Vacuum tube ok or not?

[Simon123]

Hello!

I have gm5606 philips cro, and after looking ate the symphtoms i found one of these tubes is defective-left i think.
But i am not shure, it works just so there are voltages on the output, but it acts unstable, if i switch em aroun the other part of the circuit doesnt work.

So its little bit white on the top?

[G7PSK]

White on top usualy means that some air has leaked into the valve/tube. Check the filiment if not burnt out now it soon will be.

[AF6LJ]

As the poster above indicated the white on top indicates that gas is present in the tube.
Get another tube.

[SeanB]

It still has a good vacuum, but likely the heaters have lost emission and this means end of life. You can rejuvenate the heaters if you do not have another but best is to replace it with a NOS one.

[Simon123]

Ok, thanks ill proably buy new one.