Mod's for the steady handed.

[Joe]

These are those mods that make most people cringe or think "Man you need help"

We all seen them around, and I thought they deserved their own forum!

enjoy!

[GigaFrog]

You mean this is where we post our mods?

OK, I soldered ceramic capacitors in the back of the CPU socket. When I measured the Vcore with a 400MHz oscilloscope, it was so noisy that I decided to add high frequency capacitors. They are chip surface mount (size 0603) that fit in between Vcc and Vss pins. I alternated with a 100pF, a 10nF, a 100pF, ... a total of about 50 capacitors soldered in between the FCPGA470 socket pins. I got the pinout from the CPU datasheet.

Just these ceramic caps allowed me to increase the CPU freq from 1035MHz to 1050MHz. The reduction of noise decreased the stress on the processor (by reducing overshoots).
Still, the 400MHz scope was abble to trigger between 1.95V and 2.23V, on a Vcore set at 2.05V. Unfortunately, I didn't write down the trigger levels before adding the caps, but it was probably uggly.

Considering overshoots, they were pretty high too at the leads of the electrolytic caps, so I added a 100pF and a 10nF ceramic cap between the leads of each electrolytics. Because the ceramics can handle 50V, they will absorb high freq overshoots before they even reach the electrolytics and damage them (they are rated at 6.3V). One of the first reason of failure of a motherboard is the death of electrolytic caps (they go short when they die, resulting in heavy damage to the Vcore regulation circuitry).

My Vcore is still fluctuating by 0.11V between iddle and load, and my next mod is to dynamically switch the VID pins to stabilize the Vcore. I am almost done with the circuitry that will do that, will post results.

I made all these mods at work, under binocular, with a fine tip temperature regulated soldering station. Not the kind of stuff to attempt with a 50W standard soldering iron.

[Butcher]

Yes I've seen electrolytics go bad (luckily not on a mobo).
3 in total, first went brown and made the goop on a nearby LM317 boil from heat.
Second exploded and showered me with innards, major chunk hit the floor and burnt a hole in the carpet (flew right over my shoulder).
Third caught fire and burned for about 3 seconds with a yellow/white flame. Left massive scortch marks on the board.

Luckily in all three cases the surrounding circuitry was fine.the exploding cap actually fixed the short by blowing the leads apart

[Brad]

hehe at school once we put 300v through a 6.3v cap. It literally exploded. We had it in a cardboard box, that ended up being covered by the electrolyte. It was really quite fun

[Butcher]

Hah school is great, my teacher shocked himself on a 5000V EHT supply, luckily they're internally current limited to almost nothing or we'd have been scraping him off the wall :P

[[dannzig]]

I would probably start laughing like hell if I was in the same room

[Lonely Raven]

Giga, I'm lookin to do some really close up, surface mount,
mods and I'm lookin for a good soldering iron and a REALLY good
set of Binocs or better yet, a magnifacation lamp. I've not liked
the magnification lamps I've seen so far, they were only 4X and
of rather average glass. And my soldering iron is a Weller, but
it's more of a high level hobbest then a pro grade surface mount
iron. Right now I think my iron is a WCC-100. Or is it a CWW-100.

Anywho, I'm going to be doing voltage mods on a bunch of
video cards, and a few system boards, and I've been doing
blue LED mods on Nokia phones and even though I have really
really good eyesite, my work is functional, but sloppy (IMHO).
So any suggestions, web pages to check out and such for good
gear would be greatly apprecaited.

[GigaFrog]

Hi Lonely Ravel,

I use a Weller WES50 at work, plus a Metcal soldering station. The Weller does as well as the Metcal for what I use it for, for a fraction of the price (the Metcal is ~$1K).
What you need is a good binocular microscope, like the CO-SZ-600 from Scienscope.
Stereo Zoom
They call their stuff a stereo zoom.
Wesco and Bausch&Lomb are other manufacturers.
These units are pricey (~400-500 US$) but you won't regret your investment.

Soldering Tools
Metcal Retailer
Weller Retailer

Invest in a stereo zoom, and in good fine solder tips, rather than in an expensive soldering station.
Also, to desolder properly, you need a second soldering iron, so that you can desolder each side of the component at the same time.

This may be a very usefull tool:
Dual iron station

Don't forget to ventilate your work bench, solder fumes contain nasty stuff.

So you are in the "moding" biz? I am thinking about it too.