Converting PAL Amiga500 to NTSC

[SamuraiCrow]

The only reason you'd want to convert a PAL A500 to NTSC is to hook it to a TV set.  If you have a 1084S monitor and a Fat Agnus then you can switch modes with NTSCBoot option on Degrader.  Since most software runs in PAL mode it is actually preferred to have a PAL system even in the US.

[SamuraiCrow]

Correct.  Any RGB analog monitor with the proper PAL scan rate support will do.  The deal with the Commodore 1084S monitor is that it was designed for the Amiga and likely will come with the correct cable adapter for an Amiga 500.  (Be sure to ask if you see one on EBay.  The adapter cables can be hard to track down if the monitor doesn't come with one.)

Also, watch out for older 1084 monitors that have a round connector on the back.  These had a problem with the heat causing the solder to "putty" (meaning the connections on the 1084 system board degrade and would cost so much to repair that you'd be better off getting a different model).

[SamuraiCrow]

You only need to worry about the colorburst signal on an A600/1200 since they have the composite/TV tuner signal built in.  On an A500 you'd only need to worry about setting a bit in the startup-sequence and getting an appropriate A520 TV/composite encoder.

Regarding the solder joints on the older 1084 monitors, the main cost isn't the materials, it's the time.  You not only have to replace the old solder but you have to scrape the connections off and, as was mentioned earlier, there are some electrocution hazards involved in working with monitors.