Modded Counterpoint SA3.1,tubes substituted for???

I have had this preamp for about 5 years now and I need to replace the tubes. A year or so ago I bought three 6DJ8s and installed them. I only got sound through the phono stage. Close inspection of the previous phono-stage tubes revealed no markings but I'm pretty convinced that the mods that were done to this unit caused it to use different model tubes in the phono-stage. Is there a common mod to replace those 6DJ8s with a superior tube? How do I find out what kind of tubes these are if all of the markings are rubbed off? This mod was not done by AltaVista and I have no way of reaching the guy who sold it to me. Would pics help identify the tubes?

ps. I ended up just reinstalling the older tubes but now I REALLY need to replace those so any help would be greatly appreciated.
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You better mail Mike to be sure.No one except him without looking at unit is likely to know except another tech.Hard to fix a bike or modded unit over the net or phone.He will get you started in right direction,Bob