HP Pavillion RAM upgrade - wont turn on ! No POST!

I've been fixing computers for quite a while but this problem stumps me. HP Pavillion t430.uk with MS-6575 Ver 3.1 mobo (all standard). Only 256MB DDR333 (Hynix) in so was trying to upgrade it with a DDR400 512MB stick (Major). I've never ever had to match brands of RAM before and in past experience sticking in a DDR400 stick will step it down to DDR333 automatically (this is the most the motherboard can support anyway).
When i stick the 512MB RAM in, i press the power button, fans spin for a fraction of a second, power light comes on for a fraction of a second, then nothing.

Take the 512MB stick out, works fine. Take the 256MB stick out and put the 512MB in. Doesnt start up.



My main concern is that WITHOUT the 512MB stick in (i.e. factory standard) the power button doesnt seem to work too well. It needs to be held IN for a few seconds sometimes to stay on, otherwise the power will cut, and when holding the power button in for 10 seconds to force the power off, it will reboot unless i take my finger off at the right time!



Is my problem that I haven't matched brands and speeds of RAM or do I need to take it apart and have a look at swapping the PSU and etc?

I've made sure POST (and the internal buzzer) works by leaving both sticks of RAM out, and theres a relieving BEEP to show it works.

On the HP support forums someone said that the RAM doesnt meet JEDEC standards and I should only buy from Crucial or Kingston, but i've never had this problem before!

Any help would be much much appreciated! Let me know if anymore info is needed and I'll reply ASAP.



Thanks again,

Dan Gent

I have had problems (not with HP and not as extreme as the ones you report) with mixed brands of the same nominal spec.

If the HP support forums suggest a solution, I'd be inclined to go with that advice.

Not official support, just an official forum. A guy said to use crucial and kingston to make sure i get the right types. I'll try a few other sticks of RAM i've got lying around first, if they dont work then i'll order off one of those sites.
Thanks for the help :)

An update,
The 512MB PC3200 stick I used for the problem, I tested in two of my computers today on Memtest and Memtest+. Both reported thousands of errors. Could all this be down to this particular stick of memory being faulty? (although on these other two PCs it actually booted up)
Or is it possible the motherboard have damaged the RAM by giving it to high a voltage? Therefore meaning its not safe to try some more RAM, even if its same timings and speed from Kingston?

Thanks for the help so far.

Yeh it was faulty RAM. I bought some quality Corsair stuff just in case, put it in, worked first time, and memtest reported no faults after 6 hours.

Thanks for the help guys