Soyo k7v dragon plus motherboard continuous
At the age of *********** board, I would recommend physically looking at the board, in particular, the large upright capacitors. If the tops are bulging, or have anything leaking out of them, send the board to a recycler, and look for an exact replacement on the used market, or replace with new. I just bought the same board you have today for $25, with AMD 1800 CPU.
At 10 years of age, the battery is probably past due for replacement
too. It is a standard CR2032 3Volt battery. If you replace it quickly, you may not loose your BIOS settings.
If you have a volt meter, you can check your power supply voltages. Again, your manual will show what voltages to expect at each power connector pin. A range of +/- .05V is generally allowable on all sources.
Also try unplugging all boards and powering it up. The beep should change to a sequence of 2-1-3-1 beeps, indicating that it's not able to see the video card. If you still only get a repeated long beep, It's possible that the CPU itself may have died. These are also available very cheap at this point. The fact that you are getting a cycling beep indicates to me that the CPU is OK though.
I looked up beep patterns and did not find anything for one long repeating beep for the Phoenix BIOS on your board. There is no mention of them in the Soyo manual either.
Last resort is resetting your BIOS settings to "First Birthday", and try again. This will require you to re-set any manual settings you had set previously (probably 10 years ago). This is done by moving the jumper located between the green LED, and the battery, to the two pins nearest the LED, for a second, and then back to the position nearest the battery.