need some help locating the "sense" pin [Archive]

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m4rtin

11-07-2005, 03:33 PM

I have never done v-mod before and so I took my old ATI'is graphics card and thought, that it would be a good for practice. So I tried to locate the chip, whitch controls the current on the PCB. The GPU is ATI 3D Rage Pro Turbo (http://img438.imageshack.us/img438/2161/img16940gp.jpg). I dont know the manufacture, but it seems to me, that this card is made by ATI himself. Anyway, the card has only three chips- GPU and other two.
The card and other two chips on it:
http://img436.imageshack.us/img436/3862/img169447vk.th.jpg (http://img436.imageshack.us/my.php?image=img169447vk.jpg)
http://img436.imageshack.us/img436/1609/img16975jx.th.jpg (http://img436.imageshack.us/my.php?image=img16975jx.jpg)
Is the chip with 14 pins, the one, which controls the current, or is it the 8 pin chip?

If it is the 14 pin chip, then which pin is the "sense" ? I did some research by myself too. On that chip stays- 89AD66F LS125A. So is the name of that chip LS125A ? I googled a little bit and finally found this (http://www.alldatasheet.com/view.jsp?Searchword=LS1). However, which one is the right manual :) ?

Yeah...a lot of questions, but any help and questions are most welcome :rolleyes:

SikaRippa

11-07-2005, 11:58 PM

I have never done v-mod before and so I took my old ATI'is graphics card and thought, that it would be a good for practice. So I tried to locate the chip, whitch controls the current on the PCB. The GPU is ATI 3D Rage Pro Turbo (http://img438.imageshack.us/img438/2161/img16940gp.jpg). I dont know the manufacture, but it seems to me, that this card is made by ATI himself. Anyway, the card has only three chips- GPU and other two.
The card and other two chips on it:

If it is the 14 pin chip, then which pin is the "sense" ? I did some research by myself too. On that chip stays- 89AD66F LS125A. So is the name of that chip LS125A ? I googled a little bit and finally found this (http://www.alldatasheet.com/view.jsp?Searchword=LS1). However, which one is the right manual :) ?

Yeah...a lot of questions, but any help and questions are most welcome :rolleyes:

Hi,

LS125A should be a logic circuit, and it is not likely part of regulator. The other chip with label "431" (?) could be voltage regulator (shut type, zener). Datasheet fot that can be found here

http://www.national.com/ds.cgi/LM/LM431.pdf

Could you measure voltage of pin #1 ("1" is at the corner near "dot") for that chip ?

Modifying voltage of that is chip relative easy, take a look page 7 of that document. You should decrease value of R2 i.e. connect parallel (between pins 7&8) a variable resistor (high value first!!). I suggest to measure corresponding value in order to select Vres at correct range.

m4rtin

11-08-2005, 06:53 PM

craig588

11-08-2005, 07:00 PM

SikaRippa

11-09-2005, 03:12 AM

The lable of the other chip is

431
88N

Measuring:
http://img462.imageshack.us/img462/8468/img16975jr.th.jpg (http://img462.imageshack.us/my.php?image=img16975jr.jpg)
431
88N:
#1 = 2,47 V
#2 = 0 V
#3 = 0 V
#4 = 0 V
#5 = 3,31 V
#6 = 0 V
#7 = 0 V
#8 = 0 V

just for case I measured that LS125A chip as well:
#1 = 4,97 V
#2 = 1,5V V
#3 = 0,35 V
#4 = 0 V
#5 = 0 V
#6 = 0 V
#7 = 4,17 V
#8 = 0 V
#9 = 3,39 V
#10 = 3,69 V
#11 = 0 V
#12 = 0,02 V
#13 = 0,12 V
#14 = 0 V

So the voltage of the 431 chip at the pin #1 is 2,47 V :)

How can I measure the corresponding value ? I have two variable resistors by Bochen 3006P 502 (20 turn; 5k) at home...might they be OK?

And what do you mean by connecting high value first?

OK.. so the code is correct ! Some comments:

- The standard way to number pins is ~ '1 near the dot, then counter-clockwise). So the number you gave are a little bit confusing, please take a look that datasheet. The number I used are related those found in datasheet.
- 3.3 V is output voltage, 2.72 V is reference voltage. Adjusting 431-regu the output voltage is modified. We do not know whether this is Vmem/Vcore ! Could you chech/verify (e.g. googling info about the memory/core chips which is allowable/normal voltage of those chips)
- 100 kohm would be allways godd starting point. You could use exact values, if you know values for R1 and R2. Could you measure resistance (power off!) between pins 1-2 and 7-8 (datasheet numbers) ?

EDIT: In addtion to those resistance values, also resistance between pins 1-8 could be helpfull.

m4rtin

11-10-2005, 12:23 PM

Use something high like 100K ohms to make sure you don't burn out the card right away when you boot it up modded for the first time. Any time I design my own mod for brand new (Or just hardware no one else has bothered to mod) hardware I always start with 100K.
I bought new ones- 100K 44om (http://www.mouser.com/catalog/614/346.pdf) ;)

- The standard way to number pins is ~ '1 near the dot, then counter-clockwise). So the number you gave are a little bit confusing, please take a look that datasheet. The number I used are related those found in datasheet.
jep...sorry :) I thought that you meaned that (http://img409.imageshack.us/img409/7962/img16978tf.jpg) "dot" but ofcourse...it was the dot on the chip (http://img409.imageshack.us/img409/1217/img169772hk.jpg) :) Is the pin near the dot alwayse #1 ?

You could use exact values, if you know values for R1 and R2. Could you measure resistance (power off!) between pins 1-2 and 7-8 (datasheet numbers) ?

EDIT: In addtion to those resistance values, also resistance between pins 1-8 could be helpfull.

Resistance between pins:

1 - 2 = 510 ohm
7 - 8 = no resistance
1 - 8 = no resistance

How does these values help me?

Could you chech/verify (e.g. googling info about the memory/core chips which is allowable/normal voltage of those chips)
I found only one answer- GeForce 256 (Asus V6600 deluxe) (http://xtremesystems.org/forums/showthread.php?t=33950) :(

Could you explain me the page nr 7 in this (http://cache.national.com/ds/LM/LM431.pdf) document (or give something instructional to read) ? And has'nt this 431 chip any "sense" pin?

SikaRippa

11-10-2005, 02:02 PM

I bought new ones- 100K 44om (http://www.mouser.com/catalog/614/346.pdf) ;)

jep...sorry :) I thought that you meaned that (http://img409.imageshack.us/img409/7962/img16978tf.jpg) "dot" but ofcourse...it was the dot on the chip (http://img409.imageshack.us/img409/1217/img169772hk.jpg) :) Is the pin near the dot alwayse #1 ?

Resistance between pins:

1 - 2 = 510 ohm
7 - 8 = no resistance
1 - 8 = no resistance

How does these values help me?

I found only one answer- GeForce 256 (Asus V6600 deluxe) (http://xtremesystems.org/forums/showthread.php?t=33950) :(

Could you explain me the page nr 7 in this (http://cache.national.com/ds/LM/LM431.pdf) document (or give something instructional to read) ? And has'nt this 431 chip any "sense" pin?

Vres of 100 kohm is safe, and you can make even more safe mod if you put a fixed resistor is series at first (some kilo ohms)

--

Dot is usually at corner of the first pin (packages having pins in all four sides have more complex logic ;) )

--

Resistor values are somehow wierd, since there SHOULD be measurable resistance between all those nodes. Maybe they have used more complex circuit..

--

431 does not have a sense pin (like some regulators) it have 'Reference' input.

--

Before test any mod I suggest to find out the voltages of Vcore/Vmem. Could you measure voltage over those yellow (tantalum) capacitors, I wonder those are for Vcore/Vmem voltages. Are there any components on the bottom side of the card ?

m4rtin

11-10-2005, 06:05 PM

Vres of 100 kohm is safe, and you can make even more safe mod if you put a fixed resistor is series at first (some kilo ohms)
could you explain it a little? As I understand, then I should connect few (2 - 3) resistors, with a constant resistance (~1 ohm), with eachother and put them between the chip and the 100K ohm Vres ?

Resistor values are somehow wierd, since there SHOULD be measurable resistance between all those nodes. Maybe they have used more complex circuit..

I checked up those resistor values once more. The resistance between pin 1 and 2 had changed for some reason and was ~0,4 k ohm's and it fluctuated a little ( I measured the resistance between pin 1 and 2 about 10 times and the value changer almost every time for some reason :confused: ). However the the resistance between pin 7 - 8 and between 1 - 8 was same- nothing. It wasn't even zero. It looked like the multimeter can't show the value, thought I tried from 200 ohm to 2M ohm. And one more thing- measuring resistance between pin 7 and no matter which other pin, gave were no value. Measuring resistance between pin 8 and no matter which other pin, gave were no value :confused:

431 does not have a sense pin (like some regulators) it have 'Reference' input.
could you explain a littlebit what is the main difference between sense pin and reference input? or give some link (I googled a little but I found only quite complicated literature about "reference" input)?

Could you measure voltage over those yellow (tantalum) capacitors, I wonder those are for Vcore/Vmem voltages. Are there any components on the bottom side of the card ?
No, there are any other components on the bottom side of the card.

http://img488.imageshack.us/img488/6594/img16943ye.th.jpg (http://img488.imageshack.us/my.php?image=img16943ye.jpg)

#1 - 3,39V
#2 - 0V
#3 - 3,33V
#4 - 0V
#5 - 3,37V
#6 - 0V
#7 - 3,31V
#8 - 0V
#9 - 3,39V
#10 - 0V
#11 - 5,02 V
#12 - 0V

SikaRippa

11-11-2005, 07:14 AM

could you explain it a little? As I understand, then I should connect few (2 - 3) resistors, with a constant resistance (~1 ohm), with eachother and put them between the chip and the 100K ohm Vres ?

1 fixed resistor having value of some kilo ohms at series with Vres = guarantees you never have SHORT when adjusting

I checked up those resistor values once more. The resistance between pin 1 and 2 had changed for some reason and was ~0,4 k ohm's and it fluctuated a little ( I measured the resistance between pin 1 and 2 about 10 times and the value changer almost every time for some reason :confused: ). However the the resistance between pin 7 - 8 and between 1 - 8 was same- nothing. It wasn't even zero. It looked like the multimeter can't show the value, thought I tried from 200 ohm to 2M ohm. And one more thing- measuring resistance between pin 7 and no matter which other pin, gave were no value. Measuring resistance between pin 8 and no matter which other pin, gave were no value :confused:

OK.. there is SOME resistance between nodes. Fluctuations etc. might be caused be capacitors and/or active components connected also to those nodes.

could you explain a littlebit what is the main difference between sense pin and reference input? or give some link (I googled a little but I found only quite complicated literature about "reference" input)?

Sense-pin can be found some (switching) regulator chips, used to sense current level of output. This kind of regu have 'Reference' which controls output voltage (see page 3 of that datasheet)

No, there are any other components on the bottom side of the card.

http://img488.imageshack.us/img488/6594/img16943ye.th.jpg (http://img488.imageshack.us/my.php?image=img16943ye.jpg)

#1 - 3,39V
#2 - 0V
#3 - 3,33V
#4 - 0V
#5 - 3,37V
#6 - 0V
#7 - 3,31V
#8 - 0V
#9 - 3,39V
#10 - 0V
#11 - 5,02 V
#12 - 0V

Lets' see... There is ~ 3.3 V in all capacitors except one. Since this kind of regu cannot provide high current (enough for core/memories) without power MOSFET's/bipolar, so I think the 3.3 V is taken direct from AGP. This is purely assumption, because I cannot see/identify all components from that foto. In that case the '431' would generate only (?) a reference voltage for some circuit and not a supply voltage.

Anyway, you could test modifying output voltage carefully with Vres and measure if any of those voltages will change. After that (if succeeded) you could test OC-capability to see any difference...

m4rtin

11-17-2005, 04:39 PM

I'm sorry I could'nt answer earlier :(

1 fixed resistor having value of some kilo ohms at series with Vres = guarantees you never have SHORT when adjusting
I bought a fixed resistor having value of 2 kilo ohms. That should be fine (should the value of the resistor be a littlebit lower than the value of the output voltage?) ?

Anyway, you could test modifying output voltage carefully with Vres and measure if any of those voltages will change. After that (if succeeded) you could test OC-capability to see any difference...
ok...but how do I have to increase the output voltage? I made a little figure, but I'm afraid, that this is a total crap, because I am rather stupid in electronics :(

SikaRippa

11-19-2005, 10:09 PM

I'm sorry I could'nt answer earlier :(

I bought a fixed resistor having value of 2 kilo ohms. That should be fine (should the value of the resistor be a littlebit lower than the value of the output voltage?) ?

ok...but how do I have to increase the output voltage? I made a little figure, but I'm afraid, that this is a total crap, because I am rather stupid in electronics :(

I am little bit hurry now, short comments...

- You series connections shows OK
- To increase voltage add that 'series connection' between 'reference and anode' pins 8 & 7 (take a look that datasheet carefully to get idea)
- Adjust Vres carefully and measure all ~3.3 V nodes, after adjusting a little bit make tests with OC-ing to see difference

m4rtin

12-28-2005, 10:35 AM

I am little bit hurry now, short comments...

- You series connections shows OK
- To increase voltage add that 'series connection' between 'reference and anode' pins 8 & 7 (take a look that datasheet carefully to get idea)
- Adjust Vres carefully and measure all ~3.3 V nodes, after adjusting a little bit make tests with OC-ing to see difference

ok...so I may add that "series connection" between pins 8 & 7; 8 & 6; 8 & 2; 8 & 3 (I mean I can shoose one of those variants) ?
http://img415.imageshack.us/img415/4459/referenceanode5hi.jpg

I made a plan as well :D Is that correct ?

http://img442.imageshack.us/img442/8366/seriesconnection3cs.th.jpg (http://img442.imageshack.us/my.php?image=seriesconnection3cs.jpg)

SikaRippa

01-01-2006, 12:07 AM

ok...so I may add that "series connection" between pins 8 & 7; 8 & 6; 8 & 2; 8 & 3 (I mean I can shoose one of those variants) ?
http://img415.imageshack.us/img415/4459/referenceanode5hi.jpg

I made a plan as well :D Is that correct ?

http://img442.imageshack.us/img442/8366/seriesconnection3cs.th.jpg (http://img442.imageshack.us/my.php?image=seriesconnection3cs.jpg)

Yes, you can utilize any of those 'anode' nodes. I picked adjacent numbers just to keep it simple ;)

The schematic diagram is just fine. Start with the maximum vres value, measure voltage, adjust a little bit etc...