Your display is being under-volted, which can cause certain areas to appear dim and shaded. -98v is definitely low, 68v is a little low, and 5v is a little low although this shouldn't make it dim. An older display can be dimmer to begin with due to age, and add low voltage on top of that and you definitely will see dim portions at certain times.
Try re-seating the connectors and re-check the voltages. If that helps, you may need to clean connections or maybe re-pin some connectors. If that doesn't make a difference, check voltages directly on the power supply. Pinrepair.com will tell you everything you need to know.
I'm guessing that the problem lies with either the connector on the DMD, or the connector on the power supply, or both. Since all the voltages are a little on the low side, it makes me think the problem is a connector rather than the high voltage portion of the power supply.
I'm betting that after you get the low -98v and 68v solved, you'll have a nice looking DMD.