Searching for redemption with my LS-486e (need help with MB repair)

Discussion about old PC hardware.

Re: Searching for redemption with my LS-486e (need help with MB repair)

Postby Eleanor1967 » 2018-1-28 @ 22:29

Since neither one of those parts are expensive I just bought the transistors I posted before (I really should read what I buy, they are TIP142, not TIP127 as before. Also they are way bigger.) and a LP2951 chip. I just soldered the new transistor in and I now get the usual 4,9X volts when the board is jumpered for 5V and 4,5x volt when the board is jumpered for 3.3 and 4 which is atleast less than before.

Is this a sign that the transistor was at fault? And that if I would by a TIP127 it should work at 3.3 as it is supposed to? I compared the datasheets but I just don't know if the difference between these transistors can be blamed for the now lower wrong voltage.
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Re: Searching for redemption with my LS-486e (need help with MB repair)

Postby Eleanor1967 » 2018-2-04 @ 23:32

I finally got around to playing with the board again. Installing the TIP127 did the trick for me, I now get a nice 3,4x Volt again, 4 and 5 Volt setting work as well. I but since my guilt wasn't fully paid off after hurting the poor board so bad, I also soldered the him 3rd missing jumper, which wasn't there from the factory for the FSB selection on, which now allows selecting FSB higher than 40 up to 66. Fun times benchmarking CPUs with different clock and FSB speeds are ahead :)

Thanks for all the help, I would not have done it without it.
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Re: Searching for redemption with my LS-486e (need help with MB repair)

Postby Auzner » 2018-2-05 @ 00:22

Cool, glad it worked out. That larger mosfet had different switching (slower) and current (higher) characteristics than what the circuit was designed for. So the motherboard resistors supporting its functions were not selected for that part. Good job though on keeping at it with the soldering iron to achieve what you wanted. It's interesting that in their day, these parts were evolved up to where a system builder did not need to solder anything, but with their age it's come full circle. Back then you'd probably RMA the motherboard and they'd exchange it for shipping cost.
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