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Discussion Starter · #1 ·
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
 

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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..
 

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Discussion Starter · #5 ·
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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Discussion Starter · #7 ·
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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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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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
 

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Discussion Starter · #10 ·
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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Quote:
Originally Posted by CL3P20 View Post

damn good eyes, couldnt even make them out from the pic!
nerdsmiley.png
I was viewing from my tiny 4" display on my phone
tongue.gif

Quote:
Originally Posted by innocenceisdeath View Post

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
Yes, "D" generally means diode on the PCB print. Probe the SOT23 three leg package and verify that. Should have resistance one direction and no resistance with probes switched. If you can't get one of the legs to show any resistance it might be a jfet, but likely your assumption is correct and it's a diode.

Yes, you can have both C and L components and still be low pass. Need to full map the configuration to know for show how the circuit is setup. They can be used in so many different configurations, making the wrong mod could increase the lower critical frequency and have the adverse effect of you goal. Would be nice if we could get the values of the capacitors and inductors. Will help with finding the right value resistor to replace in the mod.

All in all, I think you're on the right track. I'm curious if the completed mod will yield a visibly noticeable improvement.
 

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Discussion Starter · #12 ·
Quote:
Originally Posted by PizzaMan View Post

Would be nice if we could get the values of the capacitors and inductors. Will help with finding the right value resistor to replace in the mod.

All in all, I think you're on the right track. I'm curious if the completed mod will yield a visibly noticeable improvement.
I am working on this. To measure these SMD components though I need some micro tip probes for my multimeter, regular probes are far too large.
 

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Discussion Starter · #13 ·
Quote:
Originally Posted by PizzaMan View Post

Yes, you can have both C and L components and still be low pass. Need to full map the configuration to know for show how the circuit is setup. They can be used in so many different configurations, making the wrong mod could increase the lower critical frequency and have the adverse effect of you goal. Would be nice if we could get the values of the capacitors and inductors. Will help with finding the right value resistor to replace in the mod.
Ok. So I've measured some of the components. I haven't been able to measure the inductors, what is the best way to do this?

AA42olCm.png

I am not sure how accurate the measurement of the 0.3Ω resistors are, the measurement may be a bit fine for the multimeter used.

The yellow circles indicate test points which I believe are before the inductors, resistors and capacitors. Would soldering on new connections here bypass the filtering?
 
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