a stern seawitch sound problem

[AlanJ]

As soon as you power on a loud constant pitched noise. game boots ok but the noise continues. starting a game stops it and all sounds are ok (i think), it’s then fine between games.

I remember seeing this on another stern, i’ve checked continuity in the ribbons from mpu to the sound board.

 

[stevebm1]

has the 7402 chip gone bad?

 

[Arv]

Have you had the ribbon off between the sound board and the mpu?

I'm sure I had this on mine when I miss aligned it by one pin.

 

[stevebm1]

I think the 7475's can fail as well,and cause the squealing issue

 

[AlanJ]

has the 7402 chip gone bad?

i’ll test

Have you had the ribbon off between the sound board and the mpu?

I'm sure I had this on mine when I miss aligned it by one pin.

it’s a loan game from EC so possibly. i did replace and pretty sure was on ok. i will double check

I think the 7475's can fail as well,and cause the squealing issue

this isn’t a squeal, just a constant tone.

 

[AlanJ]

ribbon cable all on correctly and pin 34. on sound card not connected to mpu pin 34 (as advised by pinwiki). all looks good

it’s alltek mpu, so i cleared the memory as i know that can cause sound issues.