Silvertone roundie focus issue

[timmy]

well here goes yet another thing going on here with this set, im sure this 21fb is tired but what its doing is after turning it on the picture appears focused for about 5 seconds then the picture is totally out of focus for about 3 minutes then it clears up nice. its got the clone ctc15 chassis so im thinking the crt, focus rectifier, otherwise i dont know. the flyback is new so it wont be that. any ideas would help, thanks