Memory not detected

[lbwlow]

Bought a Compaq Presario CQ3200 desktop from a junker (yet again ). I wanted the casing for my other project, but it come with mobo, processor and PSU that all.

The board looks to be in good shape, so i decided to test it. It won't turn on, and my PSU is making a weird clicking noise (very very inaudible), further checks found a SMD capacitor and a chip near it was burning hot. After removing the shorted SMD cap (i guess?) the nearby chip that i mention doesn't heat up no more. And now the board is able to turn on, but with/without RAM it beep 1 short, 1 long (memory error). Then i resolder another similar sized SMD cap, this time both the cap and chip doesn't heat up anymore, but still throwing me with the same beep code. I am guessing the chip could be fried.

The burning hot chip is a SC4215A. After looking the datasheet, it is a 2A regulator with adjustable output from 0.5-3.8V. Is this the chip that control power to the RAM ? I have uploaded the datasheet. I have tested voltage output on MOSFET around the RAM area, all of them are outputting the correct voltage. I test those MOSFET on their middle tab, is this the correct way to test for voltage on the MOSTFET ? Please correct me if i am wrong

In red is the location of the SMD cap and yellow is the chip:


Guys, what your opinion on this ?

[goontron]

Re: Memory not detected

Not seeing RAM in the OS or BIOS?

[lbwlow]

Re: Memory not detected

^
No POST at all

[stj]

Re: Memory not detected

so is the voltage coming out of the regulator?
maybe the bad cap killed it.

[momaka]

Re: Memory not detected

so is the voltage coming out of the regulator?
maybe the bad cap killed it.

I doubt it. If a voltage is missing, motherboard will not POST at all in most cases. The fact that the motherboard beeps means that it has at least successfully gotten all power rails ON and ready.

To lbwlow: check voltage going to the RAM. The coil and silver cap next to the RAM slots should have 1.8 Volts on it, I think. There should also be RAM Vtt somewhere - this is usually about 1/2 of RAM Vdd, or 0.9V (though it can be as high as 1V for DDR2).

Here is what I am thinking:
Are the memory modules you use to test the system a good quality brand?
Just because your memory modules work in another PC doesn't mean that they are good. I know this, because I've seen cheap Buffalo DDR memory consistently not work in Dell PCs but work fine in other motherboards that booted with the memory underclocked by default. Moreover, the Dell motherboards in your other thread here seem to be having the "Dell Turbo Fan Syndrome", which is typical when the PC has problems with detecting memory (at least for Dell).

So I suggest trying a good brand-name memory module (even if it is a measly 256 MB). Something like Samsung, Hynix, Nanya, Micron, and Kingston would be preferable. Avoid Infineon and Corsair.

Also, can you take a picture straight from top that captures the memory slots and the area around them (particularly where that hot SC4215A regulator is)?

[stj]

Re: Memory not detected

i just read the datasheet.
that cap you replaced needs to be atleast 10uf

meter the voltage across it.