Hi, I have been away from the forum due to health issues and just had a quick read of your post. I originally posted that diode cap solution on the M4 IGN line and although this does solve some problems related to some installations of the M4 it does not solve all problems.
In fairness to the M4, I have recently found that the cycling problem while resuming from Suspend to Ram is actually a Motherboard design problem.
Firstly, the mother board will always work perfectly when resuming from Hibernate. The problem is only apparent when resuming from STR (suspend to ram) due to +5v standby rail.
In my case, the problem is intermittent and the unit can resume from STR in 2 seconds a dozen times throughout the day and work perfectly every time, then for no apparent reason it would cycle on/off trying to boot. As you noted, the only way to get it to boot was to remove power from the PSU for a few seconds.
From tests I recently carried out it appears that the problem is caused in two ways.
The initial failure to resume from STR is caused by the PSU thinking there is a problem with the 12v power input. It appears that most PSU’s will drop the +5 standby rail if they detect a problem, this is chicken and egg situation though as the MB will signal power good failure if the various supply rails don’t come up in a pre programmed time/sequence. This in turn drops the +5v Standby and in either case you have the MB failing resume and trying to reboot.
Changing my current MB for a newer MB from the same maker completely solved the rebooting cycle issue. Changing the PSU has no affect on this constant rebooting loop. It always follows the MB (BTW, latest Bios firmware)
I carried out further tests into the cause of the initial failure to return from STR. In other words, why does the +5v standby drop as soon as the PSU signals the MB to start?
The M4 was actually much better that some of the other 12v PSU units I tried.
In some cases putting a 40,000uf cap across the +12 supply input would stop the JAYCAR PSU/ MB combination from resuming from STR almost every time. It appears that in this case the Generic Switching Convertor controller does not like a very stiff +12 input and drops +5v standby causing the MB to fail on resume from STR. It should then do a cold reboot; however my original MB would lock in a power up cycle.
The newer MB correctly reboots after the first failure.
The M4 fails with the right combination of input voltage AND voltage change just as it powers on, and will drop the +5v standby rail every so often. Once again it may be a timing issue between the MB and the PSU causing the MB to signal Bad Power. The M4 allows you to change PSU rail timing for all supply rails, however I had no interest in going down that road.
I now use Hibernate, its fast enough for me and the CAR PC has been absolutely faultless in operation. The M4 performs perfectly and after rebuilding the complete system into a larger case and combining the PSU, MB, DAB radio and Remote volume control unit into the same large case all audio noise and RF noise has finally been eliminated (exorcized).
Hope this is of some help.