Re: SMPS problems
Sharing power when you have several supplies in parallel is tricky. A slight difference in the output voltage will cause huge variations in the output currents.
To overcome this, power sup[lies that are meant for paralleling (either for increased power or for redundant operation, which means one P/S can take ove if another fails) usually employ a forced current-sharing bus. This is just an extra wire that connects together all the supplies. The voltage on this wire is a function of the current supplied by the P/S with the highest voltage. Hoever, the other supplies in the system monitor the line and each increases its output slightly, in order to deliver more current. In the end, all power supplies share the current almost equally. For more on this, go to the TI website and look for "load sharing". Here is one chip that does this.
https://focus.ti.com/docs/prod/folders/print/uc3907.html
Also, read this document **broken link removed**
In your case, you could possibly modify the new power supply by using this chip
https://focus.ti.com/lit/ds/symlink/ucc29002.pdf, especially if your power supply has remote sensing (which I doubt). However, adding remote sensing to a power supply is easy, basically a couple of resistors added to the feedback loop.
Anyway, check the system to see exactly how the load sharing is currently implemented on the supplies that work and then post again, maybe I can suggest something.