Spice Calculator - dim display - HP38C

[teenix]

I found a supply buried in a box and I marked the 4 components on the attached image.

Hard to say what might die in the supply, caps and transistors are probably the main culprits.

I think my supply is from an E model, so not sure about the brown "thingy"

If you have a spare supply, that would be the easiest to replace and try out.

Also, check pin #8 of the large CPU chip, it is the constant current input for the displays. If it is an unsoldered version, it may not be contacting the flexible circuit properly. You might notice some changes in brightness if you apply some pressure around this area while turned on. The current also passes through the power supply ribbon connector (pin nearest the center of the board) so this might not be connecting properly as well.

cheers

Tony