Ac furnace help

Any heat and air guys on here is really need some technical help..went to work last night air condition blowing just fine son calls and say air conditioning stop..I get home this am check things over power is fine thermostat is fine so a buddy tells me the 240/24volt trans is gone I get 1 14.00 back home replace it and hear a pop it's gone..now I thought I had all the breakers off but didn't so that may have blown it..

Now this is what I have checked since ..if I turn my fan on manual it works just fine if I go out side to my unit and put the cover and push the spring control module the air conditioning comes on but it will not come on by the thermostat..any idea of what I need to check..should I just replace the transformer again with all the breakers off ..I mean I know I have to buy another one anyway but don't want to keep buying them if there is another problem..

Thanks for any and all help ..my grand kids had to stay in a 90 degree house last night that's not good lol there only 10months old and cranky lol ..