Sonograph SA-250

I need to replace the fuses for 1 channel on my SA-250. I think you also have to open 2 screws on the top back that are attached to the heat fins. Does anyone know what type of screws these are? I have tried the hex 2.5 mm, but that does not work either.

Thanks for the help
If they are Hex (Allen) type screws, they come in both metric and SAE. Also, look at them very closely. Use a magnifying glass if you have to. On screws that small, its very easy to mistake hex for torx.
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