Replace Blank Spaces

i have a field with blank spaces.
i wanna replace the spaces with just one spaces. ihave 500 fields in 500 tables.

any input will be appreacited.

i have something like this but its not working.

declare @field varchar(50)
declare @minVoter int
declare @maxVoter int
declare @tableName varchar(20)

set @tablename = '00001'


-- select ad_str1 from [00170]

select @minVoter = min(id_voter),
@maxVoter = max(id_voter) from quotename(@tablename)


while (@minVoter <= @maxVoter)
begin
select @field = ad_str1
from quotename(@tablename)
where id_voter = @MinVoter


update [00170]
set ad_str1 = replace(@field, ' ', ' ')

select @minVoter = min(id_voter)
from quotename(@tablename)
where id_voter > @minvoter

end