How to tell vacuum tube is gone bad??

chunki84

Member
Messages
5
I recently purchased primaluna prologue 3 and I connect with dynaudio bm6a.

First I saw is lights of three vacuum tubes are dim and

other lights of three vacuum tubes are bright.

Among 6, 1 of vacuum tube has little soot on wall.


When I connect output-2 with bm6a speaker (active speaker), the volume is very low even I tune max volume.

When I connect output-1 with the speaker, the volume is loud enough with 1/3 of preamp volume.


Are these symptom indicated bad vacuum tubes?

Any other way to check vacuum tube??
 

Blue Strat

Member
Messages
30,197
Brightness varies between different brands and types of tubes. Typically, if you see it lit up at all, it's lit up as much as it's going too.

However, lighting up doesn't mean that the tube is fully functional, or functional at all.

The only way to test unknown tubes is with a tester or by comparing their performance with known good tubes.

Is this a new piece of gear or is it used?
 

pdf64

Member
Messages
7,931
Sway the tubes over (bright for dim).
Does the dim / bright character follow the tubes or stay with the sockets?
 

donnyjaguar

Member
Messages
4,194
I think this is normal. I have some bright tubes and some so dim you wonder if they're on. I think its just however much of the filament is in view.

BTW, this is a good pre from what I recall.
 

J M Fahey

Member
Messages
2,940
Different filament brightness means they are built different.

Which means they are different types, maybe even different manufacturers.

Yet all have the same Prima Luna silkscreening.
 

Peteyvee

Premium Platinum Member
Messages
56,049
Are you sure it's not the active speakers you're using? Try swapping sides (L/R) with them and see if it follows the speaker.
 

Peteyvee

Premium Platinum Member
Messages
56,049
So you only have one speaker for a 2 channel stereo preamp? I'm afraid I don't understand.
 






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