I just worked on a CT-26v with very similar symptoms.
The preamp would not power on either from the remote or directly. No lights. Even the red standby LED would not come on. Cosmetically the preamp was in mint condition with no signs of abuse. All 3 1A/125V fuses inside were OK.
When the standby LED does not light up, suspect a problem in the standby power supply - which luckily has very few components. I verified the relay worked and was OK. The 3-pin voltage regulator and the 2 transistors (2Sc1740) were good.
The culprit: Diode D551 across the relay was short. I replaced it with a $0.25 1N4148 from my junk box - the relay clicks in, all lights work on the display and the preamp sounds wonderful
The diode was probably a sub standard equivalent from the Chinese mass production assembly line.
Hope this post helps someone resolve a similar issue in future and keep the Carvers running!