Hi.

I'm working on a Chroma Polaris, and it seems to have a faulty resonance issue.

By the time the slider is at the half way mark I'm on full resonance, and I only seem to have 4 steps. This is same for all voices.
Being a tech, I've been probing around trying to see what's going on.

If I look at the signals coming off Z49, I'm not getting anything on Pin 3 which is the ResA line.
The input (17) to this looks fine.
I've swapped the chip and still no change. If I lift the leg and probe I still get nothing on the scope, so It's not being pulled down.

If I look at the output of Z80 (pin 6) it appears to be stuck high. and tracing back, the (Not) PCS6 line is static.

I may be looking in the wrong areas, and barking up the wrong tree.

Anyone else had this issue, and solved it?

Any pointers would be most helpful.