HT-5R Combo: How to reveal the circuit board??

[darkestwinter]

So my HT-5R combo suddenly stopped working. At first I thought it's the tubes but after a quick research the issue seems to be with the R38/39 resistors.
I'd like to check the circuit board but I can't figure out how to reveal it, as the top wooden part of the amp appears to be glued to the chassis.
Any help would be appreciated.

[Uffingdon]

Have you tried removing the little black screws on the back panel, they maybe what's holding the chassis to the panel?

[darkestwinter]

I tried removing them now but as I suspected these screws are too short and their sole purpose is to support the metallic diagram of the inputs/outputs.

[thephantum]

If you've removed the four machine screws holding the chassis to the panel, they are just stuck together. They will come apart. It just takes some patience and some prying.

[zoziano]

In this case, if i have to change the power tube with an other one different from stock one, where i have to control the mV values in order to bias it?? Only between cathode R33 and ground (Plate)?