5V mod for QTEC 550W psu?

[Mr Dead]

My 5V is running a little low for my liking, searched the web for guide on how to volt mod the psu and only come up with this guide for the 400W qtec psu. Am I correct in asuming the layout will be the same? If so all I need to do the mod is a 220 Kohm pot and a 26 Kohm resistor?

Help me before I blow myelf up or electricute myself!!!

[RichBa5tard]

I don't think they have identical layouts. You could take the risk and fry your PSU, but you might ruin your HW too...

Are you sure it isn't the motherboard that is undervolting? My unmodded 550W Qtec PSU delivers 5.03V under load (but my 8rda+ undervolts it to 4.75v...).

[PMM]

Link us to the guide m8y as I am exploring the Qtec 550 at the
mo.... I asked Qtec for a Schematic and got a no answer
but the 3.3v is a done deal I can get that up with a Diode on
the 3.3v sense and a resistor change on the board but I am
still struggling with 5v & 12v feedbacks so a link to said article
might help me to help us all, hopefully it may help identify how
they do things even if the layout is different.

[Mr Dead]

Here you go -

http://translate.google.com/translat...UTF-8%26sa%3DN

The only prob is its an italian conversion so it dosent make a lot of sense in places!!!

[PMM]

Thanks m8y

'A picture speaks a 1000 words' that alone should over come
any language problems

Hopefully there will be good piccies within to work off at least
I can do a direct compare with my 550w currently in bits on the
floor

Fingers crossed anyway.

[PMM]

just done a simple test PSU unloaded....
12v was 12.23 test = 12.62v
5v was 5.29 test = 5.45v

The QTec PSU's have a Pulse Width Modulator IC called
TL494CN.

Pin 1 of this IC is part of a error amplifier when hooked up to
ground via a suitable resistance enables you to increase the
voltage

The gain as above was from a 100K pot set at 100Kohms to
ground and pin1 via a micrograbber.

Pin1 of the IC is next to a Capacitor coded C15 or follow the
green wire to the circuit board you'll see 2 IC's the one to the
right harder to get to is the TL494CN pin 1 is in line the the actual
C15 text.

I'll let all you modders work out how best to connect your wire but
at least it works.

[PMM]

P.s. If you slice the Orange 3.3v sense wire (The thin lighter one)
and place a diode in line then replace resistor R28 that is next to
the orange wire point on the circuit board it raises the 3.3V line
as well.

I'am using a 150 Ohm resistor to get 3.6v / 3.5v in MBM.

[Mr Dead]

Im a total newbie when it comes to volt mods like this, and to be honest they scare me!! Just done the Vcore volt mod to my kx7-333R so it now tops out at 2.0 volts. Had a bit of hassle soldering the wire to pin 7 on the chip but got there in the end.

Now im running at 2.0 Vcore my +5 rail drops down as low as 4.41 when running prime95, this is not good so im gonna have to tackle this psu mod now.

Any hints or tips before I get started.

p.s. my +12V and +3.3V are fine

[C0oL]

PMM: You were correct mate, Pictures speak a 1000 words... so, erm... for us noobs out here, could we have some of those precious piccies please?

I can solder pretty well, but pictures work better for me rather than text from a page

Regards,
Dean

[PMM]

If I had a digi cam I would, only pics are those as per thread
above.


** Warning ** **Warning** **Warning**

Messing with a PSU without knowing what your doing can
damage your health or even Kill do not attempt unless you
are aware of the possible dangers and know what your doing.
PSU contains capacitors that will still have charge and can zap you.

**End warning**

See pic below sorry its a ms pain jobbie from memory.

PS also note this raises the 12v line as well so you may end
up if you use a 100K resistor a 12v line up near 12.6+V.

Also please note the PSU is cheap and chearfull and under extreme voltage & high PSU speed it still sux and my modded
431 enermax is better and runs cooler.

I would not attempt this from a freshly pulled PSU it needs a while
for charge to displace.

Ideal is disconnect from main, pull motherboard plug & jumper the
green wire to a black resulting in turning PSU on - since its
unplugged from main some of the excess charge should disperse.

take out PSU from rig.

Under the 4 screws of the panel.
remove and disconnect fan header to remove completely.
undo the 2 screws of the psu socket
pull psu socket and board out slightly from its mounting
this will give better access to the IC needed.

see pic...

follow the green wire it sits more or less between to IC2
the one on the right is the one in question.

it has 16 pins I have numbered 3 of them in pic.

for the mod to work attach a wire to pin one and a suitable
100 Kohm res or varible resistor or to be safe say a 30+Kohm
fixed resistor and a 100Kohm varible for adjusting.

Now the other end of the resistor needs grounding to either
say the main grounding poing [A] or pin 7 mount point [B]
the pic shows both but only A or B needed not both.

[asw7576]

PMM... I hope that you are my angel. I've been trying to mod my generic 400watts PSU in the past 2 years.

Look at the pictures below:

Inside PSU with DR0183 Controller IC:






Diagram for output section:



Diagram for DR0183 controller IC and voltage comparator IC CP431: I suspect CP431 is responsible for feedback sensor



reference: I got these picture from: http://www.webx.dk/oz2cpu/radios/psu-pc400.htm

thanks man!!!

[tomati]

hi ,

here the link that i use for the 5vmod of the q-tec 550w

original version

http://www.pctuner.net/php/Articoli/Articolo.php?ID=226

for translate

http://babelfish.altavista.com/babelfish/tr


now , i'm looking for to mod the 3.3v and also to decrease the12v because with these vmod , when i'm running at 5v (on mofset) my 12v is at 13.0v (on mofset) , my 3.3 is at 3.09 (on mosfet )it's seem's separeted (when i turn the pot , no effect on the 3.3v rail) , i'm running with an a7v600 ( by asus) and i think that's the motherboard decrease my 5v rails .


kind regards , tomati

[bias_hjorth]

the 5v mod guide page is down.. Got another site?..

plz :-D

[STEvil]

http://www.xtremesystems.org/forums/...9&pagenumber=4



Got sense wires along side your supply wires?

[tomati]

may be tomorrow the link will be ok , i've tried it before to posted it and now i can't go on their site .

the french translation ( already good for the pictures)

http://membres.lycos.fr/pgeo/hfr/ModQ_Tec550w.doc

[asw7576]

PMM, tomati and PC Ice:

I plan to go ahead with the mod..... I think there are 3 ways to mod generic PSU with the diagram above:

1. Manipulate R45 ( 1% 34K ohm ) with smaller resistance
2. Manipulate R56 ( 1% 5K ohm ) with smaller resistance
3. Directly install another resistor to Pin 1 (3.3V limit check point) maybe with 10K VR. If this works on increasing the 3.3V line, I will add another VR to Pin2 (5V limit check point).

What do you think? Let me know if this operation is dangerous.

[bias_hjorth]

Originally posted by STEvil
http://www.xtremesystems.org/forums/...9&pagenumber=4



Got sense wires along side your supply wires?

there´s no sense wire for the 5/12v rail on the q-tec PSU.. only the 3.3V sense which I already did..

[tomati]

hi ,

i've made the vmod from pctuner for the q-tec 550w , now my 5v is ok , but my 12v is above 13v , is there a mod to decrease the 12v rail ? ( no sense wire on the 5v/12v , only on the 3.3v )

is there an overvolt or overheat protection on this psu?

kind regards , tomati.


edit : checked voltage

idle @2477mhz with1.84v vmod qtec 550w trimmer on mini (from pctuner)

3.3v rail = 3.09v on atx = 3.17v on mosfet

5v rail =4.78v on molex =4.73v on atx = 4.56v on mosfet

12v rail = 12.45v on molex = 12.47v on atx = 12.06v on mosfet

full load under toast @2477mhz with 1.84v (1.824v) vmod qtec 550w trimmer on maxi

3.3v rail = 3.09v on atx = 3.18v on mosfet

5v rail = 5.06v on molex =5v on atx = 4.71v on mosfet

12v rail = 13.5v on molex = 13.5v on atx = 12.5v on mosfet

no yet moded the 3.3v rail .

asus decrease the voltage (a7v600) on the motherboard , then i don't know what i can do more ?

[asw7576]

Ha... ha.... Finally, I did the mod for generic psu

Look at the picture below. Its CP431 which control 3.3V feedback lines. You put 10K VR in parallel to R56 ( blue resistor located between CP431 and black wires ). Slowly turn the VR to lower resistance, and you will see the 3.3V line goes up !!!

Here some resistor value:
4.4K ohm = 3.601V
5.1K ohm = 3.565V

If you see an IC similar to the picture below and its say "431" and it's location close to black and orange 3.3V cables, then congratulations!!! .... just connect a 10K variable resistor between Anode and Ref.







Hallelujah Part 2:

I find ways to increase 12V and 5V lines. Both lines increase together (3.3V line is separate mod). I increase resistance value on Pin 16 ( 2.48V voltage comparator). Higher resistance R48 ( from 43K to 50K ) actualy limits the voltage on Pin 16, and DR0183 IC respons by increasing the 12V and 5V together.

My generic PSU

12V............5V............3.3V
11.87.........5.06.........3.289 ( before )
12.55.........5.52.........3.653 ( after the mod )

[tomati]

just done the 3.3vmod on my q-tec 550w

r =10 ohm + vr = 1 kohm

3.3v = 3.09v (atx) before the 3.3vmod

3.3v = 3.36v ( atx ) at low vr after the 3.3vmod

[loggan26]

Oh I gotta ask this as I am still in the dark after reading sheet loads of threads.

For the 3.3v mod on the Qteq 550W I need a 1Kohm cermet Pot that I splice inline on the sense wire. Then I remove R28 resistor on the pcb and replace it with 10ohm resistor. Is that correct for the 3.3v mod????????????? If not then advice on which Pots or resistors I do need for the mod.

Next the 5v/12v mod. I need a 100Kohm cermet Pot and simply connect top leg to Pin 1 on the IC2. Can I do this by soldering it to the leg of IC2 on the underside of the PCB or do I have to solder it to the top on the actual leg. Ground 100Kohm with the middle leg to Psu ground (screw) etc..........

Advice needed please thanks......

[fr33ze]

does this mod make any difference to stability/overclockabilty of a motherboard.

i wanna try it because my 12v rail is at a lowly 11.3-11.5 and my 5v is normally in the 4.8 region.

also does this work in the same way for the 450w qtec power supply

[fr33ze]

just done the 5/12v mod on a qtec 450w, its uses exactly the same chip PMM was on about in the 550w version.

all i did was attach a 68K resistor to pin 1 of TL494CN to ground and it raised my voltages as follows

12v 11.67>>12.23
5v 5.13>>>5.37

idealy i'd like my 12v a bit higher without increasing my 5v too much but not a lot i can do about that.

pic for those who rnt sure what to do....

as PMM said pin 1 is just above where it says c15

[fr33ze]

just put a 150k resistor in parallel with the 65k one to make ~45k and this gave some better voltages...now
12v = 12.47
5v = 5.47

i don't wanna go much higher cuz i'll start to hit the 10% on the 5v rail

[EnZiMa]

i have a q-tec 500w, which modification I must make?

Thks