Topic of the day: Superdrives and thier DONTs. — #18

Post #18 by iMac600

Source Forum	68kMLA
Category	Troubleshooting
Post Date	Sat, 12 Dec 2009 - 18:05
Original URL	https://68kmla.org/bb/threads/topic-of-the-day-superdrives-and-thier-donts.19254/

Post

I'm fairly certain that "whoop-whoop-whoop" and "flup-flup-flup" or "whup-whup-whup" are all best efforts at describing the same thing: Power supply in self-protect mode. A current overload triggers it (an overvoltage will also indirectly trigger it), so anything that pulls too much current from the supply can make this happen.

Spot on. The power supply goes into self-protect mode, where it constantly attempts to seemingly restart the power flow. The "whoop" or "flup" sound (both of these sounds are correct) is the floppy disk drive attempting to start up, being cut short, attempting to start again and so forth, all in time with the power supply starting and restarting. If the FDD is disconnected, in this case the machine powered up just fine, but on machines with deeper issues you'll only hear the PSU whistling in time with where the "flup" noise would normally occur.

It's caused by one of three things, unfortunately all three are pretty broad headings and require some narrowing down to determine the direct source of the issue.

1. Something is pulling too much power from the electrical feed. This could be any component except the analog board drawing too much current, such as another component with an internal short.

2. The power supply can not keep up with the demands of the attached components. This often occurs when the power supply is worn and needs replacement components, mostly capacitors.

3. There is a problem routing power around the power supply. Think of a cracked solder joint on a flyback transformer for example, the electricity can not pass through a broken joint and therefore the power is not reaching its destination. The power supply goes into self-protect mode as a result.

It sounds like 1 or 2 are the most likely in your case, but it requires some knowledge of the superdrive to narrow it down. Additionally knowing which component let out the smoke would also be a handy hint. I can only deal with issues 2 and 3 for the most part, but everyone here already has it covered.