I am trying to collect diagnostic data from Mark I system. Do you know of anywhere I can obtain MKI backsheets?
The MK I backsheets include detailed circuit diagrams of the SPEEDTRONIC analog control cards. They are (or at least were when I worked for GE) considered proprietary information, and as such were not available to non-GE employees. The elementary diagrams provided with the equipment showed interconnections among the control cards and their connections to the physical analog I/O and discrete logic I/O.
You did not say what kind of diagnostic data you want to collect.
The Mark I (and Mark II) SPEEDTRONIC cards do not provide self diagnostic information for the control system. They did have some alarm outputs that were connected to light-box type annunciators. The analog control signals were generally not made available for external monitoring. Some customers asked for a limited number of these, and isolator cards that provided 4-20 ma signals were provided for a not so small fee. You could not physically accommodate many of these cards in the Mark I control card racks - only 4 signals (I think) per isolator card, each card occupying 1 slot in the rack.
Back in the early 1980's GE offered a SCADA type monitoring system that included what was essentially a large A to D converter for the analog signals, the digital side of which was connected to a minicomputer (PDP 11 at first, later on VAX 750), but this was not a big seller because not many end users could justify spending the money on it. This was only used on Mark II, to my knowledge, not Mark I controls. It was called DATATRONIC, a name also used for a Mark IV vintage control system, which also had a short lifespan.
At this point, if you really need to import data from this turbine (or turbines) I suspect it would be a lot more cost effective to replace the Mark I control with a Mark VIe simplex control.
We had 2 Mark 1 systems and a Mark 2 AMS system. We are just replacing the last system now after 39 years of very reliable service on the Mark 1's and 32 years on the Mark 2. We hooked up our own signal isolator modules years ago to monitor critical signals continuously and available for viewing on a PI system. All valve positions, Load Set, Load Ref, EL, Speed, Speed Error, Power Supply Voltages, and Oscillator outputs were monitored with 1 second scan times. If something went wrong, usually the monitored signals would point to the problem. We also had a 16 channel high speed recorder available to monitor anything you wanted to diagnose noise problems etc.
GE provided us with the detailed schematics that showed all board mounted components. Integrated circuits were shown simplified. I thought all customers got these prints, I know that other utilities have also been provided with these documents.