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The H output tubes in color sets (like 6JE6, 6JS6 etc.) are run at their absolute heat limit with no 'headroom' for overcurrent. That's why it's imperative to dip the current. Highest 'safe' current would be around 210 ma, with 200 preferable for good longevity. Much below 200 and you start getting width and regulation issues.
Tubes like 6KD6 etc. are beefier by design and can take more overcurrent, a requirement with the feedback-type HV regulation used in some Admirals.
B&W sets normally don't have these issues since the HO tubes run with adequate 'headroom'.
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