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                                                                   EXHIBIT 10.11

                      SENIOR SUBORDINATED CONVERTIBLE NOTE

$ 29,412,000.00                                               SEPTEMBER 30, 2003

FOR VALUE RECEIVED, the undersigned, Eagle Test Systems, Inc., an Illinois
corporation (the "BORROWER"), HEREBY PROMISES TO PAY to the order of TA
Subordinated Debt Fund, L.P. (the "NOTEHOLDER") the principal sum of $
29,412,000.00, together with interest on the unpaid principal amount from time
to time outstanding at the rate or rates and computed and payable at the times
as described in the Note Purchase Agreement (as hereinafter defined). Payments
of the principal hereof shall be made as provided in the Note Purchase
Agreement. Notwithstanding any other provision of this note, the entire balance
of principal and accrued and unpaid interest shall be paid in full on September
30, 2009.

      This note is one of the Convertible Notes referred to in the Note Purchase
Agreement dated as of September 30, 2003 (as the same may be amended, modified
or supplemented from time to time, the "NOTE PURCHASE AGREEMENT") among the
Borrower, the Noteholder and certain other Noteholders named therein.
Capitalized terms used herein and not otherwise defined shall have the meanings
set forth in the Note Purchase Agreement.

      The Noteholder may convert this note at any time pursuant to the terms of
the Note Purchase Agreement into (a) a Senior Subordinated Note due September
30, 2009 in the principal amount of $ 29,407,098.00 plus any interest owed in
arrears on this note on the Conversion Date, in the form attached hereto as
Exhibit A, and (b) a Common Stock Purchase Warrant of the Borrower for the
purchase of 205.900 shares of the Borrower's Common Stock (subject to adjustment
as provided for therein), exercisable at a price per share of $.01 (subject to
adjustment as provided for therein) in the form attached hereto as Exhibit B,
all as further described in the Note Purchase Agreement.

      Subject to, and at all times in accordance with, the provisions of the
Note Purchase Agreement (i) the Borrower shall have the right, at any time, to
voluntarily prepay all or any part of the outstanding principal amount of this
note, and (ii) the Noteholder shall have the right to require the Borrower to
repurchase this note upon the occurrence of a Mandatory Repurchase Event.

      In addition to the payment of interest as provided above, the Borrower
shall, on demand, pay interest on any overdue installments of principal and, to
the extent permitted by applicable law, on overdue installments of interest at
the rate set forth in, and in accordance with the provisions of, the Note
Purchase Agreement.

      The holder of this note is entitled to all the benefits and rights of a
Noteholder under the Note Purchase Agreement to which reference is hereby made
for a statement of the terms and conditions under which the entire unpaid
balance of this note, or any portion thereof, shall become immediately due and
payable. Notwithstanding anything in this note to the contrary, the

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terms and provisions of this note shall at all times be governed by and subject
to all of the terms and provisions of the Note Purchase Agreement. To the extent
that there is any conflict with, or inconsistency between, the terms and
provisions of this note and the terms and provisions of the Note Purchase
Agreement, the terms and provisions of the Note Purchase Agreement shall at all
times govern and control.

      The Borrower hereby waives presentment, demand, notice, protest and other
demands and notices in connection with the delivery, acceptance or enforcement
of this note.

      No delay or omission on the part of the holder of this note in exercising
any right hereunder shall operate as a waiver of such right or of any other
right under this note, and a waiver, delay or omission on any one occasion shall
not be construed as a bar to or waiver of any such right on any future occasion.

      The terms and provisions of this note are subject to the dispute
resolution provisions contained in Sections 9.11 and 9.12 of the Note Purchase
Agreement.

      This note shall be deemed to be under seal, and all rights and obligations
hereunder shall be governed by the laws of the State of New York (without giving
effect to any conflicts of law provisions contained therein).

                                        EAGLE TEST SYSTEMS, INC.

                                        By: Leonard Foxman
                                            ------------------------------
                                            Name:  Leonard Foxman
                                            Title: CEO<PAGE>

                                                                   EXHIBIT 10.12

                                                                  EXECUTION COPY

                            NON-COMPETITION AGREEMENT

      THIS NON-COMPETITION AGREEMENT is dated as of this 30th day of September,
2003, by and among Eagle Test Systems, Inc., an Illinois corporation (the
"Company"), Leonard A. Foxman (the "Stockholder") and the parties set forth on
the signature pages hereto as Investors (the "Investors").

                                   WITNESSETH

      WHEREAS, the Stockholder owns a direct equity interest in the Company (the
"Equity Interest");

      WHEREAS, the Company is in the business of designing, producing and
distributing automated test systems for use in the semiconductor industry (the
"Company Business");

      WHEREAS, the Company's business is conducted throughout the United States
and the rest of the world and the reputation and goodwill of the Company are an
integral part of its business success;

      WHEREAS pursuant to the terms of that certain Stock Purchase Agreement by
and among the Company, the Stockholders named therein and the Investors named
therein, dated as of the date hereof (the "Purchase Agreement"), (a) certain of
the Investors are purchasing shares of the Company's Series A Convertible
Preferred Stock, par value $.01 per share, for an aggregate purchase price of
$65,000,000 and (b) the Stockholder is receiving proceeds in the amount of
$48,339,484.10 pursuant to the redemption by the Company of a portion of the
Equity Interest;

      WHEREAS, pursuant to the terms of that certain Note Purchase Agreement by
and among the Company and certain of the Investors dated as of the date hereof
(the "Note Purchase Agreement"), such Investors are lending to the Company
$30,000,000 in return for convertible subordinated notes of the Company which
are convertible into subordinated notes of the Company and warrants to acquire
shares of Common Stock, par value $1.00 per share, of the Company;

      WHEREAS, as a material inducement to the Investors to enter into the
Purchase Agreement and Note Purchase Agreement and in consideration of the
covenants and agreements set forth therein, and in order to provide the
Investors with the full benefits of their investment, the Stockholder has agreed
to execute and deliver this Agreement; and

      WHEREAS, the execution and delivery by the Stockholder of this Agreement
is a condition precedent to the Investors' willingness to consummate the
transactions described in the Purchase Agreement and the Note Purchase
Agreement.

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      NOW, THEREFORE, in consideration of the mutual promises and covenants set
forth herein, the receipt and sufficiency of which are hereby acknowledged, the
parties hereto, intending to be legally bound, agree as follows:

      Section 1. Non-Competition; Non-Solicitation. In view of the fact that any
activity of the Stockholder in violation of the terms hereof would adversely
affect the Company and any subsidiaries and would deprive the Investors under
the Purchase Agreement and the Note Purchase Agreement of the benefits of their
bargains thereunder, and to preserve the goodwill associated with the Company's
business, the Stockholder hereby agrees to the following restrictions on his
activities:

            (a)   Non-Competition and Non-Solicitation. The Stockholder hereby
agrees that during the period commencing on the date hereof and ending on the
date which is the later of five (5) years after the date hereof or two (2) years
after termination of Stockholder's employment with the Company, if any, it will
not, without the express written consent of the Company, directly or indirectly,
anywhere in the United States or in any foreign country where the Company has
conducted business, is conducting business or is presently contemplating
conducting business, (a) engage in any activity which is or (b) participate or
invest in, provide or facilitate the provision of financing to, or assist
(whether as owner, part-owner, shareholder, member, partner, director, officer,
trustee, employee, agent or consultant, or in any other capacity) any business,
organization or person other than the Company (or any subsidiary of the
Company), including any such business, organization or person involving, or
which is, a family member of the Stockholder, whose business, activities,
products or services are competitive with any of the business, activities,
products or services conducted or offered by the Company or any of its
subsidiaries, which business, activities, products and services shall include in
any event and without limitation the Company Business. Without implied
limitation, the forgoing covenant shall be deemed to prohibit (a) hiring or
engaging or attempting to hire or engage for or on behalf of the Stockholder or
any such competitor any officer or employee of the Company or any of its
subsidiaries, or any former employee of the Company and any of its subsidiaries
who was employed during the six (6) month period immediately preceding the date
hereof, (b) encouraging for or on behalf of the Stockholder or any such
competitor any such officer or employee to terminate its relationship or
employment with the Company or any of its subsidiaries, (c) soliciting for or on
behalf of the Stockholder or any such competitor any client of the Company or
any of its subsidiaries and (d) diverting to any person any client or business
opportunity of the Company or any of any of its subsidiaries.

      Notwithstanding anything herein to the contrary, the Stockholder may make
passive investments in any publicly traded enterprise if such investment
constitutes less than one percent (2%) of the equity of such enterprise.

      Neither the Stockholder nor any business entity controlled by the
Stockholder is a party to any contract, commitment, arrangement or agreement
which could, following the date hereof, restrain or restrict the Company or any
subsidiary of the Company from carrying on its business or restrain or restrict
the Stockholder from performing the Stockholder's employment obligations, and,
as of the date of this Agreement, the Stockholder has no business interests
whatsoever in or relating to the industries in which the Company and its
subsidiaries currently engage other than the Stockholder's interest in the
Company and other than interests in public companies of less than one percent
(2%).

                                        2

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      For purposes of this Agreement, any reference to a (i) "subsidiary" or
"subsidiaries" of the Company shall be deemed to include any entities directly
or indirectly controlled by it through an ownership of more than fifty percent
(50%) of the voting interests and (ii) the term "person" shall mean an
individual, a corporation, an association, a partnership, a limited liability
company, an estate, a trust, and any other entity or organization.

      Section 2. Scope of Agreement. The parties acknowledge that the time,
scope, geographic area and other provisions of this Agreement have been
specifically negotiated by sophisticated commercial parties, and they agree that
(a) all such provisions are reasonable under the circumstances of the
transactions contemplated hereby, (b) are given as an integral and essential
part of the transactions contemplated hereby and (c) but for the covenants of
the Stockholder contained in this Agreement, the Company and the Investors would
not have entered into or consummated the transactions contemplated hereby. The
Stockholder has independently consulted with his counsel and has been advised in
all respects concerning the reasonableness and propriety of the covenants
contained herein, with specific regard to the business to be conducted by
Company and its subsidiaries, and represents that the Agreement is intended to
be, and shall be, fully enforceable and effective in accordance with its terms.

      Section 3. Confidentiality. The Stockholder agrees that all information,
whether or not in writing, concerning the Company Business or the Company's
technology, business relationships or financial affairs which the Company has
not released to the general public (collectively, "Proprietary Information") is
and will be the exclusive property of the Company. By way of illustration,
Proprietary Information may include information or material which has not been
made generally available to the public, such as: (a) corporate information,
including plans, strategies, methods, policies, resolutions, negotiations or
litigation; (b) marketing information, including strategies, methods, customer
identities or other information about customers, prospect identities or other
information about prospects, or market analyses or projections; (c) financial
information, including cost and performance data, debt arrangements, equity
structure, investors and holdings, purchasing and sales data and price lists;
and (d) operational and technological information, including plans,
specifications, manuals, forms, templates, software, designs, procedures,
formulas, discoveries, inventions, improvements, concepts and ideas; and (e)
personnel information, including personnel lists, reporting or organizational
structure, resumes, personnel data, compensation structure, performance
evaluations and termination arrangements or documents. Proprietary Information
also includes information received in confidence by the Company from its
customers or suppliers or other third parties. The Stockholder hereby agrees
that it will not, at any time, without the Company's prior written permission,
disclose any Proprietary Information to anyone outside of the Company, or use or
permit to be used any Proprietary Information for any purpose other than the
performance of my duties as an employee of the Company, if applicable. The
Stockholder hereby agrees to cooperate with the Company and use is best efforts
to prevent the unauthorized disclosure of all Proprietary Information.

      Section 4. Certain Remedies; Severability. It is specifically understood
and agreed that any breach of the provisions of this Agreement by the
Stockholder or any of his affiliates will result in irreparable injury to the
Company and its subsidiaries, that the remedy at law alone will be an inadequate
remedy for such breach and that, in addition to any other remedy it may have,
the Company and, upon authorization by the Board of Directors of the Company,
its subsidiaries shall be entitled to enforce the specific performance of this
Agreement by the Stockholder

                                        3

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through both temporary and permanent injunctive relief without the necessity of
proving actual damages, but without limitation of their right to damages and any
and all other remedies available to them, it being understood that injunctive
relief is in addition to, and not in lieu of, such other remedies. In the event
that any covenant contained in this Agreement shall be determined by any court
of competent jurisdiction to be unenforceable by reason of its extending for too
great a period of time or over too great a geographical area or by reason of its
being too extensive in any other respect, it shall be interpreted to extend only
over the maximum period of time for which it may be enforceable and/or over the
maximum geographical area as to which it may be enforceable and/or to the
maximum extent in all other respects as to which it may be enforceable, all as
determined by such court in such action. The existence of any claim or cause of
action which the Stockholder may have against the Company or any of its
subsidiaries shall not constitute a defense or bar to the enforcement of any of
the provisions of this Agreement.

      Section 5. Jurisdiction. The parties hereby irrevocably submit to the
non-exclusive jurisdiction of the courts of the State of Illinois to construe
and enforce the covenants contained in this Agreement. In the event that the
courts of any state shall hold such covenants unenforceable (in whole or in
part) by reason of the breadth of such scope or otherwise, it is the intention
of the parties hereto that such determination shall not bar or in any way affect
the right of the Company or, upon authorization by the Board of Directors of the
Company, any of its subsidiaries to the relief provided for herein in the courts
of any other state within the geographic scope of such covenants, as to breaches
of such covenants in such other respective states, the above covenants as they
relate to each state being, for this purpose, severable into diverse and
independent covenants.

      Section 6. Notices. Any notice or demand which is required or provided to
be given under this Agreement shall be deemed to have been sufficiently given
and received for all purposes when delivered by hand, telecopy, telex or other
method of facsimile, or five days after being sent by certified or registered
mail, postage and charges prepaid, return receipt requested, or two days after
being sent by overnight delivery providing receipt of delivery, to the following
addresses (or at such other address for any party as shall be specified by
notice given in accordance with the provisions hereof, provided that notices of
a change of address shall be effective only upon receipt thereof):

      If to the Company

      Eagle Test Systems, Inc.
      620 South Butterfield Road
      Mundelein, Illinois 60060
      Attention : Leonard A. Foxman

      If to the Investors:

      c/o TA Associates, Inc.
      125 High Street, Suite 2500
      Boston, Massachusetts 02110
      Attention: Michael C. Child and Jameson J. McJunkin
      Facsimile: (617) 574-6728

                                        4

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      If to the Stockholder:

      Leonard A. Foxman
      1929 Browning Ct.
      Highland Park, IL 60035

      Section 7. Miscellaneous. This Agreement shall be governed by and
construed under the laws of the State of Illinois and shall not be modified or
discharged in whole or in part except by an agreement in writing signed by the
Company, the Investors and the Stockholder. The failure of any of the parties to
require the performance of a term or obligation or to exercise any right under
this Agreement or the waiver of any breach hereunder shall not prevent
subsequent enforcement of such term or obligation or exercise of such right or
the enforcement at any time of any other right hereunder or be deemed a waiver
of any subsequent breach of the provision so breached, or of any other breach
hereunder. This Agreement shall inure to the benefit of, and be binding upon,
successors of the Company by way of merger, consolidation or transfer of
substantially all the assets of the Company, and may not be assigned by the
Stockholder. This Agreement supersedes all prior understandings and agreements
between the parties relating to the subject matter hereof.

                            [SIGNATURE PAGES FOLLOW]

                                        5

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      IN WITNESS WHEREOF, the parties have executed this Non-Competition
Agreement under seal as of the date first set forth above.

                                        COMPANY:

                                        EAGLE TEST SYSTEMS, INC.

                                        By: /s/ Leonard Foxman
                                            -----------------------------
                                            Name:  Leonard Foxman
                                            Title: President

                                        LEONARD FOXMAN:

                                        : /s/ Leonard Foxman
                                          ----------------------------

<PAGE>

INVESTORS:

                                        TA IX L.P.

                                        By: TA Associates IX LLC, its General
                                            Partner

                                        By: TA Associates, Inc., its Manager

                                        By: /s/ Michael C. Child
                                            ------------------------------------
                                            Name: Michael C. Child
                                            Title: Managing Director

                                        TA/ATLANTIC AND PACIFIC IV L.P.

                                        By: TA Associates AP IV L.P., its
                                            General Partner

                                        By: TA Associates, Inc., its
                                            General Partner

                                        By: /s/ Michael C. Child
                                            ------------------------------------
                                            Name: Michael C. Child
                                            Title: Managing Director

                                        TA STRATEGIC PARTNERS FUND A L.P.

                                        By: TA Associates SPF L.P., its
                                            General Partner

                                        By: TA Associates, Inc., its
                                            General Partner

                                        By: /s/ Michael C. Child
                                            ------------------------------------
                                            Name: Michael C. Child
                                            Title: Managing Director

<PAGE>

                                        TA STRATEGIC PARTNERS FUND B L.P.

                                        By: TA Associates SPF L.P., its
                                            General Partner

                                        By: TA Associates, Inc., its
                                            General Partner

                                        By: /s/ Michael C. Child
                                            ------------------------------------
                                            Name: Michael C. Child
                                            Title: Managing Director

                                        TA INVESTORS LLC

                                        By: TA Associates, Inc., its Manager

                                        By: /s/ Michael C. Child
                                            ------------------------------------
                                            Name: Michael C. Child
                                            Title: Managing Director

                                        TA SUBORDINATED DEBT FUND, L.P.

                                        By: TA Associates SDF LLC, its
                                            General Partner

                                        By: TA Associates, Inc., its Manager

                                        By: /s/ Michael C. Child
                                            ------------------------------------
                                            Name: Michael C. Child
                                            Title: Managing Director

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