It's possible to convert the 400 to output composite.
As it only cost you 35 sovs you may as well try it and it's useless to you as it is anyway.
You may have to Google a bit but it seems people have managed it:http://atariage.com/forums/topic/209136 ... 400/page-3
1977 VCS Heavy Sixxer (Boxed)
1990 Atari 1040STE, 4MB, UltraSatan, TOS 2.06, TT Touch -> Atari SC1435 Colour CRT Monitor
1991 Atari TT030, 2/16MB, Int 8GB Gigafile SCSI2CF, TOS 3.06, CaTTamaran Accelerator -> Atari TTM195 19" Mono CRT Monitor
1993 Atari Falcon030, 14MB, Int 4GB IDE2SD, TOS 4.04 -> Atari PTC1426 Color CRT Monitor
Amiga, Mac, DOS, Newton, SGI, Sun, NeXTStation and more!