First time this year I decided to hook up an A500 that I bought 2nd hand last year, with an A590 with original Western Digital XT hd. So I connected the two power supplies to the A500 and A590 and turned them both on ... but the A590 did not boot and the A500 gave me first a green screen and then a yellow screen. After trying several times to reconnect the A590, thinking it might not have been pushed hard enough into the A500 I decided that the connection itself was not the issue. So I tried to boot it all up without the power supply connected to the A590, thinking the power supply might be the problem, and to reduce power consumption I disconnected the Western Digital XT drive, both the data and power cable, so the A590 was supposed to boot without hd ... still the same problem, yellow or green boot screen colour. The A500 works perfectly without A590, no problem at all !!
Decided to look at The Big Book to see whether the jumpers at the back of the A590 were set correctly but they are all set to 1, so that is not the problem. I may have plenty of Amiga's at home but I am still not technical minded enough to sort this out so that's why I am asking for advice

I know it looks like the A590 itself is busted and ready for the trashbin but it would be a shame afterwards to find out that it was so easy to fix ...