I have a 533 tester and a chart, but no settings for the 6GM8 / ECC86 tube. Settings I thought I found are a bit obscured and what I think they are, gives no reading at al with P4. Other roll charts, like for the 533A give settings and say only an English reading cam be made, but if I use those settings, the 2 tubes I have, one of which is unused, both come up as "bad" when P1 is pressed so I think those meter settings are wrong for this tester. Any help would be appreciated.