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                                  UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549




                              INITIAL SCHEDULE 13G




                    Under the Securities Exchange Act of 1934


                                   Vicor Corp
- --------------------------------------------------------------------------------
                                (Name of Issuer)

                                  Common Stock
- --------------------------------------------------------------------------------
                         (Title of Class of Securities)

                                    925815102
- --------------------------------------------------------------------------------
                                 (CUSIP Number)

                                December 31, 2000
- --------------------------------------------------------------------------------
             (Date of Event Which Requires Filing of the Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule
is filed:


                   [ X ]   Rule 13d-1(b)

                   [   ]   Rule 13d-1(c)

                   [   ]   Rule 13d-1(d)



The remainder of this cover page shall be filled out for a reporting person's
initial filing on this form with respect to the subject class of securities, and
for any subsequent amendment containing information which would alter the
disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the Securities Exchange Act of
1934 ("Act") or otherwise subject to the liabilities of that section of the Act
but shall be subject to all other provisions of the Act (however, see the
Notes).






                               PAGE 1 OF 10 PAGES


- ----------------------------------------- -------------------------------------- CUSIP No. 925815102 13G Page 2 of 10 Pages - ----------------------------------------- -------------------------------------- - ---------- ------------------------------------------------------------------------------------------------------------- 1 NAME OF REPORTING PERSON I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (entities only). John Hancock Financial Services, Inc. I.R.S. No. 04-3483032 - ---------- ------------------------------------------------------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP* (a) |_| (b) |_| N/A - ---------- ------------------------------------------------------------------------------------------------------------- 3 SEC USE ONLY - ---------- ------------------------------------------------------------------------------------------------------------- 4 CITIZENSHIP OR PLACE OF ORGANIZATION Delaware - ---------- ------------------------------------------------------------------------------------------------------------- 5 SOLE VOTING POWER Number of Shares -0- -------- ------------------------------------------------------------------------------------------- Beneficially 6 SHARED VOTING POWER Owned by Each -0- -------- ------------------------------------------------------------------------------------------- Reporting 7 SOLE DISPOSITIVE POWER Person With -0- -------- ------------------------------------------------------------------------------------------- 8 SHARED DISPOSITIVE POWER -0- - ---------- ------------------------------------------------------------------------------------------------------------- 9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON None, except through its indirect, wholly-owned subsidiary, John Hancock Advisers, Inc. - ---------- ------------------------------------------------------------------------------------------------------------- 10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES* N/A - ---------- ------------------------------------------------------------------------------------------------------------- 11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 See line 9, above. - ---------- ------------------------------------------------------------------------------------------------------------- 12 TYPE OF REPORTING PERSON* HC - ---------- ------------------------------------------------------------------------------------------------------------- *SEE INSTRUCTIONS BEFORE FILLING OUT! PAGE 2 OF 10 PAGES

- ----------------------------------------- -------------------------------------- CUSIP No. 925815102 13G Page 3 of 11 Pages - ----------------------------------------- -------------------------------------- - ---------- ------------------------------------------------------------------------------------------------------------- 1 NAME OF REPORTING PERSON I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (entities only). John Hancock Life Insurance Company I.R.S. No. 04-1414660 - ---------- ------------------------------------------------------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP* (a) |_| (b) |_| N/A - ---------- ------------------------------------------------------------------------------------------------------------- 3 SEC USE ONLY - ---------- ------------------------------------------------------------------------------------------------------------- 4 CITIZENSHIP OR PLACE OF ORGANIZATION Commonwealth of Massachusetts - ---------- ------------------------------------------------------------------------------------------------------------- 5 SOLE VOTING POWER Number of Shares -0- -------- ------------------------------------------------------------------------------------------- Beneficially 6 SHARED VOTING POWER Owned by Each -0- -------- ------------------------------------------------------------------------------------------- Reporting 7 SOLE DISPOSITIVE POWER Person With -0- -------- ------------------------------------------------------------------------------------------- 8 SHARED DISPOSITIVE POWER -0- - ---------- ------------------------------------------------------------------------------------------------------------- 9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON None, except through its indirect, wholly-owned subsidiary, John Hancock Advisers, Inc. - ---------- ------------------------------------------------------------------------------------------------------------- 10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES* N/A - ---------- ------------------------------------------------------------------------------------------------------------- 11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 See line 9, above. - ---------- ------------------------------------------------------------------------------------------------------------- 12 TYPE OF REPORTING PERSON* IC, IA, HC - ---------- ------------------------------------------------------------------------------------------------------------- *SEE INSTRUCTIONS BEFORE FILLING OUT! PAGE 3 OF 10 PAGES

- ----------------------------------------- -------------------------------------- CUSIP No. 925815102 13G Page 4 of 10 Pages - ----------------------------------------- -------------------------------------- - ---------- ------------------------------------------------------------------------------------------------------------- 1 NAME OF REPORTING PERSON I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (entities only). John Hancock Subsidiaries, Inc. I.R.S. No. 04-2687223 - ---------- ------------------------------------------------------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP* (a) |_| (b) |_| N/A - ---------- ------------------------------------------------------------------------------------------------------------- 3 SEC USE ONLY - ---------- ------------------------------------------------------------------------------------------------------------- 4 CITIZENSHIP OR PLACE OF ORGANIZATION Delaware - ---------- ------------------------------------------------------------------------------------------------------------- 5 SOLE VOTING POWER Number of Shares -0- -------- ------------------------------------------------------------------------------------------- Beneficially 6 SHARED VOTING POWER Owned by Each -0- -------- ------------------------------------------------------------------------------------------- Reporting 7 SOLE DISPOSITIVE POWER Person With -0- -------- ------------------------------------------------------------------------------------------- 8 SHARED DISPOSITIVE POWER -0- - ---------- ------------------------------------------------------------------------------------------------------------- 9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON None, except through its indirect, wholly-owned subsidiary, John Hancock Advisers, Inc. - ---------- ------------------------------------------------------------------------------------------------------------- 10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES* N/A - ---------- ------------------------------------------------------------------------------------------------------------- 11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 See line 9, above. - ---------- ------------------------------------------------------------------------------------------------------------- 12 TYPE OF REPORTING PERSON* HC - ---------- ------------------------------------------------------------------------------------------------------------- *SEE INSTRUCTIONS BEFORE FILLING OUT! PAGE 4 OF 10 PAGES

- ----------------------------------------- -------------------------------------- CUSIP No. 925815102 13G Page 5 of 10 Pages - ----------------------------------------- -------------------------------------- - ---------- ------------------------------------------------------------------------------------------------------------- 1 NAME OF REPORTING PERSON I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (entities only). The Berkeley Financial Group, Inc. I.R.S. No. 04-3145626 - ---------- ------------------------------------------------------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP* (a) |_| (b) |_| N/A - ---------- ------------------------------------------------------------------------------------------------------------- 3 SEC USE ONLY - ---------- ------------------------------------------------------------------------------------------------------------- 4 CITIZENSHIP OR PLACE OF ORGANIZATION Delaware - ---------- ------------------------------------------------------------------------------------------------------------- 5 SOLE VOTING POWER Number of Shares -0- -------- ------------------------------------------------------------------------------------------- Beneficially 6 SHARED VOTING POWER Owned by Each -0- -------- ------------------------------------------------------------------------------------------- Reporting 7 SOLE DISPOSITIVE POWER Person With -0- -------- ------------------------------------------------------------------------------------------- 8 SHARED DISPOSITIVE POWER -0- - ---------- ------------------------------------------------------------------------------------------------------------- 9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON None, except through its indirect, wholly-owned subsidiary, John Hancock Advisers, Inc. - ---------- ------------------------------------------------------------------------------------------------------------- 10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES* N/A - ---------- ------------------------------------------------------------------------------------------------------------- 11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 See line 9, above. - ---------- ------------------------------------------------------------------------------------------------------------- 12 TYPE OF REPORTING PERSON* HC - ---------- ------------------------------------------------------------------------------------------------------------- *SEE INSTRUCTIONS BEFORE FILLING OUT! PAGE 5 OF 10 PAGES

- ----------------------------------------- -------------------------------------- CUSIP No. 925815102 13G Page 6 of 10 Pages - ----------------------------------------- -------------------------------------- - ---------- ------------------------------------------------------------------------------------------------------------- 1 NAME OF REPORTING PERSON I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (entities only). John Hancock Advisers, Inc. I.R.S. No. 04-2441573 - ---------- ------------------------------------------------------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP* (a) |_| (b) |_| N/A - ---------- ------------------------------------------------------------------------------------------------------------- 3 SEC USE ONLY - ---------- ------------------------------------------------------------------------------------------------------------- 4 CITIZENSHIP OR PLACE OF ORGANIZATION Delaware - ---------- ------------------------------------------------------------------------------------------------------------- 5 SOLE VOTING POWER Number of Shares 1,827,450 -------- ------------------------------------------------------------------------------------------- Beneficially 6 SHARED VOTING POWER Owned by Each -0- -------- ------------------------------------------------------------------------------------------- Reporting 7 SOLE DISPOSITIVE POWER Person With 1,827,450 -------- ------------------------------------------------------------------------------------------- 8 SHARED DISPOSITIVE POWER -0- - ---------- ------------------------------------------------------------------------------------------------------------- 9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 1,827,450 - ---------- ------------------------------------------------------------------------------------------------------------- 10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES* N/A - ---------- ------------------------------------------------------------------------------------------------------------- 11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 6.0% - ---------- ------------------------------------------------------------------------------------------------------------- 12 TYPE OF REPORTING PERSON* IA - ---------- ------------------------------------------------------------------------------------------------------------- *SEE INSTRUCTIONS BEFORE FILLING OUT! PAGE 6 OF 10 PAGES

The original statement shall be signed by each person on whose behalf the statement is filed or his authorized representative. If the statement is signed on behalf of a person by his authorized representative other than an executive officer or general partner of the filing person, evidence of the representative's authority to sign on behalf of such person shall be filed with the statement, provided, however, that a power of attorney for this purpose which is already on file with the Commission may be incorporated by reference. The name and any title of each person who signs the statement shall be typed or printed beneath his signature. NOTE: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See ss.240.13d-7 for other parties for whom copies are to be sent. Attention: Intentional misstatements or omissions of fact constitute Federal criminal violations (See 18 U.S.C. 1001) Item 1(a) Name of Issuer: -------------- Vicor Corp Item 1(b) Address of Issuer's Principal Executive Offices: ----------------------------------------------- 25 Frontage Road Andover, MA 01810 Item 2(a) Name of Person Filing: --------------------- This filing is made on behalf of John Hancock Financial Services, Inc. ("JHF") JHF's direct, wholly-owned subsidiary, John Hancock Life Insurance Company ("JHLICO"), JHLICO's direct, wholly-owned subsidiary, John Hancock Subsidiaries, Inc. ("JHSI"), JHSI's direct, wholly-owned subsidiary, The Berkeley Financial Group, Inc. ("TBFG") and TBFG's wholly-owned subsidiary, John Hancock Advisers, Inc. ("JHA"). As a result of the demutualization of JHLICO, JHF became the parent holding company of JHLICO and may be deemed the beneficial owner of securities beneficially owned by JHLICO. Prior filings in respect of this holding were made by JHLICO (CIK No. 0000917406). Item 2(b) Address of the Principal Offices: -------------------------------- The principal business offices of JHF, JHLICO and JHSI are located at John Hancock Place, P.O. Box 111, Boston, MA 02117. The principal business offices of TBFG and JHA are located at 101 Huntington Avenue, Boston, Massachusetts 02199. Item 2(c) Citizenship: ----------- JHLICO was organized and exists under the laws of the Commonwealth of Massachusetts. JHF, JHSI, TBFG and JHA were organized and exist under the laws of the State of Delaware. Item 2(d) Title of Class of Securities: ---------------------------- Common Stock Item 2(e) CUSIP Number: ------------- 925815102 Item 3 If the Statement is being filed pursuant to Rule 13d-1(b), or ------------------------------------------------------------- 13d-2(b), check whether the person filing is a: ----------------------------------------------- JHF: (g) (X) Parent Holding Company, in accordance with ss.240.13d-1(b)(ii)(G). JHLICO: (c) (X) Insurance Company as defined in ss.3(a)(19) of the Act. (e) (X) Investment Adviser registered under ss.203 of the Investment Advisers Act of 1940. (g) (X) Parent Holding Company, in accordance with ss.240.13d-1(b)(ii)(G). JHSI: (g) (X) Parent Holding Company, in accordance with ss.240.13d-1(b)(ii)(G). PAGE 7 OF 10 PAGES

TBFG: (g) (X) Parent Holding Company, in accordance with ss.240.13d-1(b)(ii)(G). JHA: (e) (X) Investment Adviser registered under ss.203 of the Investment Advisers Act of 1940. Item 4 Ownership: --------- (a) Amount Beneficially Owned: -------------------------- JHA has direct beneficial ownership of 1,827,450 shares of Common Stock. Through their parent-subsidiary relationship to JHA, JHF, JHLICO, JHSI and TBFG have indirect, beneficial ownership of these same shares. (b) Percent of Class: 6.0% ---------------- (c) (i) sole power to vote or to direct the vote: JHA has sole power to vote or direct the vote of the 1,827,450 shares of Common Stock under the Advisory Agreements as follows: Date of Number Advisory Fund Name of Shares Agreement --------- --------- --------- John Hancock Insurance Company of VT Protected Cell No. V01 Hallmark (TOHI) 12,000 November 30, 2000 John Hancock Large Cap Value Fund 1,144,550 December 22, 1994 Raytheon 35,100 January 20, 2000 John Hancock Small Cap Value Fund 564,950 October 31, 1998 John Hancock Small Capitalization Value Fund -Y 30,650 April 3, 1995 V.A. Relative Value Fund 38,900 January 2, 1998 Private Accounts with Investment Management dates ranging from June 12, 2000 to November 29, 2000 1,300 (ii) shared power to vote or to direct the vote: -0- (iii) sole power to dispose or to direct the disposition of: JHA has sole power to dispose or to direct the disposition of the 1,827,450 shares of Common Stock under the Advisory Agreements noted in Item 4(c)(i) above. (iv) shared power to dispose or to direct the disposition of: -0- Item 5 Ownership of Five Percent or Less of a Class: -------------------------------------------- Not applicable Item 6 Ownership of More than Five Percent on Behalf of Another Person: --------------------------------------------------------------- See Item 4. Item 7 Identification and Classification of the Subsidiary which Acquired ------------------------------------------------------------------ the Security Being Reported on by the Parent Holding Company: ------------------------------------------------------------- See Items 3 and 4 above. Item 8 Identification and Classification of Members of the Group: --------------------------------------------------------- Not applicable. Item 9 Notice of Dissolution of a Group: -------------------------------- Not applicable. Item 10 Certification: ------------- By signing below the undersigned certifies that, to the best of its knowledge and belief, the securities referred to above were acquired in the ordinary course of business and were not acquired for the purpose of and do not have the effect of changing or influencing the control of the issuer of such securities and were not acquired in connection with or as a participant in any transaction having such purpose or effect. PAGE 8 OF 10 PAGES

SIGNATURE After reasonable inquiry and to the best of its knowledge and belief, each of the undersigned certifies that the information set forth in this statement is true, complete and correct. John Hancock Financial Services, Inc. By: /s/Barry J. Rubenstein ---------------------- Name: Barry J. Rubenstein Dated: February 9, 2001 Title: Vice President & Secretary John Hancock Life Insurance Company By: /s/Gregory P. Winn ------------------ Name: Gregory P. Winn Dated: February 9, 2001 Title: Vice President & Treasurer John Hancock Subsidiaries, Inc. By: /s/Gregory P. Winn ------------------ Name: Gregory P. Winn Dated: February 9, 2001 Title: Treasurer The Berkeley Financial Group, Inc. By: /s/Susan S. Newton ------------------ Name: Susan S. Newton Dated: February 9, 2001 Title: Senior Vice President John Hancock Advisers, Inc. By: /s/Susan S. Newton ------------------ Name: Susan S. Newton Dated: February 9, 2001 Title: Senior Vice President PAGE 9 OF 10 PAGES

EXHIBIT A JOINT FILING AGREEMENT ---------------------- John Hancock Financial Services, Inc., John Hancock Life Insurance Company, John Hancock Subsidiaries, Inc., The Berkeley Financial Group, Inc. and John Hancock Advisers, Inc. agree that the Initial Schedule 13G, to which this Agreement is attached, relating to the Common Stock of Vicor Corp is filed on behalf of each of them. John Hancock Financial Services, Inc. By: /s/Barry J. Rubenstein ---------------------- Name: Barry J. Rubenstein Dated: February 9, 2001 Title: Vice President & Secretary John Hancock Life Insurance Company By: /s/Gregory P. Winn ------------------ Name: Gregory P. Winn Dated: February 9, 2001 Title: Vice President & Treasurer John Hancock Subsidiaries, Inc. By: /s/Gregory P. Winn ------------------ Name: Gregory P. Winn Dated: February 9, 2001 Title: Treasurer The Berkeley Financial Group, Inc. By: /s/Susan S. Newton ------------------ Name: Susan S. Newton Dated: February 9, 2001 Title: Senior Vice President John Hancock Advisers, Inc. By: /s/Susan S. Newton ------------------ Name: Susan S. Newton Dated: February 9, 2001 Title: Senior Vice President PAGE 10 OF 10 PAGES