Hi Yan, thanks for your post.
I’m afraid that your VC6 has a serious power supply problem. I’m afraid I don’t have the circuit diagram for the VC6, but it is very similar to the VC3 and if you would like to drop me an email at ted@tfpro.com I will email you a copy of this…. But I would suggest that the fix is not simple. Once the power supply fails on these units, it’s often the case that it takes out most of the integrated circuits, so the fix could be expensive.
I have an arrangement where I service all old equipment of my design, for a fixed fee of £25 plus the cost of returning it.
I can’t guarantee to fix this one, but if you like I will try. 