I should probably ask this on the tube forum at the Asylum but I'll give it a shot here. I was digging through my stash and found two tubes that I bought a decade ago off of ebay. They were sold as Philips ECC82's. Both tubes are completely wiped except for some etched codes near the bottoms. One has the Herleen Delta followed by 2B3 and the other the Herleen Delta followed by 2B4. Also, looking at the bottoms, each has a single letter etched inside the glass. One with a capital H and another with a capital E.
I never used them because I was never 100% sure if they were 12AU7's or 12AX7's or one of the 9 pins with similiar internal construction. I havent been able to correlate the code with a tube type, I think its just manufacturing plant and date code but I dont know much about code. They have Halo getters and the half circle through one side of the plates and look like Amperex 12AU7 / ECC82's but I have 12AX7's that look the same. They are flashers, but I think a lot of the Amperex and other euro 9 pins were flashers. I tested them as 12AU7's and they test as such (relative to my known 12AU7's) but it's just an old heathkit emissions tester that I use to give me a very general idea of whether the tube is strong (atleast out of circuit) and mainly to test for shorts.
I didnt try testing a 12AX7 using 12AU7 settings (or vice versa) in the tester, I assume that I could try that without damaging the tester or the tube, but Im not positive. If I plugged them into one of my hi-fi amps that uses a 12AX7 preamp tube, I suppose I would easily notice the lower gain in the decreased output from the amp if they are indeed 12AU7's, right? I just dont want to roll one into Crack and do any damage if it's not a 12AU7/ECC82.
Any advice appreciated. Thanks.
