<PAGE>

     THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE
SECURITIES ACT OF 1933 AND MAY NOT BE OFFERED OR SOLD ABSENT AN OPINION OF
COUNSEL SATISFACTORY TO THE ISSUER THEREOF THAT SUCH REGISTRATION HAS BEEN
EFFECTED OR AN EXEMPTION THEREFROM IS AVAILABLE.  TRANSFER MAY BE REFUSED IN THE
ABSENCE OF SUCH OPINION.

     This Replacement Promissory Note replaces the two Promissory Notes dated
April 5, 1999, payable on April 4, 2001 and April 4, 2002, respectively, issued
by Aerovox, Inc. to Bires Investments B.V.

AEROVOX INCORPORATED
Replacement Promissory Note



US $251,250                                              APRIL 4, 2001

     AEROVOX INCORPORATED, a Delaware corporation (hereinafter called the
"Company") for value received, hereby promises to pay to Bires Investments B.V.
at Amsterdam, Strawisnkylaan 1725, 1077 XX Amsterdam (hereinafter called
"Payee") the principal sum of US $251,250.00 (two hundred fifty-one thousand two
hundred fifty dollars and 00/100, currency of the United States of America),
together with all accrued but unpaid interest as follows: (i) US $63,152 (sixty-
three thousand one hundred fifty two) plus accrued but unpaid interest on April
4, 2002; (ii) US $63,152 (sixty-three thousand one hundred fifty two) plus
accrued but unpaid interest on July 4, 2002; (iii) US $63,152 (sixty-three
thousand one hundred fifty two) plus accrued but unpaid interest on October 4,
2002; and (iv) US $61,794 (sixty-one thousand seven hundred ninety-four) plus
accrued but unpaid interest on January 4, 2003. Interest shall accrue beginning
as of April 1, 2001 on the unpaid principal amount of this Note at a per annum
rate of interest equal to 8.22%. Principal and interest under this Note shall be
payable without setoff of any kind.

     For purposes of determining the person entitled to payment of the principal
of and interest on this Note, the Company is entitled to pay the person who is
the holder of this Note at the close of business on the third day (whether or
not a business day) next preceding the date for such payment.  All payments of
principal on this Note shall be payable at the address set forth above for such
holder or at such other place as such holder may from time to time in writing
appoint at least 15 days before the date such payment is due upon surrender of
this Note to the Company.

     This Note is transferable in whole, but not in part, without the prior
written consent of the Company, upon registration in the books and records of
the Company.  Unless a third party is appointed by the Company, the Company
shall act as Registrar and Transfer Agent with respect to this Note.  Upon
receipt of this Note duly endorsed for transfer, subject to compliance with the
Securities Act of 1933, as amended, the Company, at its cost, shall cause this
Note to be canceled and a new Note with the terms hereof to be issued to the
named transferee.
<PAGE>

     The Company may prepay all or any part of the principal amount of this Note
at any time on 30 days' prior written notice to the holder hereof.

     If any one or more of the following events (each of which is herein termed
an "event of default") shall happen, that is to say:

     (1)  Any default shall be made by the Company in any payment in respect of
principal or interest on this Note as the same shall become due, whether by
acceleration or otherwise, and such default shall continue for a period of three
business days;

     (2)  The Company shall be involved in financial difficulties as evidenced:

          (a)  by its admitting its inability to pay its debts generally as they
               become due or otherwise acknowledging its insolvency;

          (b)  by its filing a petition in bankruptcy or for reorganization or
               for the adoption of an arrangement under the United States
               Bankruptcy Act (or similar law of the United States or any other
               jurisdiction which relates to the liquidation or reorganization
               of companies or to the modification or alteration of the rights
               of creditors, each such law, as from time to time in effect,
               being sometimes referred to as a "bankruptcy act", each as now or
               in the future amended) or an answer or other pleading admitting
               or failing to deny the material allegations of such a petition or
               seeking, consenting to or acquiescing in the relief therein
               provided;

          (c)  by its making an assignment, or so-called trust mortgage or the
               like, for the benefit of its creditors or by its making a
               proposal to its creditors under any bankruptcy act;

          (d)  by its consent to the appointment of a receiver or a trustee (or
               other person performing a similar function) for all or a
               substantial part of its property;

          (e)  by its being adjudicated bankrupt;

          (f)  by the entry of a court order which shall not be vacated, set
               aside or stayed within 120 days form the date of entry, (i)
               appointing a receiver or a trustee for all or a substantial part
               of its property, or (ii) approving a petition filed or
               application made against it for, or effecting an arrangement in,
               bankruptcy or for a reorganization or other relief pursuant to
               any bankruptcy act or for any other judicial modification or
               alteration of the rights of creditors; or

          (g)  by the assumption of custody or sequestration by a court of
               competent jurisdiction of all or substantially all of its
               property, which custody or sequestration shall not be suspended
               or terminated within 120 days from its inception; or

                                      -2-
<PAGE>

     (3)  An "event of default" shall have occurred and be continuing under any
of the other Notes issued by the Company on the date hereof to Payee and any of
Renko Investments B.V., Kato Holding B.V., Hobir Holding B.V., Kasri Holding
B.V. and Tako Holding B.V;

then, Payee may declare the entire unpaid principal balance of the Note and all
accrued and unpaid interest immediately due and payable without notice.  Upon
the occurrence of an event of default, Payee shall be entitled to recover from
the Company, in addition to the unpaid principal balance and all accrued and
unpaid interest, all costs of collection incurred by Payee including, without
limitation, attorney's fees and court costs.

     An event of default shall not be deemed to be in existence for any purpose
of this Note if the registered holder of this Note shall have waived such event
in writing or stated in writing that the same has been cured to his reasonable
satisfaction, but no such waiver shall extend to or affect any subsequent event
of default or impair any of such holder's rights upon the occurrence thereof,
and no such waiver shall be granted unless and until notice of any such default
or notice of any event which, by the passage of time or otherwise, is expected
to result in an event of default shall have been received by Payee.

     Any notice required or permitted to be given hereunder shall be deemed
given if mailed, first class, postage prepaid, if to the holder, at Amsterdam,
Strawisnkylaan 1725, 1077 XX Amsterdam, or if to the Company, at 167 John
Vertente Blvd., New Bedford, Massachusetts 02745-1221, Attention:  Chief
Executive Officer, or in any case as either such person may designate to the
other in writing.

     The parties hereto, including the undersigned makers and all guarantors and
endorsers, hereby waive presentment, demand, notice, protest and all other
demands and notices in connection with the delivery, acceptance, performance and
enforcement of this Note, and assent to extensions of time of payment, or
forbearance or other indulgence without notice.  This Note shall be governed by
and construed in accordance with the laws of The Commonwealth of Massachusetts
without regard to conflict of law provisions.  Any dispute between Payer and
Payee with respect to this Note shall be resolved exclusively in accordance with
the arbitration procedures set forth in Clause 8.13 of the Purchase Agreement
dated as of April 5, 1999 by and between the Company and Payee.

     IN WITNESS WHEREOF, Aerovox Incorporated has caused this Note to be duly
executed under its corporate seal.

                                        AEROVOX INCORPORATED


                                        By _____________________________________
(CORPORATE SEAL)                           Name:
                                           Title:

                                      -3-