Choplifter has no sound.
Checking all the capacitors (visually at first) --> seem ok.
Checking the amps --> seem ok.
Checking both sn76489an -->seem ok.
"Seem ok" of course only at first sight and checking is limited with ics not being out of the pcb, but before I begin to desolder I want to go through this.
Looking at the schematics shows that there is a MUTE signal coming out of 8255 IC146 (pin 14).
Pin 14 IC146 goes to pin 5 IC147 which negates to pin 6 and goes to pin 7 IC151, a ULN2003 which gives the end result MUTE (active low).
And since MUTE is always low there is no sound.
Checking 74LS04 IC147 shows that it is ok, so ULN2003 IC151 is most likely the source for the error.
Desoldering ULN2003 IC151 and testing shows that it is faulty.
Replacing with a new one brings back sound. Job done.
Checking all the capacitors (visually at first) --> seem ok.
Checking the amps --> seem ok.
Checking both sn76489an -->seem ok.
"Seem ok" of course only at first sight and checking is limited with ics not being out of the pcb, but before I begin to desolder I want to go through this.
Looking at the schematics shows that there is a MUTE signal coming out of 8255 IC146 (pin 14).
Pin 14 IC146 goes to pin 5 IC147 which negates to pin 6 and goes to pin 7 IC151, a ULN2003 which gives the end result MUTE (active low).
And since MUTE is always low there is no sound.
Checking 74LS04 IC147 shows that it is ok, so ULN2003 IC151 is most likely the source for the error.
Desoldering ULN2003 IC151 and testing shows that it is faulty.
Replacing with a new one brings back sound. Job done.
