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[Tenacious]

It's hard for me to guess what you know or how much experience you have with this sort of work. I looked over both links, and they contain good info for a technician. Lets go over some stuff.

The ATX PS will power the A500 alone, right? When connected to both A500 and A530, the PS makes a distress noise and nothing powers on. When powering the A500 alone with the A530 attached to the computer but not powered, a jumper will supply 12v DC from the Amiga to the A530's fan.

If these things are true, then I beleive your A530 power connector is probably wired backward and shorting +5v to ground through the side bus. Hopefully, the crowbar protection in the PS has prevented damage to the A530. This is an easy mistake to make when looking at a connector. Does the 2nd web page show the front or the back of the power connector in the diagram? Grin.

Anyway, don't take anything else for granted. There is a logical way to check and, if needed, correct the A530's power cable connector. 1. Mate the A530 (with cover removed and the jumper installed that makes the fan run) onto the side of the A500. 2. Plug-in and power the A500 ONLY. 3. Set your voltmeter to a DC voltage range that will show both 5 and 12 volts (Not Ohms, Milli-amps, or AC-volts). The next steps are tricky, use caution and a very steady hand. Be carefull to never let a test probe touch 2 pins at once. You can use the meter to bridge between the A530's power socket and the disconnected power plug, one pin at a time. 4. Connect one meter lead to the A530's socket, pick any pin. 5. Connect the other lead to the exact mating pin on the power cable plug. Do this for each mating pair in turn. If you ever see the meter move, the signals on that pair is mismatched and causing problems. If one pair is mismatched, another pair must also be. If the meter "pegs" in the wrong direction (negative values), reverse the leads.

You can cross-check like this. Connect the black (negative) lead to the ground plane on the A530 circuit board. The ground plane is usually the large metal areas that have mounting screws going through them. Probe the socket with the red lead and record the values on a hand-drawn sketch. Do the same on the cable side and compare for like signals. Naturally, the pins that carry ground and shield will show no voltage (Gnd and Shield are connected together in the power supply). When everything matches in the power plug and socket, it should be safe to reconnect.

This is obvious, but, anytime the PS makes a distessfull sound, power off immediately. It's hard to put the smoke back into a computer once you've let it out. Grin.

[Tyball]

Thank you for writing such an elaborate explanation! As my schooldays are long gone, the little I learned about electricity has eroded somewhat. Blush.

I followed your careful method of elimination and I could only conclude that your remark about the power connector should be taken to heart. It is indeed in reverse. It says "Looking at the back of the unit" and I naturally thought the back of the A530-unit. As English is not my native tongue, I didn't think for a minute that a power connector could also be thought of as a unit.

Therefore, after switching the wires, it suddenly worked! I couldn't be more happy and then to think that I was about to give up. I love you to dead right now and I don't care what you think!

My 500 is on FIRE! (luckily without the smoke...)

[Tenacious]

Ah shucks! Now I'm red faced.

Happy Halloween!

-Edit-

Be sure to pull the +12 volt jumper you installed for the test on the A530. All devices should have only one clear path back to the source and there should be NO loops.

[jjans]

A few years ago, I had a problem with my A530's PSU. I replaced both A530's, and the A500's PSU's by running them both off a single 200 Watt ATX PSU.

I can open the PSU up and let you know how I wired it if you want - (can't remember exactly from memory - 10 years ago). I dp remember it wasn't very complicated, although I do think I was sober at the time....

[Damion]

Here are those jumper settings just for reference.


Format is: Jumper# Open Position/Closed Position/Factory Default


J1 MMU Enabled/MMU Disabled/Open

J2 Turbo OFF/Turbo On/Turbo Switch (this one connects to the case switch)

J3 Cache Enabled/Cache Disabled/Open

J4 Reserved/Reserved/Closed

J5 Reserved/Reserved/Open

J6 Reserved/Reserved/Closed

J7 Reserved/Reserved/Open

J8 SCSI ROM/ N/A /Open

J9 Non-Autoboot/HD Autoboot/Closed

J10 Reserved/Reserved/Open

J11 RAM Installed/No RAM Installed/Open

J13 1 MB SIMMs Installed/4 MB SIMMs Installed/Open

CN16 Reserved/Reserved/Open


Three Pin Jumper connectors:

CN11 Reserved/Reserved/Pins 2 & 3

CN18 Reserved/Reserved/Pins 1 & 2



cheers

Damion