Rectifier tubes flashing


I put two NOS TungSol 5U4GB rectifier tubes in my Cary SLI-50 integrated amplifier. They have great, truly vintage sound, but when I switch my amp from the standby mode into the operating mode, they flashe very bright for a second and then dull down to the normal soft orange glow. It does not affect the sound.

Is it a problem or it is just the characteristic trait of these tubes?

What is interesting, no such flashing occurs when I insert these rectifiers in Cary SLI-80 integrated amp which does not have a standby mode.

I would appreciate any explanation on this matter.

Best regards,

Alexander
transl
Power surge as caps charge up?
that would be my guess too, esp. if cap input filter into the PS.

-Ed