Missing Terminals on an ST 10

[aerobat]

I just opened up the doghouse on my new ST-10 to wire it up.  The manual indicates that terminals U1 is to be connected to U6 and U2 to U5.  This all well and good except that the posts for U5 and U6 are missing!     It looks like the head could be wired for 50 Hz operation (U1-U4 and U2-U3) but not 60 Hz.  Has anyone else run into this problem?   
Thanks,
Doug

[aerobat]

I emailed the vendor from whom I purchased the head.  He indicated that the head should be wired using the same configuration as is used for 50 Hz operation.  (Makes sense since rotational speed determines output frequency).  I'm still a little puzzled as to why the manual indicates that there are 2 sets of posts and different wiring configurations.  Ah-well as long as it works-

Doug

[Doug]

Some machines have wires deleted, it just makes the connections easier. At 1800 rpm a ST head is spinning 20% faster and the output voltage will be about 20% higher as well. Do you have resistor or reostat in series with the field?

There is a down side to this, reducing the field current instead of making a tap changes reduces the flux density in the core, but on the upside it makes for a slightly cooler running machine and a little more quiet.

I think its more likely the Head you have was specificaly wound for 60 hz and not the other way around as the vender said. I'd email him again and ask if he has made a mistake