6EA8 , 6GH8 , 6U8 all compatible?
 

Going through my tubes i fing one that is nos , it says 6u8 / 6ea8 on the box and the tube , i look in the substitution book and see 6u8 will sub for 6ea8 but it notes parallel filamints , so my question is will a 6u8 work in place or 6ea8 ?

In most cases it will. I had trouble replacing a 6EA8 with one in a oscilloscope but that is the only trouble I have had.
That and 6GH8 tubes seem to have a death wish! I've replaced more of them than any other tube!

Yes i forgot to add that i didn't want to put 6gh8 in place of 6ea8 although more then one 6ea8 in the set has been replaced by 6gh8 , would prefer to put 6ea8 back in or 6u8 , as we all know 6gh8 new out of the box could have issues, it was just the parallel filaments warning that prompted me to post and get opinions.
mike

They're all pretty much compatible. I've subbed 6U8As for 6GH8s in color circuits (a pretty sensitive application) with no ill effects. Go for it! Hell I've seen triple marked 6U8A/6EA8/6GH8 tube boxes.

I think there's a 4 digit all numerical tube number that is also equivalent. 7199 maybe?

Different pinout...

Dynaco amplifier input/driver tube (7199). Expensive! Different pinout (as mentioned), very prone to heater to cathode shorts! Good ones getting scarce!

The better 6GH8 I find are the RCA and GE.
Check new ones before using! I've seen new ones bad. Especially the Asian ones near the end of production. The later RCA TV's devoured many of them.