1008C incorrect amplitude

OASJ2YSeeEhBQo1

Hi,
    I'm with a 1008C oscilloscope with the following problem:
    The device is showing an incorrect value for the amplitude of a      signal, for example, the 2Vpp test signal shows only about 400mV.      The shape of the signal looks ok, just the amplitude is wrong. It is not a problem with the      compensation output, it's working fine. I tested all inputs      with other signals and the problem was the same. The software      settings are correct too.
  

    I know it's hard to guess without more details but, do you have      any idea of what can cause this kind of problem? Is there any      procedure that I can do to test it further?
   
    I found some old threads in the forum with reports of the same      issue but, there is no more information in there:
https://www.eediscuss.com/forum.php?mod=viewthread&tid=9392 (see point 1) or another one
https://www.eediscuss.com/forum.php?mod=viewthread&tid=15121

thx

OASJ2YSeeEhBQo1

All channels have the same problem.

OASJ2YSeeEhBQo1

I have already sent an email to Amy before post here in the forum but I got no reply. I will send you a message.

Thx.