Dell T3500 with E139765 on motherboard. LED on motherboard is yellow & system will not boot up.

https://www.dell.com/support/article/ca/en/cadhs1/sln288786/precision-t3500-t5500-t7500-workstations-diagnostic-lights-and-beep-codes?lang=en

The lights alone don't tell enough to tell you how to fix it ACPI S3
Suspend to RAM Windows Standby State.
Does it boot if you use a recovery disk or an emergency boot DVD or USB stick?
Detach all the hard drives and peripherals, pull out all the memory except one, Try again. What is the result?
Try it with a different memory module alone, Repeat.
See if you can isolate a bad memory module
Or it could be a bad motherboard. Shut down and unplug, Inspect the capacitors on the board. are any of them swollen, split or leaking?

https://www.dell.com/community/Desktops-General-Read-Only/Precision-T3500-error-3-4-loud-fan/td-p/4593093

https://www.dell.com/community/Precision-Fixed-Workstations/T5500-diagnostic-lights-3-amp-4/td-p/6066338

Yes, you'll get that error message if SATA Operation (SATA Mode) is set incorrectly in BIOS setup.
And make sure that motherboard battery is good too.

An amber light means your computer isn't reading the hard drive or CD right, Take it to a professional to get this corrected

Blinking Amber - System fault error condition including Power Supply (only +5VSB working), V reg (Voltage Regulator) failure, missing or bad CPU etc.1 and 3 LED"s indicatesMemory configuration error.
Just to make sure thatnothing else is causing the problem, remove any PCI cards like modem, videocard, sound card, etc... Remove the memory modules and disconnect cables toCD/DVD drives. Look at the USB ports to see if any are damaged.

Dell Bluford e139765 motherboard:
Chipset: Intel 845GL with ICH4 southbridge Socket: 478 CPU Support: s478 Intel Celeron and Intel P4 400/533 FSB (BIOS rev A04 or newer required for latest models) RAM Support: 2x DDR PC2100 128MB-512MB (non-ECC) Sound Card: Analog Devices ADI 198x Integrated Audio Form factor: Non-ATX LAN: Broadcom BCM4401 10/100 USB: 4

That is a DELL board, their website should have a manual for it.

Look at the board really close you'll see it at the bottom right corner, SPKR, RSW, PSW, and so on, try one at a time, until you get it

Could be a couple of things.

Disconnect the C drive and see if the computer will stay turned on. If it does (you'll get an operating system not found error), then reconnect the c drive and see if you can get into the BIOS. If not, you'll need to replace the hard drive.

Could also be a faulty power supply. As soon as it tries to boot off the hard drive, it puts too much strain on the PS and causes a reboot.

Finally, if neither of those fix the issue, then the problem is motherboard and at that point it is more cost effective to replace the computer unless you can find a cheap, used motherboard. Good luck!

go to below link.....refer the diagram

http://support.dell.com/support/edocs/systems/dim2350/techov.htm#1101565

some dells have a weird port for the front panel from there case, you motherbard might be one of these.