Antec TruePower 550 PSU Volt mods ? ~ PART II ~

[StinkN1]

I now have some knowledge of modding this PSU , but would like to know if anyone really "knows their math" ?? ESPECIALLY ~ Hëll ‡ Fîrë / pc ice and STEvil !!! you 3 know it all !
I have this so far right ?
3.3v = 10ohm resistor + 1k vr (or 20k VR alone)
5v = 36Ohm + 10k VR
12v = 68 Ohm + 10k VR
The BIG question I have is - If you can use a 20k trimpot alone for the 3.3v sense line , would I be able to use trimpots alone for the 12v and 5v lines safely ? 50k or 100k for 5v ?? 100 or 500k for 12v ?? Also - is using the resistor + a VR safer ? Does the resistor act as a fuse ? Also are the resistors I listed supposed to be ohm or k-ohms ? I would rather go the trim-pot by itself route as it seems like less work than grounding it out and such , but I want to do it only if it is just as safe as the resistor+VR method .Lemme know please
Thanx guys

[StinkN1]

: Update : So far from what I have been told it is somewhat of a neccessity to use resistors as using Vr trimmers alone can result in voltage fluctutations ..
The problem is where in the world do I ground three seperate rated VR resistors ? Can I run them all to the same place ? Would tapping into a ground on the psu be wise ?
I kind of though that each line had it's own ground - rated to a certain spec .. Each molex has it's own black wire(s) and the ATX connector has 7-8 black wires ; so which one would I route my ground(s) into safely without throwing everything off ?

[sjohnson]

My first thoughts:

Does the Antec TP 550 have sense lines for 5v and 12v in addition to the sense line for the 3.3v rail? Most PSU's have only the 3.3 sense line, if they have any at all.

Those PSU's where I've modded the 5v rail have required modding the PSU circuit board - not something I'd recommend to anyone without high-voltage circuit experience. A small risk but a possibly deadly one.

Another question - are you sure that the 12v and 5v rails are seperate on that Antec? Many PSU's have the 12v and 5v rails generated from the same circuits. So, modding the 5v also mods the 12v.

Some PSU's with the 3.3 sense line won't "take" without the fixed resistor. Although I have modded both an Enermax and an Enhance with just the VR, no problems with stability after almost two years.

[StinkN1]

Yes , it has sense lines for all three .. Yellow w/sense is 12v .. red w/sense is 5v and orange w/sense is 3.3v !!
I am not 100 % sure that the lines are "seperate" but they do have seperate sense lines ! So I guess they are ; yes !
What about all the lines using only a VR ?
Glad you could make it to my thread !!

[sjohnson]

Like I said, some PSU's won't work without the inline fixed resistor. Only way to know for sure is to try it.

The grounds for the three variable resistors can be shared.

Do you have a link to any 5v/12v mods for the Antec, for me to study? I'm coming up with pretty much nothing on a google.

[StinkN1]

No - no links at all .. I will take a pic of the ATX connector tomorrow if you like ? Will it help at all ? I am 99% sure it is the same as an antec TruePower 430/480 ..

[Malves]

Antec True Power models have 3 individual dedicated circuits.

[sjohnson]

No, I just wonder about the range needed for the VR's.

Use of multi-turn cermet VR's is a MUST IMO. The lowest ohm VR that is larger than the largest needed resistance is best, that way you have more fine control over the voltage, plus you adjust it slowly - that's safest for the PSU and board.

[StinkN1]

ok - now you have definately lost me sj .. "The lowest ohm VR that is larger than the largest needed resistance is best" ?? Come again please .

[StinkN1]

Also - I am going to use the last ones down on this page http://www.oselectronics.com/ose_p75.htm 15 TURN 3/4" RECTANGULAR CERMET TRIMMER
Tolerance: ± 10%
Power rating: 0.75W
Maximum voltage: 300V

[sjohnson]

OK, an explanation:

Assume you need 8.9K Ohm resistance for a zero-volt change and 8.0 K Ohm to get your 3.3v rail up to 3.6 - your targeted max.

8.9K Ohm is the highest resistance you want, so an 8.9K Ohm cermet would be ideal. 10K Ohm is available as is 20K Ohm, but you want the 10K. 10K is closer to the 8.9K you want than 20K.

Clear?

[StinkN1]

I get it now , but as I said I was going to use either resistors+VR , but wanted to use vr's alone so save trouble grounding them all .. I suppose I just am going to have to do it Malves' way .. He has a truePower ..
The only reason I really want to mod all three is I read that if you do the 3.3v alone , other lines get lots lof fluxtuations if you go over 3.4v .. I would have it at 3.45-3.50 because the new motherboard I have coming is known to drop .2v on the 3.3 when under stress ..
If I do one line - might as well do um all ey ?

[sjohnson]

u sed it

[StinkN1]

sjohnson r u trying to sike me out ..

[sjohnson]

might as well do um all ey - just agreeing with you

[StinkN1]

so are my resistor and VR calculations ok ? 1/2 watt resistors + 3/4 watt vr's will not conflict with each other ?

[sjohnson]

That's OK - the sense lines use less than 1/2 watt and mixing wattages has no affect.

[StinkN1]

Okay .. Im trying to get technical as to make sure all will go well !! You guys have been helpful !! Still waiting for hell fire to get off the squatter and come on in though !!
Thanx fellas !! Any other comments or findings please lemme know !!

[Hell-Fire]

Hello guys. ;D

I highly recommend using the Cermet vs the Trimpot. The trims are a less fine tuning vr. Go with the Multi-Turn Cermet VRs (usually 15 turn if memory serves).

You dont have to use an inline fixed resistor with the vr for all power supplies, but you do have to use it for some.

No, the fixed resistor does not act as a fuse. Basically it just gives you a starting point to go from.

Doesnt truly matter which vr you use. Whether it be 10k or 20k, as they all go from 0 resistence to the max setting.....only difference is when you get into situations where you need a high base resistence to start with...say when modding certain north bridges...but thats another story. Some people use the 1k vr's on the 3.3v rail, but you have to be very careful when adjusting those as each turn means more voltage vs per turn on the 10/20k vr's.

For the rails on my Antec TP550, I used 3 47ohm fixed, and 3 Cermet Multi-Turn 10k VRs.

I know that pc ice used a vr straight inline after making his cut on the sense lines...I cant recall what psu that he was working with at the time, but every psu I have modded (4 Antec's and 3 Enermax) have all required the use of a fixed + vr scenario.

Mixing wattages wont matter in the least.

[StinkN1]

Great ! Thanx !! I was hoping someone would say no need for resistors + the VR , but seeing as how I can ground it right into my ground wire on the PSU , it's just as easy !!
Will post back how it went .. !!
Whats a trimpot ?? These are cermets right >> ?? http://www.circuitspecialists.com/level.itml/icOid/6955
and
http://www.circuitspecialists.com/level.itml/icOid/6945
Any difference between the two ?

[Hell-Fire]

Originally posted by StinkN1
Great ! Thanx !! I was hoping someone would say no need for resistors + the VR , but seeing as how I can ground it right into my ground wire on the PSU , it's just as easy !!
Will post back how it went .. !!
Whats a trimpot ?? These are cermets right >> ?? http://www.circuitspecialists.com/level.itml/icOid/6955
and
http://www.circuitspecialists.com/level.itml/icOid/6945
Any difference between the two ?

Not really, they look exactlly alike to me...except for the size, but that could be just that the pic is distorted on the one page which makes it look smaller. Either would do. I get most of my mod stuff at Radio Shack if possible versus buying off the web. Nothing sucks more than paying more in shipping than the product is worth.

This is how you want to do it if you are using the fixed + vr:



I soldered an old molex connector from a dead psu to the ground wire of the VR and then plugged that into a live molex from the TP550. A simple way to be able to disconnect the vmod versus soldering a ground somewhere so that its a permanent thing unless you desolder it.

As far as what a "Trim Pot" is, it depends on who you ask actually. Some people call the Taper Potentiometer a trim pot, when truly the Cermets are actually Trimmers in the truest sense. To put things straight, a Cermet VR is a Trimmer (Trim Pot), and a Taper Pot is just what it says it is....but they are both VR's of course. Here is a Taper Pot, which is what I was referring to about not being as fine a tuning VR as a Cermet VR, but there are instances where using a Taper is needed. The taper also has the problem of being a much larger vr which means using them in small areas isnt possible. In that case you can use other resistors/vr's/cermets in a series.

[StinkN1]

does it make any difference at all if I put the resistor and vr closer to the atx plug or closer to the psu itself ? Also one more thing . whats the difference between metal film and carbon film 1/2 watt resistors please ?

[StinkN1]

Another idea >> http://directron.com/atxextension.html
Catch my drift ?? Nothing permanent .. It would work right fellas ?

[Hell-Fire]

I wouldnt recommend using that extender unless all your wires matched up with those wires...as in sense lines, etc. If it does then it may be a good idea to try mods on it. If it works...then simply removing it clears the mods and obviously saves your warranty.

It doesnt matter where you put the resistor/vr on the cable bundle. All my latest ones have been done inside the psu housing.

[StinkN1]

If i use the extender , I wouldnt need to use sense lines though .. Would I ?