FT817 "power blobs" question

Having owned my FT817 (original version, not ND) for nearly 12 years I am almost too embarrassed to ask this question now.

http://upload.wikimedia.org/wikipedia/commons/5/55/Yaesu_FT-817_(1).jpg

When checking an old Bird RF power meter today I measured the power of my FT817 on and off a PSU at all power level settings. All these years I had assumed that "3 blobs" on the screen (when on a PSU) meant that I was putting out 5W. What I measured was closer to 2.5W. This did not change when the PSU was disconnected: still 2.5W. Then I pressed the button to "no blobs" and the power went up several dB, to I assume a nominal 5W. When on batteries it was "blinking 3 blobs". having re-read the FT817 (original) manual I was none the wiser: it does not mention a "no blobs" setting.

I think all these years when I had assumed my DX was being worked with 5W I was actually using just 2.5W. It looks like I should have gone to the "no blobs" setting with a PSU to get the full 5W.

So, can someone please clarify what power the FT817 should produce at all the different "blob" settings on batteries and on a 13.8V PSU?

UPDATE: I have the answer from Pete M3KXZ

Hi Roger.

On PSU:
- no blobs, output is 5W
- 3 blobs, 2.5W
- 2 blobs, 1W
- 1 blob, 0.5W

On internal batteries, the radio will default to "L///" and output 2.5W. If you
select high power, you will get 5W with "///" blinking. The other blobs are same
as for PSU.

I always run off external battery pack and the max power setting shows no blobs,
until the voltage starts to drop a bit when it automatically goes to "///"
blinking.

Well I'll be damned!  So for 12 years nearly I've been running 3dB less than I thought.