You were not running the output IC at 28V, you were running it at 56V (+28 0 -28 gives 56V total).
Why it has blown again after changing to a 12 0 12 VAC transformer I have no idea, but as I said before internet fault diagnosis can only be as good as the info provided.
Please measure the voltage on the output IC power supply pins. You are assuming that your 12 0 12 VAC transformer is what it says on the label and as an old engineer and mentor told me when I was an apprentice "Never assume!"
ballfire wrote:should i change it to 4 ohms
No, running a 4 ohms speaker will stress the output amplifier more than 8 ohms.
There is the possibility that there might be a a fault with your speaker which is putting too much load on your amplifier when you turn the volume up (voice coil shorting to the magnet).
One thing at a time, remove the now faulty IC and measure the voltage on each of the supply pin pads.
thanks man for the reply...whatever you are sir thanks for the great advice..
you know im debugging repeatedly this amp for 1 year then it never return back the old mojo tone of this amp..
before it broke ..i like this amp very much because theres something in it makes my diy pedals really roar mostly distortion..
last year it just suddenly busted up and became tingy output..im frustrated of this amp..i try everything in it to fix it but..i dont know what the hell happening inside of it ive check the resistor and everything..everything..
now last week i decided to change the transformer to 12-0-12 as advice..and change the power amp ic to TDA2040 because the former chip is not available..the amp power up and the the mojo tone came back im very glad it returned..but last tuesday night when im playing
the problem returned..damned fuck ..
last night because im really furious now what supposed to do i change the power amp ic with new TDA2050 and it work!!!! and the speaker i install it with new one a 100 watts 8 ohms..because theres no available 30 watts on our place..the amp works the mojo tone again back atleast.....
this morning when i plugged to see if its okey ..im shocked there a loud hum when i plugged the cable to my guitar on ti..but theres a signal output when im strumming my guitar ..when i touch the cable plug to the input it disappear..damn i think it has a jinx or something...
any advice sir....