Bob,
That is normal, do NOT worry about it, some Euro tubes do that, especially Amperex,some Mullards, a few more. Just don't have any amplifiers on or the signal going to the amp, tubes need to dissipate their start up energy down for at least 30 seconds, that is why we put in a 30 second time delay output in all of our products. You would not want that start up energy to be passed thru your source,to the preamp and then to your speakers. Tubes need to settle down upon first start up. The flash which is definetly scary is the way it is and you should not be alarmed.
Now, if it was a power tube then there is a problem but that little 9 pin minature was built to do that. As Arnold would say "no problemo"
The golden rule for tube components when first turning on your system is source first, let it settle down for a minute or so, then tube preamp, let that settle down for at least a minute maybe two, then power amps.
When your done with your listening session, power down the amps first, then the preamp, then the source. The exact opposite of the turn on sequence.
Later,
Bill