Hp91 with very dim display

[James Linder]

I have 2 97’s and 1 92 that work fine too, so unfamiliar with the display issue. Printer makes noise and advances paper but no characters appear on paper. I will tackle that issue after fixing the display issue first. Based on what you have advised I believe that I should check power supply to see if output Voltage is correct. Can you tell me what components make up the power supply? A picture would be best of course. Thanks