That's a good test, thanks for taking the risk to check out the relay effect.
Concerning the hybrid board i have not heard anything from NP.
i have been searching to identify the little 5-pin chip and found the Ricoh site helpful for searching by package type. Now i'm wondering if it might just be a little op amp such as the NJU7026 in which pin 1 the non-inverting input is just not being used, as it seems to have no connection anywhere?Ricoh NJU7026
the output on pin 4 of this chip must alternate between the two supply voltages at the same time and in the opposite polarity (180 degrees phase diff) to the output of the power transformer, such that when the A&D control lines go Hi, B&C go Lo; and vice versa, in order to route an alternating inverted input thru the signal transformer. What kind of device does that--what is that thang?