1991 S10 Blazer

Hello, the Speedo on my '91 S10 Blazer's digital instrument panel wont work properly(wont show up). When we got the car, it had been sitting for a couple years and the speedo worked when we had gotten it a couple days ago. Now, the Speedo wont show up(screen's blank) unless you hit the top of the dash, and it comes on for a couple seconds, but then it turns back off.

I had replaced all of the bulbs, but the problem still pursues.

From what I've heard, the Circuit Boards have issues with solder connections cracking over time, but I personally couldn't find any cracked connections on the main board. I have heard that the smaller board, which is attached to the main board might be the issue. I'm terrible at soldering and still don't have the right equipment to work on it, so I don't want to take that board off, with the possibility that it might not even be the issue.

Anyone have opinions on what it might be? I'm afraid I might have to send it to get repaired, or even buy another board.