Re: Replacement part for IC4 #fst3253


M0RON
 

Hi Alan, 
Definitely the chip. 
Qlg1 was attached to a u3s and was working fine for weeks. Then it suddenly stopped, u3s still running, 5v very well regulated supply. I initially thought it was the rf chip but I probed the input to the chip from the rf chip and it was definitely receiving signals from the rf chip, the output however was a constant 2.34v or something around there on both outputs pins 3 and 8. Consequently pins 4,5,12 and 13 were fed a constant voltage which meant that the green led was constantly on and the yellow led never lit. Removed chip without damaging the board, soldered in a socket, replacement chip and all was good again and still is.
No voltage spike or incorrect voltage applied, it just failed, must have been an internal fault,  I destroyed the chip to remove it from board so didn't check it further. Just one of those unexplained failures, though I must say that I haven't had any other IC's from anything else I've built fail so one chip isn't bad and nothing else was damaged. 
Andy
--
The universe is made up of Protons, Neutrons, Electrons but contains only one M0RON.

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