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Image Quality - Low Pass Filter Mod GTX 260 - Need Help

post #1 of 13
Thread Starter 
I'm looking for some advice. This isn't technically a volt mod, but I figured this is the most appropriate place to post this. In short, I want to improve image quality by desoldering specific capacitors to prevent low pass filtering on the video.

Here's a bit more detail, I read recently about mods on old graphics cards to bypass low pass filtering performed on the analogue outputs. This low pass filtering was designed to reduce RFI, but a side effect was that it degraded image quality. I have some CRTs still in use that require analogue video, and an old GTX 260 lying around that I don't mind sacrificing.

These old mods are documented here:
http://www.anandtech.com/show/869/5
http://web.tiscalinet.it/creeping_death/guide/aamodifica.htm#pixelview2mx
http://www.anandtech.com/show/934/6

Can anyone help me adapt these mods to the GTX 260? I assume that they still apply.

I've attached some photos of my PCB. The video outputs on this graphics cards from top to bottom are HDTV out, and 2x DVI-I. I believe what they call HDTV out is component video output over a mini-din connector, a breakout cable is supplied with the card.

Please click on the images below to get the full resolution versions.
IPsKzlTm.jpg
laVkGwim.jpg
S1hKgJzm.jpg
Edited by innocenceisdeath - 4/2/14 at 3:01pm
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post #2 of 13

it doesnt appear that this model GPU has any LPF on the DVI outputs.. only a set of protection diodes..

 

*fyi - your links arent working

post #3 of 13
Thread Starter 
Thanks for the input. I've updated the image links. How can you tell that there is no LPF?
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post #4 of 13

there are no capacitors located near the DVI connections.. as your web links indicated there would need to be for such filtering to be in place..

post #5 of 13
Thread Starter 
Oh? I thought that the following components near the DVI ports might be capacitors. I've highlighted them below. Excuse me if I'm wrong, I'm new to SMD electronics.

eln6y4ym.jpg VXyjVLvm.jpg

The ones on the back of the PCB look promising, as they are in sets of three, which is appropriate for RGB.
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post #6 of 13
Thread Starter 
If you look at this image instead, of a different GTX 260, you will see that more components are marked.

http://www.syndrome-oc.net/img/articles/msigtx260lightning/full-size-back.jpg

Some of the components that I have highlighted are indeed capacitors.
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post #7 of 13
Thread Starter 
So, I believe what we have here is the following layout:

Diode -> Resistor -> Capacitor -> Inductor -> Capacitor

These components are highlighted in the image below with the following colour scheme:
Green = Diode
Red = Resistor
Pink = Capacitor
Blue = Inductor
yQ3gqnim.png

This corresponds to Anandtech's report on the Geforce Ti 200, in which a set capacitors is replaced with a set of resistors.
http://www.anandtech.com/show/869/5
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post #8 of 13
Need to do some continuity probing and mapping. Those might be transistors.

If you have inductors involved with the capacitors, it not just a LPF, but a resonant circuit, which would act more like a band pass filter.
    
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post #9 of 13
Quote:
Originally Posted by PizzaMan View Post

Need to do some continuity probing and mapping. Those might be transistors.

If you have inductors involved with the capacitors, it not just a LPF, but a resonant circuit, which would act more like a band pass filter.

 

damn good eyes, couldnt even make them out from the pic! :glasses

post #10 of 13
Thread Starter 
Quote:
Originally Posted by PizzaMan View Post

Need to do some continuity probing and mapping. Those might be transistors.

If you have inductors involved with the capacitors, it not just a LPF, but a resonant circuit, which would act more like a band pass filter.
Thanks for the advice smile.gif I will do some continuity testing.

What do you think may be transistors? What I suggested were diodes? If you look at the PCB on the SyndromeOC image (the middle DVI connection), you will see them marked as D523, D524 and D525 http://www.syndrome-oc.net/img/articles/msigtx260lightning/full-size-back.jpg
Don't labels on the PCB marked with a D usually indicate diodes? http://www.electronicrepairguide.com/images/surface%20mount%20resistors.jpg

That is a very good point about how it is creating a resonant circuit. Wikipedia indicates that RLC circuits can still be used to implement low-pass filters, and a low-pass filter makes more sense in this context than a band-pass. https://en.wikipedia.org/wiki/RLC_circuit#Filters
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