Amiga 600 not booting

[Mekanikal]

I have a question about my Amiga 600 not booting. I got this motherboard in a non working condition. It has no caps but looks very nice. Doesn't have any really bad leakage damage. The problem is that it doesn't boot. I get a video signal on rgb. Just a black screen and bright power led with no dimming and one caps lock flash.
I first suspected the u14 timer chip. Pin 3 first goes high then low as suspected. HLT and RST are high.
The cpu gets really hot to touch. Thats why I suspected a constant reset.
With diagrom I don't get any serial output. Do I have to have more caps soldered in place for this?
I have occasionally got a green screen. Now I am suspecting the cia chip by the disk drive port or maybe some via there.
Any suggestions?
Thanks for any help!

[project23]

I'm sure this is just a misunderstanding - but did you say it has no caps?

[Mark sealey]

Originally Posted by project23

I'm sure this is just a misunderstanding - but did you say it has no caps?

and its a non working motherboard ?

[Daedalus]

An Amiga doesn't strictly need the caps to boot - they just condition the supply rails and signals to make them more reliable and less stressful for the chips to deal with.

If the board's been reworked, check for shorts between the power rails. 5V to -12V or 5V to +12V are common enough on an A600, and can be brought about while attempting to replace capacitors. This happens with vias very close to some large resistors and diodes that are near Paula and use for the Paula and audio subsystem power supply - the vias are very close to some of the pads, and even a small amount of corrosion can cause a partial short. Without Paula you usually get a grey screen, and no serial output, but I guess a black screen might be possible too...

Is DiagROM flashing the power LED? Do you have any activity at all on the address or data bus?

[Mekanikal]

Originally Posted by Daedalus

An Amiga doesn't strictly need the caps to boot - they just condition the supply rails and signals to make them more reliable and less stressful for the chips to deal with.

If the board's been reworked, check for shorts between the power rails. 5V to -12V or 5V to +12V are common enough on an A600, and can be brought about while attempting to replace capacitors. This happens with vias very close to some large resistors and diodes that are near Paula and use for the Paula and audio subsystem power supply - the vias are very close to some of the pads, and even a small amount of corrosion can cause a partial short. Without Paula you usually get a grey screen, and no serial output, but I guess a black screen might be possible too...

Is DiagROM flashing the power LED? Do you have any activity at all on the address or data bus?

Diagrom is not flashing the power led.

I will check suspected vias but I am suspecting the cpu. It gets extremely hot in the middle. It hurts to touch it. Since RST and HLT seems fine it should not wait for anything. The keyboard flashes once so I guess it also gets a reset.

Somtimes I get magenta and green colors on screen. This also happens if I remove the rom chip.

I am really suspecting the cpu. Something is very strange there.

[Mekanikal]

Originally Posted by Mark sealey

and its a non working motherboard ?

Thats right. Non working and no caps. But that doesn't really matter.
The only cap that is needed is by the u14 chip.

[Mekanikal]

I have checked for shorts near paula but could not find anything. Checked som vias near u8 also. Could not find anything wrong.

[Mekanikal]

The problem with this machine was the cpu. It was dead. Replaced the cpu and now its working fine.