How to open a HT-5 Metal Head?

[Prins]

Hello guys. I´ve just I bought a HT-5 Metal head and I have 3 pre12ax7 i´d like to test (jj ecc83s, Psvane and Spax7 MESA). My doubt is: Only those 4 rear panel screws must be unscrewed or some more? i´ve tried unscrewing these 4 screws and pull but it looks like the tolex is firmly glued or something else is firmly holding the back cover.

[thephantum]

It's not glued. The tolex just sticks together. The panel will come off, it just takes some patience.

[Prins]

It's not glued. The tolex just sticks together. The panel will come off, it just takes some patience.

Thanks, i will use more strength to pull and more patience. Maybe 2 thin screwdrivers in left and right screw holes will help. Cos not many places to grab and pull the cover.