Amiga A500 fails to start up when connected to 1084S monitor

[PompeyPaul]

I have an oldish Amiga which has a couple of issues.

The most pressing is that if I boot the Amiga with the TV Modulator in then everything is fine. If I boot without anything in the RGB out that the Amiga boots fine.

However if I boot with the 1084s monitor connected then I get a flashing power light, it fails to boot, and the monitor shows white which looks like the synch hasn't worked.

If I boot the amiga, without the monitor connected, then connect the monitor then everything works fine.

With everything working fine, if I hold ctrl Amiga Amiga, to boot again then I get a guru meditation error. 15000002. Decyphering this suggests it's a timer device, which also matches the garbled output on the monitor. Looking at this website I have it decrypted as:

15000002 Bad Supply

Has anyone seen this before? I'm presuming it's a case of getting to the motherboard, pulling the chips out, cleaning with isopropyl and then ensuring all of the chips are back in solidly ?

Is it worth replacing the power supply? I'm unsure how the timings work on the hardware.

As an aside I've found the Amiga to struggle reading discs. I've dismantled the drive, cleaned heads & motor etc, but it still seems very intermittent. I'm not sure if the disc issues, and the timing are related? I'm not 100% sure on the disc issue because I bought a job lot of 200 discs and have found very few boot. It could be the discs, it could be the drive. When I do find a disc that boots it seems to boot cleanly and without much noise from the drive so I think the discs are bad, and the disc drive is good but unsure. I've noted that some discs that boot one time, don't boot at others, but I believe this is because they are essentially analogue storage.

[nikosidis]

The disc problem can be timing related. You can try replacing the capacitors on the floppy drive.
If the discs are no brand I often seen they go bad. Branded discs are often more reliable.
It seams this can also be a CIA chip problem. Try to swap them. It is the same chips. That can some times solve it.

The RGB out problem seams strange. I have no idea. Try to take out Angus and as you already mentioned clean the socket chips. A recap of the mobo can also be smart. Check all traces and look for bad, cracked solder joints.

[Toni Wilen]

It sounds like Amiga detects genlock which also happens if there is enough load on Amiga sync lines (sync lines are bi-directional). This is common with some VGA monitors when not using buffered interface.

If this happens without genlock, system will crash because internal hsync/vsync pulses are not generated anymore, CIA TOD counters stop (which causes that guru you mentioned. It mentions PSU because big box Amigas use power supply tick in place of VSYNC)

Possibly as simple as bad cable, for example short in composite sync line.