295GTX ocp/ovp needed

[Dualist]

Got a two card 295GTX ref that needs either the ovp or the ocp doing.
Everytime I hit 1.4v core or above it black screens as soon as I run a bench. Found no end of info on the single card but not the two card version.
It has a VT1165MF controller if thats any help.

[Dualist]

Pics...

Master...



Slave...



Data sheet...
http://www.4shared.com/document/ZYOO...REGULATOR.html

[ARandomOWL]

Have you checked KPC? Mod should be similar to other cards with Volterra chip. If I have time to read through the datasheet I will give you a hand.

[Dualist]

I've search all through Tins threads and can't find anything, Sham did mention the 'sense' connectors but not what I do with them.
So will see if Tin comes back and confuses the hell out of me
Thanks mate.

[ARandomOWL]

For future reference: http://kingpincooling.com/forum/show...&postcount=166

[Dualist]

For future reference: http://kingpincooling.com/forum/show...&postcount=166

Yeah, thing is he shows the same card twice, the volterra's are rotated on the other card so don't totally trust him.

[ARandomOWL]

Trace the resistor back to the IC and find the same resistor on the other card. Chances are they use the same layout anyway.

[Dualist]

Yeah if you spin my pics it's 180 out so all good.

Anyhoo, I prodded about with my dmm and found that GND, Vnom- and Sense- are linked to the top of that resistor, I did worry as they are the other side of the IC not close to that resistor at all.
And the bottom of the resistor is connected to R_SEL4.
According to the data sheet Imax setting programmed by R_SEL4(A).



But don't know what vr to put on there now, did some resistance tests and got this lot...
@ 2000k I got... 311
@ 200k I got... 48.8
@ 20k I got... 7.43

Any ideas.? Told you I was n00b.

[ARandomOWL]

You need to refer to Table 1A/1B too. I don't have any experience with these chips so I'm not going to try and fudge some advice

[Dualist]

No problem mate, atleast you're honest

Have done a little more reading as I found a mod section that didn't come up on google...
http://www.ocxtreme.org/forumenus/showthread.php?t=4394

Turns out Kingpin and Sham didn't do the ocp, they replaced some chokes according to Andre.

But I can't do that, so as the Volterra is the same on the 285 I'm gonna attach the same 100k vr to that resistor and see if I can get a reading of 15k with them in parallel and go from there. Shouldn't be to bad as I'm getting 7.43k (?) to start with.
http://www.xtremesystems.org/forums/...PU-and-OCP-mod

Here goes nothing

[ARandomOWL]

No problem mate, atleast you're honest

Have done a little more reading as I found a mod section that didn't come up on google...
http://www.ocxtreme.org/forumenus/showthread.php?t=4394

Turns out Kingpin and Sham didn't do the ocp, they replaced some chokes according to Andre.

But I can't do that, so as the Volterra is the same on the 285 I'm gonna attach the same 100k vr to that resistor and see if I can get a reading of 15k with them in parallel and go from there. Shouldn't be to bad as I'm getting 7.43k (?) to start with.
http://www.xtremesystems.org/forums/...PU-and-OCP-mod

Here goes nothing

When connecting two resistors in parallel, the net resistance is always smaller than the smallest resistor. ie. 100k and 7.43k in parallel: net resistance is less than 7.43k (actual value given by this equation).

Another thing you have to remember is, when you're measuring resistances in-circuit, semiconductor devices and capacitors can interfere with the reading (your voltmeter produces a voltage across it's terminals in order to measure resistance). A reliable way to find the value of a resistor in-circuit is to read it's value code. Unfortunately, tiny SMD resistors aren't always labelled.