Amiga 500 intermittently reboots for no reason!

[DrDekker]

Make sure you've got the sound hooked up to your TV or WHY and listen out for 'machine gun' style interference (technical term - ahem).  If you hear such noises - it'll probably caused by a faulty PSU.

[DrDekker]

circlip wrote:
 If you meant for me to use the A520 Modulator, I haven't got the right cable for the RF OUT, I'm only able to use the A/V ports.

The audio ports are just fine.  Also check the keyboard connector on the motherboard - a bad connection here can sometimes cause random reboots.

Another cause can be the keyboard controller chip located on the keyboard.  On early models the chip is socketed (red LED for floppy drive?) - on later models (yellow/orange LED - e.g. A500+) the chip is soldered directly.  If it's the former - just lever the chip out a little and press it back home.  Since the fault is random (ish), it could be just a poor connection.  If the capslock light flashes in a particular sequence it usually indicates there's a mainboard fault or the keyboard controller chip has gone west.
 

[DrDekker]

Just remembered - I once had an A500 (a very long time ago) that had the same problem.

It took me quite a time to find the cause.

The problem ended up being a dying Denise.  Once replaced, it was rock solid.

[DrDekker]

As far as I know there isn't any means of testing it, but I found out it was the problem by pressing down on the chip when the A500 was switched on and watched out for the reboots.  Sometimes the Amiga would reboot and other times it would stay on for ages.  I then thought it was just a bad connection, but the problem didn't go away until I replaced the Denise.  The original chip must have had a dodgy leg or something.  It's worth a ago replacing the Denise as she's a pretty inexpensive old girl. :-D