A Mysterious Hardware Issue

[eva]

Hi!

This is a rather historic request rather than something recent... I used to have this A500 quite a while ago and it had this very weird issue of rebooting itself mysteriously during usage. It had a 512KB expansion inside it I remember... However, nobody was able to solve the mysterious issue of the reboots...

The reboots did not seem to trigger in a pattern - even if the Amiga got hot, running a game, working in Workbench, it would not matter... Randomly, it just reset itself. I do not remember any screen color after the reset and it was not a guru meditation. Just like that... Poof... And we are resetting as if you pressed the three finger salute. Something else I remember is that it sometimes went into a reboot frenzy. So, it rebooted itself once. Then again, then again... A few times, till it came back to its senses.

Even if I powered-off the Amiga and powered back on during the reboot frenzy, it did not seem to make the slightest difference. I also tried at some point replacing the power brick but that did not make any difference either.

It must have been a hardware issue...

Alas, I have no access anymore to that machine but out of curiosity I wonder what could have been busted... It's like the Nemesis of my Amiga experience! It was taken to some experts, they could not figure it out, brought back, etc... Perhaps someone had some similar experience, or perhaps it is a known issue? Any speculation is welcome!

Thanks!

[BigFan]

Sounds like one or more 'shaky' capacitors to me, either on mobo or in power supply. If voltage does not raise within specific time or drops due to aged electrolyte that specific power trace will fail. As the caps can't reload in time, the reboot frenzy happens.
Reset does not help then.

Sometimes machine has to cool down or to warm up, depending on what state the caps are toggling, high or low voltage.

[Toni Wilen]

Does it still happen if you disconnect keyboard? (Keyboard can generate hardware reset signal)

[eva]

Originally Posted by BigFan

Sounds like one or more 'shaky' capacitors to me, either on mobo or in power supply. If voltage does not raise within specific time or drops due to aged electrolyte that specific power trace will fail. As the caps can't reload in time, the reboot frenzy happens.
Reset does not help then.

Sometimes machine has to cool down or to warm up, depending on what state the caps are toggling, high or low voltage.

Ah yeah, so a capacitor problem? I have heard about bad capacitors since I have (re)-joined the Amiga community. What is up with these capacitors, again, tangential to the OP? I mean how come this sort of thing does not happen to PCs - or perhaps it does but we just chuck out the hardware soon enough not to notice?

The frenzy used to happen sometimes. Other times, you were just writing a document and suddenly the Amiga rebooted. Either one reboot or multiple ones. What was nasty was that it could not be traced to something specific. So, it could very well happen on a cold fresh start the next day, or it could also happen after prolonged use.

I am planning to replace my capacitors on my A1200 - I have found a local service that will do it for me. I am thinking perhaps there are some more expensive capacitors that last longer? I have seen someone selling some capacitors (from France, I think) for the Amiga but they look identical to the ones already installed on the motherboard. Are there not some "long-lasting alternatives", particularly with more recent developments in electrical engineering?

Originally Posted by Toni Wilen

Does it still happen if you disconnect keyboard? (Keyboard can generate hardware reset signal)

Never tried... Or perhaps the people I sent it to did. I can never tell for sure. The machine is long gone though, hence the more "historical" question. It is one of those mystery things that will haunt me on my dying bed. Why did the A500 reboot by itself?

[Fingerlickin_B]

Originally Posted by eva

I mean how come this sort of thing does not happen to PCs - or perhaps it does but we just chuck out the hardware soon enough not to notice?

It does & yes, more often than not, we do.

PZ.

[hooverphonique]

Originally Posted by eva

I mean how come this sort of thing does not happen to PCs - or perhaps it does but we just chuck out the hardware soon enough not to notice?

the previous mobo in my desktop pc had this problem and I exchanged the electrolytic caps myself, which gave it another 6 or 7 years of life.. was chucked earlier this year due to a different problem, though..