Amiga 1000 + 1083s Monitor (interference with floppy drive)

[rjd324]

When the monitor is unplugged the A1000 goes on to read floppy disks fine. When the monitor is turned on I get failing reads of floppy disks.


The monitor sits on top of the A1000. The A1000 has the shield installed. All screws are inserted, but I will double check.


In the meantime is this just electrical interference. Can someone shed some light?

___

Update: In the meantime I can move the monitor so that it is further to the left side of the case and it then works. I was thinking that the weight could be having an impact, but surely note since that does not explain how the DF0 works when the monitor is switched off.

[turrican9]

cold solderjoint on the +5v rail somewhere that causes the +5v to drop enough when the monitor is on for the floppy drive to fail?

[lord of time]

Originally Posted by turrican9

cold solderjoint on the +5v rail somewhere that causes the +5v to drop enough when the monitor is on for the floppy drive to fail?

how does that even make sense? the monitor and floppy are powered by 2 seperate power sources! and even if they wasnt a CRT monitor uses higher levels than +5v!!!

[shaf]

is the shield on in the A1000 around the FDD, this sounds like a case of RF interference which i have never seen with an A1000 and A1080 Monitor, maybe the A1083 is not shielded as well. But this is only an assumption, i would need to see the A1083 Schematics.

[hooverphonique]

Interference should be easy to rule out/verify by moving the monitor away from the A1000 chassis.

[turrican9]

Originally Posted by lord of time

how does that even make sense? the monitor and floppy are powered by 2 seperate power sources! and even if they wasnt a CRT monitor uses higher levels than +5v!!!

RGB uses +5v from the Amiga from pin 23

When the monitor switches on the +5v is used to trigger the RGB as far as I understand. And if there was a cracked solderjoint on the Amigas +5v feeding somwhere that extra small load on the +5v might be enough to make the floppy drive fail. Just a guess. An easy test would be to instead connect the monitor to the composite output. See if the floppy drive works then

Edit: It is not uncommon to see the screen dims very ligthly as the floppy drive clicks (looking for disk). I am pretty sure this is because the floppy drive puts a load on the +5v and when it clicks there is a very small voltage drop on the +5v line. Which in turn makes the screen dim very lightly as the floppy drive clicks. Because RGB is triggered from pin 23 +5v on the RGB port.