CounterPoint SA -5.1 Tubes...

good day,

i just hooked up a CounterPoint SA-5.1 preamp and the 5651 tube does not stay evenly lit, but rather 'pulses' every 3-4 seconds.

i have no experience with the pre-amp, so am wondering if this is normal, or should i replace the tube?

many thanks,
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I see the same kind of result in the Counterpoint SA-2 and Aria WV preamp that use the 5651. The 5651 resembles a vacuum tube and yet it really is not. It is simply a voltage reference filled with gas and acts more like a zener diode than a vacuum tube. So if this visually observed behavior of the 5651 is different than the other "tubes", don't worry about it.
thanks, Jafox... sounds like the 5651 tube is ok. thanks for checking your gear.