You heard the beeps. Obviously that is good. What are the beeps telling us?
First, your motherboard is running. Why the beeps? Because switches 5 and 6 on SW1 are both off, the motherboard's Power On Self Test (POST) believes that a monochrome video card is attached, and tries to initialise the card. Because the POST can't find a monochrome video card, it beeps the speaker (1 long, 2 short).
Second, the power supply is outputting at least two things: 1. +5 volts; and 2. POWER GOOD signal.
Now, you reassemble your computer device by device. Test the computer after you add each device. At some point, the computer will stop working, and then you will know that the last device added is the cause of your computer's failure.
The first device to add should be your video card. Before you do that, you will need to restore the settings of switch 5 and 6 on SW1 according to the type of video card you have.
||: Monochrome card (MDA)
||: CGA card
||: EGA card or VGA card
So set those switches, plug in your video card, attach your monitor to the video card, and see if you get something displayed on the monitor when you turn on the computer.
If you have a 5150 computer, note that you won't see a memory count (like the 5160 displays). Instead, expect to see a flashing underline cursor for the first minute.
After about a minute, expect to see/hear the A: drive being accessed.
If you didn't see a display AND you didn't see/hear the floppy drive being accessed (after about a minute), it is highly likely that your video card is the faulty device, either overloading the power supply, or faulty in some other way.
If you didn't see a display but you did see/hear the floppy drive being accessed (after about a minute), consider the following:
* The monitor may be the wrong type for the video card.
* You may have a faulty monitor.
* The brightness control on the monitor may be turned down too low.