Goldstar es una marca un poco viejita, fue rebautizada a LG hace ya mucho tiempo. Lo mas probable es que el TV haya sido reconvertido a PAL y no se pueda cambiar de norma.
En todo caso, proba con el control remoto de la TV para ver si aparece algun menu en pantalla que permita hacer el cambio de PAL a NTSC.
Te ofrezco, si te interesa, un modulador A520 PAL gratis, solo te pediria que me pagues el costo de envio a Uruguay que es menor a diez dolares americanos, tendria que averiguar cuanto exactamente.
In English:
Goldstar is a little bit old brandname, it was renamed LG long ago. The most probable thing is that the TV has been reconverted to PAL and you cant change the standart.
Anyway, you should try with the remote control of the TV to see if some kind of on screen menu appears that allows you to change from PAL to NTSC.
I am offering you, if you are interested, an A520 PAL modulator for free, i will only ask you that you pay the shipping cost to Uruguay that is less than 10 USD, that i will eventually have find out the exact amount.