Help-Component Replacements

[MEB]

I am attempting to learn all I can from you guys. I currently have low electronic knowledge, but hoping that will improve. I have been fortunate to have budm get me going on the repair of a Dell 2007WFPb on an existing thread. But to give him a break, and thinking this is the correct place to post my current questions here goes.

budm has identified the components shown on the 1st photo as part of 4
buck regulator circuits which exist on my USB/DC onverter board. I have been able to find at least one shorted Mosfet J598 which I have found from the forum to be equivalent to SJ598. I can find no datasheet on the
J598 but have included one from the NEC SJ598. Both I only can find on ebay and am leary. So I am including datasheets from what I think to be similar Mosfets, but I don't know enough to make that decision. Please look at the Fairchield and Infineon Mosfet datasheets included and tell me if they are or are not suitable replacements.

Also shown on the 1st photo are S4 devices which were identified as 40V, 1A Schottky diodes. budm suggests replacing them with a 40V, 2A device. Again I have included a datasheet for an SS24 which I would like to know if that may be a suitable replacement for the S4.

If my suggestions are not going to work, I would be extremely grateful to know if anyone knows or has successfully replaced the J598 Mosfet and the
S4 diode. Thanks.

[LDSisHere]

Re: Help-Component Replacements

I think the Fairchild to be a better choice than the Infineon FET to replace the J598. The choice of the SS24 as a replacement diode should be a good.

[PeteS in CA]

Re: Help-Component Replacements

The full P/N for that MOSFET is 2SJ598, and the way Japan does its semiconductor numbering, other companies cannot make equivalents and use the same part number. I may be incorrect on this, but I think NEC ceased making power MOSFETs, so you're stuck with having to find a close equivalent. The critical parameters are the voltage and current ratings, and the R(DS ON). The gate capacitances are pretty important as well. Higher current rating is OK. Lower R(DS On) and gate capacitances are good. Infineon and Fairchild are good brands; likewise IR, Siliconix and STMicro.

[MEB]

Re: Help-Component Replacements

Thanks LDSisHere and PeteS. I will obtain replacements per your advice and report back how things went.