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ASUS VL/I-486SV2G(X4) Upgrade - I really need help on electronic components.

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First post, by SETBLASTER

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For some years now i have an ASUS VL/I-486SV2G board and i always wanted to mod it. I was reading these tutorials from people that modded their ASUS VL/I-486SV2G boards and made it an ASUS VL/I-486SV2GX4 by installing some components on the motherboard that from factory were not included.

Depending on the motherboard revision, there are different topics from people that don´t visit the forum very often.

ASUS VL/I-486SV2G(X4) REV. 1.8 conversion and jumpers guide
Another high-end 486 back in action (ASUS GX4 conversion success! Tons of pictures)
ASUS VL/I-486SV2 to GX4 conversion + Am5x86 support on Rev 1.7

The list of components to buy for the mod are these:

1) LT1085CT or equivalent adjustable voltage regulator
2) N-channel power MOSFET , STP16NF06L
3) 2 x 10uf 16V and 2 x 1uf 16V tantalum capacitors
4) 330uf 16V electrolytic capacitor
5) 7407 hex buffer (an SMD model, not holes)

But as you might know, every part has many models when you try to buy them, and my problems are the following:

1) LT1085CT voltage regulator.
In digikey i get a lot different part numbers because each has a different voltage output. They are all LT1085CT but im not sure which is the correct one to buy to mod my motherboard the search i did is this one :
https://www.digikey.com/en/products/filter/po … GAHAVgMIJAXQF8g

2) N-channel power MOSFET , they mention STP16NF06L,
But this part in digikey is obsolete, but im not sure which one should i choose since there might be some differences with the obsolete one. the search i did in digikey is this one:
Digikey provides about 9 subtitutes: https://www.digikey.com/en/products/detail/st … ils-substitutes

3) am I forced to buy tantalum caps? or can i buy electrolitic capacitors instead of tantalum ?

4) this one is fine, those are the only things im shure what to buy actually

5) 7407 hex buffer
There are many different part numbers and i am not sure whats the correct one to buy.
when i search for 7407 on digikey i get these results: https://www.digikey.com/en/products/filter/bu … 9Nkg7bkJS6lF5AA

maybe someone at vogons can guide me on what part numbers i should buy at digikey
im kind of lost and don't want to ruin the motherboard

Reply 1 of 3, by BitWrangler

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Well, you really are lost or overthinking it, if you're not sure what voltage regulator to buy to enable using 3.3V CPUs.

Need the speed rating for the 7407, whether it needs to be an F or whether an ALS will do or what.

The MOSFET was already a substitution, look up the original part number from the second thread link.... otherwise you end up with a chain of this is similar to that and end up with trying to enter a giraffe in the Kentucky Derby because it's got four legs.

Unicorn herding operations are proceeding, but all the totes of hens teeth and barrels of rocking horse poop give them plenty of hiding spots.

Reply 2 of 3, by Horun

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And what version is your board?? And what cpu are you thinking of using ?
Datasheets are your friend when it comes to replacements.
If just wanting to mod the board for shits n grins but no plans on a cpu change then maybe you should rethink it.

Hate posting a reply and then have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. Stuff: https://archive.org/details/@horun

Reply 3 of 3, by kingcake

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1. Read the datasheet. Analog Devices has some of the best written datasheets in the biz. If there's something you need to know, it will be in there.
2. There are many part numbers because the LT1085 comes in multiple packages and temp/use grades. Do you know which package you need?
3. Older design linear regulators often require Tantalum caps for stability. They will often oscillate wildly with electrolytics. From the datasheet: "For all operating conditions, the addition of
a 150µF aluminium electrolytic or a 22µF solid tantalum
on the output will ensure stability." So they do say you can use a bog standard electrolytic but it must be much larger. Are you also going to bypass the adjustment pin? That's also addressed in the datasheet.
4. Soldering on a large multilayer board with many large power and ground planes can be challenging. Especially if SMD work is involved. It takes practice. I'm assuming if you don't know about datasheets or IC package sizes, you probably don't have much experience in this area.
5. This forum is largely a bad place to ask for component level electronics advice. a good 95% of posters here only know how to parrot back answers to noob questions. They will confidently tell you wrong information. I would go over to the eevblog forums. They have a newbie section for questions like these.

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