A few years ago I bought for peanuts Cambridge Audio DVD89 player, because I've found out that it can be flashed with firmware allowing SACD-R reading. It's in excellent condition except faded VFD display, it was probably left powered on in standby for too long.

Anyway, I've read and read internet old wise man on VFDs (these are tubes actually!) and when I understood the principles I've decided to try to restore this faded display using 9V battery.
In this particular case it was not about dried capacitor or fried diode in filament power supply, as service diagrams show that power comes from dedicated transformer secondary wiring.

Filament has to be heated up to burn all the deposits from chemical reactions with impurities that took place during past 20 yrs.
The easiest way is to provide more than regular voltage and use current to burn the nasties.

REMEMBER to disconnect the display! You don't want 9V wandering around PCBs of your device!
Also, do not try this DIY if you did not understood this description!

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