MP 1,1-5,1 mac pro 2,1 (originally 1,1) 2006 failure

[jakesh]

Hello,
a little history: In February 2019 I managed to upgrade old mac pro 1,1. I cleaned all dust away, got new CPUs, RAM, GFX card. My mac pro configuration is as follows:

• Mac Pro 2,1 (after firmware update) running el Capitan
• 2x Intel Xeon X5365 SLAED
• Radeon HD5770 1GB DDR5
• 4x FB-DIMM DDR2 4GB PC2-5300F 667MHz
• SSD

the case: There was no symptoms - when I came back to work I was unable to start the mac. Nothing happens after the Power Button is pressed: Power-on LED does not illuminate when power button is pressed, fans do not spin, and there is no boot tone or video.

Diagnostic LEDs 4 & 5 are flashing: (LED 4 CPU B (Lower Processor) Overtemp; LED CPU A (Upper Processor) Overtemp). When Power Button is being pressed these LEDs stay on red.
When DIAG_LED button is being pressed:

• the LED 1 Trickle Power slowly flashes with yellow.
• LEDs 4&5 keep flashing
• LED 6 - GPU Present OFF
• LED 7 - Power On OFF
• LED 8 - EFI Done OFF

When resetting the power supply by unplugging the AC cord for 10 seconds or even more I put the cord back the fun part starts: you can hear silent clicks. When a click occurs gfx card LED goes on, gfx fan tries to spin, other fans try to spin. Its like you try to start a car with empty battery. After 3 such clicks with less & fans it stops.
I replaced power supply unit with the same from other mac pro - no effect. I checked the PSU by installing it in that other mac pro and it works.
I removed and then replaced the CR232 Battery - no effect
I removed RAM, GFX card - still no effect
I removed all drives - no effect
I removed heatsinks and disconnected them form the logic board - Diagnostic LEDs 4 & 5 stopped flashing but mac won’t start
I removed CPUs - no effect
I placed old original Xeons back - no effect

If anyone has an idea how to revive this machine I would be very grateful.