Some probate records for Berlin can be found in the online collection of the Family History Library. These records include records from the Superior Court of the Margraviate of Brandenburg covering the years 1796 to 1853. The collection does not yet have an index to the records, but the probates are arranged alphabetically by the surname of the deceased. These can be accessed at FamilySearch.org. Browse the images in the collection.
Testamentakten 1616-1849 [Indexes and calendars of wills] - microfilmed records in the Family History Library.
Wills probated in Berlin 1840-1844 - microfilmed records in the Family History Library.
Card file (index) to names contained in Kammergericht Testament (wills and probate records) filed at Berlin (High Court of Kurmark) on FHL fiche 6109218.