how can i fix my fender frontman 15 r amplifier ?

the problem is when the volume is turned up even by the smallest amount its like its at full volume with howling and feedback, and if i select the reverb i get a ticking sound, this does not seem to happen when i have the headphones plugged in, ive removed the 50k main volume pot and cheacked it, seems fine , also there are 2 ics i cant see the number of, the ones i reconize are the TDA 2050 & TLO72 I THINK ITS SOMETHING LIKE 85033L, can you confirm this.
also is the transistor a BG 35, OR A J111, can you HELP

JOHN