OVATION PRODUCTS CORPORATION

                                 Promissory Note

$60,000                       Boston, Massachusetts                 June 1, 2005


         FOR VALUE RECEIVED, the undersigned (the "Maker"), a Delaware
corporation having its offices at 6 Southgate Drive, Nashua, New Hampshire,
03062 promises to pay to the order SJE Rhombus, a Minnesota company with
principal offices at 22650 County Highway 6, Detroit Lakes, Minnesota, the
principal sum of SIXTY THOUSAND AND NO/100 DOLLARS ($60,000) or so much thereof
as is then outstanding under this Note, together with interest in arrears on the
unpaid principal balance from time to time outstanding at the rate hereinafter
set forth.

         Interest shall accrue, and be compounded monthly, on the amounts due
hereunder at the rate of Prime plus one percent (1%) per annum, or the maximum
rate under applicable law, if lower (the "Interest Rate"). Interest accrued
hereunder shall be payable monthly in arrears on the first day of each month.

         Upon the first to occur of (i) the Maturity Date (as hereinafter
defined), or (ii) an Event of Default (as hereinafter defined), the principal
and any unpaid interest shall thereafter accrue interest compounded monthly at
the Interest Rate plus seven percent (7%) per annum (the "Default Rate") until
all unpaid principal and interest (including default interest) is paid in full,
or at the highest rate that will not violate the applicable limits on interest
under the law. "Prime" shall mean the rate of interest reported as being the
"Prime Rate" in the Wall Street Journal (Eastern Edition) issued on the Friday
immediately preceding the date on which such rate is to be calculated hereunder.

         The entire outstanding principal balance hereof and all accrued and
unpaid interest thereon, and all other amounts due and payable under this Note
then unpaid shall be due and payable on June 1, 2006 (the "Maturity Date").

         The undersigned may prepay this Note from time to time in whole or in
part without premium or penalty in accordance with the terms set forth above.

         Any payments received by the Payee on account of this Note prior to
demand or acceleration shall be applied first to any costs, expenses, or charges
then owed the Payee by the undersigned, second to accrued and unpaid interest,
and third to the unpaid principal balance hereof. Any payments so received after
demand or acceleration shall be applied in such manner as the Payee may
determine. The undersigned hereby authorizes the Payee to charge any deposit
account which the undersigned may maintain with the Payee for any payment
required hereunder.

         The undersigned represents to the Payee that the proceeds of this Note
will not be used for personal, family or household purposes.

         The Payee, at its option, may declare the entire unpaid principal
balance of this Note to be immediately due and payable without demand, notice or
protest (which are hereby waived) upon the occurrence of any one or more of the
following events (herein, "Events of Default"):

      (a)   The failure by the undersigned to pay any amount due under this Note
            when due or within 10 days thereafter;

      (b)   The failure by the undersigned to promptly, punctually, and
            faithfully perform, discharge, or comply with any of the
            undersigned's liabilities, obligations, indebtedness or covenants to
            the Payee pursuant to this Note, any instrument or document executed
            and delivered pursuant thereto, or any agreement between the Payee
            and the undersigned, or any other instrument or paper given the
            Payee by the undersigned, whether such agreement, instrument, or
            paper now exists or hereafter arises (all of the foregoing, together
            with the indebtedness described in (a) are referred to herein as the
            "Liabilities");
<PAGE>

      (c)   (1) Any act by, against, or relating to the undersigned, or its
            property or assets, which act constitutes the application for,
            consent to, or sufferance of the appointment of a receiver, trustee,
            or other person, pursuant to court action or otherwise, over all or
            any part of the undersigned's property; (2) the granting of any
            trust mortgage or execution of an assignment for the benefit of the
            creditors of the undersigned, or the occurrence of any other
            voluntary or involuntary liquidation or extension of debt agreement
            for the undersigned; (3) the failure by the undersigned to generally
            pay the debts of the undersigned as they mature; (4) adjudication of
            bankruptcy or insolvency relative to the undersigned; (5) the entry
            of an order for relief or similar order with respect to the
            undersigned in any proceeding pursuant to the Bankruptcy Reform Act
            of 1978 (commonly referred to as the Bankruptcy Code) or any other
            federal bankruptcy law; (6) the filing of any complaint,
            application, or petition by or against the undersigned initiating
            any matter in which the undersigned is or may be granted any relief
            from the debts of the undersigned pursuant to the Bankruptcy Code or
            to any other insolvency statute or procedure; (7) the calling or
            sufferance of a meeting of creditors of the undersigned; (8) the
            meeting by the undersigned with a formal or informal creditors'
            committee; and/or (9) the offering by, or entering into by, the
            undersigned of any composition, extension or any other arrangement
            seeking relief or extension for the debts of the undersigned, or the
            initiation of any other judicial or non-judicial proceeding or
            agreement by, against, or including the undersigned, which seeks or
            intends to accomplish a reorganization or arrangement with
            creditors;

      (d)   The occurrence of any event such that any indebtedness of the
            undersigned in excess of Twenty Five Thousand Dollars ($25,000) due
            any lender or creditor other than the Payee could be accelerated,
            notwithstanding that such acceleration has not taken place;

      (e)   The occurrence of any event of default under any agreement between
            the Payee and the undersigned, or instrument or paper given the
            Payee by the undersigned, whether such agreement, instrument, or
            paper now exists or hereafter arises (notwithstanding that the Payee
            may not have exercised its rights upon default under any such other
            agreement, instrument, or paper);

      (f)   The entry of any judgment against the undersigned, which judgment is
            not satisfied or appealed from (with execution or similar process
            stayed) within fifteen (15) days of its entry;

      (g)   The termination of existence, dissolution, winding up or liquidation
            of the undersigned.

         In addition, at the Payee's option and without demand, notice or
protest, the occurrence of any such Event of Default shall also constitute a
default under all other agreements between the Payee and the undersigned, and
under all other instruments and papers given the Payee by the undersigned.

         No delay or omission by the Payee in exercising or enforcing any of the
Payee's powers, rights, privileges, remedies, or discretions hereunder shall
operate as a waiver thereof on that occasion nor on any other occasion. No
waiver hereunder shall operate as a waiver of any other action or right
hereunder, nor as a continuing waiver.
<PAGE>

         The undersigned agrees to and will pay on demand, all attorneys'
reasonable fees, out-of-pocket expenses incurred by the Payee's attorneys and
all costs incurred by the Payee, including, without limitation, costs and
expenses associated with travel on behalf of the Payee, which costs and expenses
are directly or indirectly related to the preservation, protection, collection
or enforcement of any of the Payee's rights against the undersigned or any
collateral given the Payee to secure this Note or any other liabilities of the
undersigned to the Payee (whether or not suit is instituted by or against the
Payee).

         The undersigned waives presentment, demand, notice, and protest, and
also waives any delay on the part of the holder hereof. The undersigned assents
to any extension or other indulgence (including, without limitation, the release
or substitution of collateral) permitted the undersigned by the Payee with
respect to this Note and/or any collateral given to secure this Note or any
extension or other indulgence, as described above, with respect to any other
liability or any collateral given to secure any other liability of the
undersigned to the Payee.

         This Note shall be binding upon the undersigned and upon its
successors, assigns, and representatives, and shall inure to the benefit of the
Payee and its successors, endorsees, and assigns.

         The undersigned hereby makes the following waiver, knowingly,
voluntarily, and intentionally, and understands that the Payee, in entering into
any loan arrangements or making any financial accommodations to the undersigned,
whether now or in the future, is relying on such waiver. THE UNDERSIGNED HEREBY
IRREVOCABLY WAIVES ANY PRESENT OR FUTURE RIGHT OF THE UNDERSIGNED TO A JURY IN
ANY TRIAL OF ANY CASE OR CONTROVERSY IN WHICH THE HOLDER IS OR BECOMES A PARTY
(WHETHER SUCH CASE OR CONTROVERSY IS INITIATED BY OR AGAINST THE HOLDER OR IN
WHICH THE HOLDER IS JOINED AS A PARTY LITIGANT), WHICH CASE OR CONTROVERSY
ARISES OUT OF OR IS IN RESPECT OF, ANY RELATIONSHIP BETWEEN THE UNDERSIGNED OR
ANY OTHER PERSON AND THE HOLDER.

         This Note is delivered to the Payee at its offices in Minnesota.


                                                 MAKER: ("the undersigned")
WITNESS as to Signature                          OVATION PRODUCTS CORPORATION
(Signed in my Presence):
                                                 By: /s/ William E. Lockwood
                                                 ----------------------------,
                                                 its President
/s/ Robert R. MacDonald
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