Help troubleshooting Dual Gate Slew

[dstrength]

I'm troubleshooting a Dual Gated Slew module, and both sections 1 and 2 are exhibiting the same behavior:

1) In LIN mode, the slew time is very short even at values of 1M on P1.

2) In LOG Mode, the slew time works normal, but the rise / fall direction switch doesn't seem to affect the slew. That is, I get slew in both directions all of the time. (The direction seems to work in LIN mode, but it's hard to tell since the slew time is so short.)

Now, I've noticed that I used BF245B instead of BF245C. I realize the B has a lower gate-source voltage range and a lower zero-gate-voltage drain current than C. But, I'm not sure how / if I can adjust the circuit to utilize the BF245B...or if it is even related to the problem.

Any ideas or suggestions?

[yusynth]

Since they share the same cap it is normal that the LIN slew is faster than the EXP slew.
The RISE/FALL switch definitely should give a different behaviour, check that your diodes are not dead (short-cut) and correctly polarized.