Quote:
Originally Posted by Yamamaya42
The 17BP4 & 17HP4 are identical mechanically and size wise, but differ as is the biasing, as in the 17BP4 is an older version, other than that, no dif, but that SHOULD have been stated on the box that it is a 17B not a 17H...
But it's pretty certain you have a 17BP4 there and it will be a pain to rig a circuit for focus for it. 
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Are you by chance confusing biasing with basing? Both share the same standard 12 pin basing with the exception a 17HP4 normally should have a focus pin in location 6.