Last night I replaced the stock Electro-Harmonix 12AT7 driver tubes in my Jolida 502 with a matched pair of Telefunken's. One of the Tele's flashes a very bright white at power up. The tube then glows its normal red and seems fine in all respects. I have heard that the Mullards are notorious flashers, but I have never had a tube do this much less a good Telefunken. So my question: Should I be worried? Is this considered normal for some tubes? The flash appears to come from the base of the tube, but light can be tricky paricularly to the naked eye, and that observation cannot be considered etched in stone.
I'd welcome comments on this please.
I'd welcome comments on this please.