alter table TBL add TBLJUNK3 char(20) not null default ''

That works fine. Now I want to remove it. I try:
  alter table TBL drop column TBLJUNK3
and it tells me
  The object 'DF__TBL__TBLJUNK3__084B3915' is dependent on column 'TBLJUNK3'.

I'm assuming that this funny thing is the default it created for this column for me. So I figure I should first try to clear the default before I drop the column, but I can't seem to drop or clear the default.

I tried:
  EXEC sp_unbindefault 'tbl.tbljunk3'
and it tells me to use ALTER TABLE DROP CONSTRAINT. But I can't get that to work.

I also tried
  alter table TBL alter column TBLJUNK3 drop default
and of course
  alter table TBL alter column TBLJUNK3 drop constraint
but all come back with syntax errors.

All I want to do is to delete a stupid column! What is the secret, and how come it's so hard? (Don't feel obliged to answer the last part of that.)

Thanks for your help. Tom