K8020 not working anymore

I bought the K8020 Valve Control Amplifier kit many years ago as a pre-amplifier, with two K8010 Valve Amplifier kits as finals.
After many years of perfect functioning the 8020 has stopped working (while the 8010s work fine).
I opened it and did not notice anything strange. I found out with the help of a tester, that the power was not flowing to the circuit board because the fuse in the power plug was burned, so I tried to change it. I could not find a 2.50A fuse like the original, so i put a 3.15 fuse, but nothing changed even if now the power is reaching the circuits and the transformer on the circuit board is now warming up. The valve don’t heat up and the leds and buttons on the front panel are dead.
I am not a technician and so I don’t know how to test all the components on the circuit board.
I need your help to solve this problem.
Thank you for your kind attention.

Hello Nencio68,

I think the best way is to bring it back to the shop, where You bought the K8020 for RMA REQUEST.
You can also ask for a Cost Estimate. Further You can add this topic as complaint.

Best regards,
Velleman Support.

I am in Italy. Actually I bought the kit online directly from you, along with the two K8010 kits, because there was no physical or online resellers which carried that product in catalogue.
But it was long time ago as I said: you were the only ones at that time to offer quality valve amplifier kits for a reasonable price. I think it was early years 2000. Sad you discontinued the products… they were just amazing.
And that’s why I want to try repair it, because even now I can’t find a pre with input selection like yours…