Fixed voltage, TL494 PWM controlled regulator circuit .... I voltage only

This thread seems to have the same motherboard: Help identifying P54TA Socket 7 motherboard
I can make out from the pic F10P040 for the big schottky barrier diode, but can't make out the text from the smaller 3 legged chip.

Easiest way would be to ask user SVD then 😉

giantclam wrote on 2023-10-10, 11:34:

Fixed voltage, TL494 PWM controlled regulator circuit .... I voltage only

Correct, there is also a TL431 vref on the board, i have looked online for socket 7 boards with similiar topology with no luck

zyga64 wrote on 2023-10-10, 16:37:

Easiest way would be to ask user SVD then 😉

Thankyou

It might be best to purchase a MMX processor and go for a Necroware VRM module. And do away with the single 3.3v switching regulator on the motherboard.

Frank Grudge wrote on 2023-10-13, 06:45:

It might be best to purchase a MMX processor and go for a Necroware VRM module. And do away with the single 3.3v switching regulator on the motherboard.

Are you sure the Necroware VRM will provide the 3.3V I/O voltage? I don´t think so:
https://github.com/necroware/s7-vrm

The onboard regulator of the mainboard is still necessary for dual voltage operation. It provides 3.3V I/O while the VRM module proviodes the core voltage.

Necroware VRM can provide 3.2 which should be sufficient (for single voltage CPU).

Single voltage MMX?

You are right. I didn't read previous reply carefully 🤦

majestyk wrote on 2023-10-13, 08:02:

Are you sure the Necroware VRM will provide the 3.3V I/O voltage? I don´t think so: https://github.com/necroware/s7-vrm […]
Show full quote

Frank Grudge wrote on 2023-10-13, 06:45:

It might be best to purchase a MMX processor and go for a Necroware VRM module. And do away with the single 3.3v switching regulator on the motherboard.

Are you sure the Necroware VRM will provide the 3.3V I/O voltage? I don´t think so:
https://github.com/necroware/s7-vrm

The onboard regulator of the mainboard is still necessary for dual voltage operation. It provides 3.3V I/O while the VRM module proviodes the core voltage.

I see your point i havnt looked at the pinout for the VRM module thanks.

Frank Grudge wrote on 2023-10-15, 02:36:

majestyk wrote on 2023-10-13, 08:02:

Are you sure the Necroware VRM will provide the 3.3V I/O voltage? I don´t think so: https://github.com/necroware/s7-vrm […]
Show full quote

Frank Grudge wrote on 2023-10-13, 06:45:

It might be best to purchase a MMX processor and go for a Necroware VRM module. And do away with the single 3.3v switching regulator on the motherboard.

Are you sure the Necroware VRM will provide the 3.3V I/O voltage? I don´t think so:
https://github.com/necroware/s7-vrm

The onboard regulator of the mainboard is still necessary for dual voltage operation. It provides 3.3V I/O while the VRM module proviodes the core voltage.

I see your point i havnt looked at the pinout for the VRM module thanks.

You can try to use single voltage CPUs on your motherboard with Necroware VRM (with broken onboard regulator) - if there aren't more broken elements.
I can confirm that on Shuttle HOT-541 with onboard regulator disabled, Pentium-S 120 works just fine on 3.2V setting.

However, you can try to repair it -inductor can be self made - we can see from photo in the other thread, that original one has 21 loops, and diameters of the ferrite cores are standardized - you can measure ring on motherboard and choose the "slightly smaller one" 😀 There is also thing called permeability (μ'), but usually same color of ferrite toroid with the same diameter means same permeability (but not always). https://coil32.net/online-calculators/ferrite … calculator.html
Double Shottky diode can be borrowed from old ATX PSU. And third element (probably mosfet) can be guessed if you try to draw part of schematics containing TL494, Shottky, mosfet and inductor (and small elements close to them)... Especially the way how those three are connected to TL494.

Maybe I'm too optimistic, but why not to try 😀

zyga64 wrote on 2023-10-16, 08:14:

You can try to use single voltage CPUs on your motherboard with Necroware VRM (with broken onboard regulator) - if there aren't […]
Show full quote

Frank Grudge wrote on 2023-10-15, 02:36:

majestyk wrote on 2023-10-13, 08:02:

Are you sure the Necroware VRM will provide the 3.3V I/O voltage? I don´t think so:
https://github.com/necroware/s7-vrm

The onboard regulator of the mainboard is still necessary for dual voltage operation. It provides 3.3V I/O while the VRM module proviodes the core voltage.

I see your point i havnt looked at the pinout for the VRM module thanks.

You can try to use single voltage CPUs on your motherboard with Necroware VRM (with broken onboard regulator) - if there aren't more broken elements.
I can confirm that on Shuttle HOT-541 with onboard regulator disabled, Pentium-S 120 works just fine on 3.2V setting.

However, you can try to repair it -inductor can be self made - we can see from photo in the other thread, that original one has 21 loops, and diameters of the ferrite cores are standardized - you can measure ring on motherboard and choose the "slightly smaller one" 😀 There is also thing called permeability (μ'), but usually same color of ferrite toroid with the same diameter means same permeability (but not always). https://coil32.net/online-calculators/ferrite … calculator.html
Double Shottky diode can be borrowed from old ATX PSU. And third element (probably mosfet) can be guessed if you try to draw part of schematics containing TL494, Shottky, mosfet and inductor (and small elements close to them)... Especially the way how those three are connected to TL494.

Maybe I'm too optimistic, but why not to try 😀

Many thanks for your response this gives me some direction i will try substitute parts and trace out the TL494 topology to find a suitable mosfet 😀 cheers

And don't forget to replenish the missing RTC chip (Dallas DS12887) or a modern replacement such as https://github.com/necroware/nwX287

majestyk wrote on 2023-10-13, 09:41:

Single voltage MMX?

Use 2x necroware VRMs
Merry Christmas