I am working on a Stern SB100 Rev B out of a Nugent. I am only getting 2 of the 3 tones. I have been working through the techdose article and I'm pretty sure I can get it fixed from this. I am fortunate the sound generation (most of it) and the amp are verified working.
The issue I have is some extra components. It appears a jumper was replaced with a resistor with a couple of capacitors tied to it. These are at C50 and C52 and connect to U6 pin 10 which is the reset line. C50 is jumpered to the resistor on the back side of the board.
IMG_20171228_171851211 (resized).jpg
Clearly the board is resetting but I was having power issues on this machine that led to inconsistent booting. It's possible that someone put in these components to stabilize the line and get the board to reset.
I swapped in a different sdb and recrimped the power connectors on the rectifier board and the sdb and everything works great in that regard.
Should I remove this hack or leave it in? Maybe this relates to a service bulletin somewhere?
Thanks