820-2733-A only LED 1 & 2 on. Fan on. No Chime and no USB

[protocold]

Without ram, the iMac will beep. Put the known good ram in, it will turn on with only LED1&2 and Fan. No Chime. No USB.

Where should I start looking?

 

[2informaticos]

To be sure, you get steady LED500/10?

Do you get 12V_S0?

Remove the CMOS cell in the process repair.
This will force the board to turn on automatically, when power is applied.

 

[protocold]

thank you.

problem resolved, turns out wrong CPU from 2010 (i3-550) was installed on this late 2009 board (same socket but not compatible)