to the point highlighted in Red work?

Looks like it comes from R681?

 

[Bobnova]

It does come from the proper resistor, but from the wrong end. It might actually work as a core voltage read point.

For the mod points you're pretty much stuck with the bottom (in the pic) end of the resistor or the of the capacitor that it connects to. Or the pin on the voltage controller chip itself, which I do not recommend. It's a major pain.

 

[N0ble]

Think i may go with the cap then, it looks a little easier.

Then once i have a secure solder i will coat it in epoxy resin so its not moving anywhere

Im right in thinking that if i want to test if its a good voltage point that i can simply set my multimeter to 20 DCV and tap my multimeter on that point with + and - to the ground point on the card and i should get a voltage reading.

It will not short out or anything?

 

[Bobnova]

That's what I do. I use a Molex (HDD power) plug for the ground, easier than trying to hold both multimeter wires.
You won't short anything out testing voltage as long as you only touch one (1) thing at a time with the probe. If the probe touches two neighboring components it can short them to each other and POW!

So be careful when probing, but have at it


(Please note: there are rare situations where the above is not true. High voltage is one of them, very sensitive high resistance circuits is another. You don't find either one on a GPU though)

 

[N0ble]

Yep seems to be a working sense point. Reading the same voltage as afterburner.

So, in that case should i be able to wire that up to the voltage sense header on my board?
I will say that the sense header is black where as the voltage mod header is red.

Do you think there is any risk of a short if i do that?

 

[Bobnova]

I have no idea how the sense headers are labeled, but if it's a sense header it's essentially the same as a multimeter. No issues, this is what it is built to do.

 

[N0ble]

Which side of the caps should i take my voltage from for VRAM?

Left or right hand side?
Or does it not matter?

 

[Bobnova]

Which ever side is not connected to ground. One side will have 50-80 ohms to ground, the other will have zero (or something close to zero). The side with 50-80 ohms is the side to solder your sense wire to.

 

[N0ble]

Cool. I shall try that tomorrow.
Going to go round a few local electronic stores tomorrow to see if I can find 50ohm trim pots

 

[TsunamiJuan]

people have local electronics stores that actually carry stuff????

 

[N0ble]

Just for a quick update before bed. Measured the vDDR from one of those caps.
It was 140ohms before power up and 1.53v under load.

Well that's my two sense points sorted. Just need to get the soldered and test to the MB sense headers on hotwire.

 

[N0ble]

people have local electronics stores that actually carry stuff????

Haha probably not, I will find out tomorrow. Failing that I will just have to take the dive and wait two week for them to cone from Hong Kong.

 

[Bobnova]

You can do something creative like a 100ohm trimpot wired in parallel with a 100ohm resistor if they have those but not 50s. That'll give you a 50 ohm starting point that heads down to 0ohms.

 

[N0ble]

Found a supplyer in UK for 50r Trimpot, im going to order these.

http://www.rapidonline.com/Electronic-Components/50r-3296y-10-3-8-Cermet-Trimmer-Pot-68-0409


I know i need 50K for memory vmod but not sure which one to buy, as from the other site he uses a 104 50K ohm, but Rapid electronics do not have the 104.

Can you take a quick look on the site and advise me of what would be suitable for the memory trimpot?

Would this be suitable or does it not have the right wattage?
http://www.rapidonline.com/Electronic-Components/50k-3306p-6mm-Cermet-Trimmer-Pot-67-0616

 

[N0ble]

I have placed an order for these, so i hope they are right

50r 3296y 10% 3/8 Cermet Trimmer Pot
http://www.rapidonline.com/Electronic-Components/50r-3296y-10-3-8-Cermet-Trimmer-Pot-68-0409

50k 3306p 6mm Cermet Trimmer Pot
http://www.rapidonline.com/Electronic-Components/50k-3306p-6mm-Cermet-Trimmer-Pot-67-0616

 

[Bobnova]

The 50k is only a single turn, it'll be really touchy for voltage.
Essentially that one turn will take the voltage from +0.05v to +12v, why it has the trimmer label on it I have no idea.
The 50ohm pot should be perfect.

 

[N0ble]

The 50k is only a single turn, it'll be really touchy for voltage.
Essentially that one turn will take the voltage from +0.05v to +12v, why it has the trimmer label on it I have no idea.
The 50ohm pot should be perfect.

Oh... yeh that sounds a little dangerous....

http://www.rapidonline.com/Electronic-Components/50k-3296y-10-3-8-Cermet-Trimmer-Pot-68-0426

I have found this, but the problem with this is that its 0.5w and not 0.2w, does this matter?

 

[Bobnova]

Nope, that's fine. You could use a 50kOhm 50w trimmer if you could find one and wanted to

 

[N0ble]

lol ok, i will get those ones then

i have some 0.2 wire, will this be sufficient?