Hi,
One thing to keep in mind is that the origin of some valves is not always easy to track down.
An inordinate amount of dirt cheap Eastern-European valves have been rebranded to whatever seemed the most profitable brand at the time.
Mullard, Philips, you name it.
Most of those small signal tubes from Eastern-Europe being cheap and often not very reliable never made it to the A suffix for reasons of tight economics or whatever.
I'm not saying the Mullard valves that showed to be problematic are in any way fake, Mullard and later Philips had plants all over the world and, besides that, some batches of British made Mullard could still have hit the market even though they were a bit "flaky" somehow....
As said before, merely technically speaking the flashing heaters should not be of any concern.
So unless the valve is of questionable quality/origin, no worries really.
Cheers,
One thing to keep in mind is that the origin of some valves is not always easy to track down.
An inordinate amount of dirt cheap Eastern-European valves have been rebranded to whatever seemed the most profitable brand at the time.
Mullard, Philips, you name it.
Most of those small signal tubes from Eastern-Europe being cheap and often not very reliable never made it to the A suffix for reasons of tight economics or whatever.
I'm not saying the Mullard valves that showed to be problematic are in any way fake, Mullard and later Philips had plants all over the world and, besides that, some batches of British made Mullard could still have hit the market even though they were a bit "flaky" somehow....
As said before, merely technically speaking the flashing heaters should not be of any concern.
So unless the valve is of questionable quality/origin, no worries really.
Cheers,