Two additional modifications for the PMC servo (S1503974, modified TTFSS)

- Removed R4 on the TTFSS Slow board (D0901895) to gain the full +-10V range for the SLOW output, which will be used as an output offset (connecting it to the FAST EXC point).
- Disconnected the High Voltage Opamp PA98A (U6 on the TTFSS:HV/Inteface board D0901893). The opamp is socketed, so I just pulled it out of its socket and mounted it to the back panel for possible future use. This takes the HV path out of action, an we don:t have to worry about saturations in that path.