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7800GT Volt-mod

hardnrg    -   October 10, 2006


Testing the resistance:

Now you have to confirm that the mod was successful and that turning the resistors does have an effect on the resistance of the surface-mounted resistors that you soldered to. First check the 50K solder points (i.e. across that surface-mounted resistor). The original resistance is 620 ohms. Turn the 50K resistor clockwise until the resistance starts dropping. Tune the resistance down to 600 ohms.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Then do the same for the gpu surface-mounted resistor (across the resistor at the solder point) and tune it down to 220ohms.

 

Tuning down the memory resistance.

 

Then do the same for the gpu surface-mounted resistor (across the resistor at the solder point) and tune it down to 220ohms.

 

 

Tuning down the gpu resistance.

 

If the resistance does not drop or you get values that are way off what you see here, check your solder joints and check for bridging. I had a small bridge near the memory solder point which gave me a reading of ~62ohms. Checking your resistances is vital before reinstalling the card.

Increasing the voltages:

On-the-fly voltage adjustment is both very convenient and also potentially dangerous. Reinstall the card and connect the ground probe of your digital multi-meter (DMM) to a black pin of a spare molex connector on your psu. Warning: make sure the DMM is set to read DC voltage and not resistance or current! Connect the red probe to the memory voltage reading pin on the molex that you modded onto the card. Boot up the computer (after a possible short and silent prayer) and let the computer idle at the desktop. You should get a reading around 2.15V from the preparation before. The memory only has one setting unlike the gpu so you can adjust the voltage without having to run any 3d applications or games.

 

WARNING:TURN THE RESISTORS VERY SLOWLY!!

Make sure you are adjusting the correct resistor and taking the corresponding voltage reading. Turn the resistor clockwise very slowly until you start to see the voltage increase. From that point you can then increase or decrease the voltage but I would recommend you continue to turn the resistors slowly to avoid increasing the voltage to a point where it causes damage, and likewise, to avoid decreasing the voltage to a point where the graphics card crashes when heavily overclocked.

For the gpu YOU WILL HAVE TO RUN A 3D APPLICATION TO ADJUST THE VOLTAGE otherwise you will be adding to the lower 2d voltage and when the card enters 3d mode the voltage will jump to a setting that will almost certainly damage your card.

If you are running an SLI configuration then you will have to run an application or game that uses an SLI mode in order to get the second card to use its 3d voltage.

 

I would highly recommend some form of temperature monitoring when running the card with the extra voltages. RivaTuner has temperature monitoring and logging for the gpu core. The memory is not as much as a problem, just make sure it is sufficiently heatsinked and it has a sufficient supply of fresh air and they should be fine.




  1. Guide: 7800GT Volt-mod
  2. Hardcore soldering
  3. Placing the components
  4. Preparing the resistors
  5. Soldering to the card
  6. Testing the resistance
  7. Conclusion
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