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.
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