Document:

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10(j)
                       FIRST AMENDMENT TO CREDIT AGREEMENT

                  THIS FIRST AMENDMENT TO CREDIT AGREEMENT, dated as of August
1, 2002 (this "Amendment"), is among KEITHLEY INSTRUMENTS, INC., an Ohio
corporation (the "Company"), Subsidiary Borrowers (referred to below and
collectively with the Company, the "Borrowers"), the Lender (as referred to
below) and BANK ONE, NA, a national banking association, having its principal
office in Columbus, Ohio, as Agent for the Lender (in such capacity the
"Agent").

                                    RECITALS

                  A. The Company, certain Subsidiary Borrowers party thereto,
the Lender party thereto and Agent are parties to a Credit Agreement, dated as
of March 30, 2001 (as now and hereafter amended, the "Credit Agreement"),
pursuant to which the Lender agreed, subject to the terms and conditions
thereof, to extend credit to the Borrowers.

                  B. The  Borrowers desire to amend the Credit Agreement and
the Agent and the Lender are willing to do so strictly in accordance with the
terms hereof.

                                      TERMS

                  In consideration of the premises and of the mutual agreements
herein contained, the parties agree as follows:

                                   ARTICLE 1.
                                   AMENDMENTS

                  Upon fulfillment of the conditions set forth in Article 3
hereof, the Credit Agreement shall be amended as follows:

         1.1 Article I shall be amended by adding the following definitions in
appropriate alphabetical order:

                  "Consolidated Current Assets" means, as of any date, all
         assets which, in accordance with Agreement Accounting Principles,
         should be classified as current assets on the consolidated balance
         sheet of the Company, provided that, prepaid assets shall be excluded,
         all calculated for the Company and its Subsidiaries on a consolidated
         basis.

                  "Consolidated Current Liabilities" means, as of any date, all
         liabilities which, in accordance with Agreement Accounting Principles,
         should be classified as current liabilities on the consolidated balance
         sheet of the Company, provided that, the Aggregate Outstanding Credit
         Exposure shall be included as "Consolidated Current Liabilities"
         hereunder, all calculated for the Company and its Subsidiaries on a
         consolidated basis.

                  "EBIDA Plus Non-Recurring Expense" means Consolidated Net
         Income plus, to the extent deducted from revenues in determining
         Consolidated Net Income, (i) Consolidated Interest Expense (without any
         netting against any interest income), (ii) depreciation, (iii)

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         amortization and (iv) non-recurring expenses prepared in accordance
         with Agreement Accounting Principles, all calculated for the Company
         and its Subsidiaries on a consolidated basis.

                  "Working Capital" means as of any date, the amount, if any, by
         which Consolidated Current Assets exceeds Consolidated Current
         Liabilities.

         1.2 Section 6.10 shall be amended by deleting the reference in clause
(b) therein to "25% of the Consolidated Net Income in any fiscal year" and
inserting "$3,000,000 in any fiscal year" in place thereof.

         1.3 Section 6.14 shall be amended by deleting the reference in clause
(iv)(f) therein to "50%" and inserting "10%" in place thereof.

         1.4 Section 6.16 shall be amended and restated in its entirety to read
as follows:

                  6.16.  FINANCIAL COVENANTS

                           6.16.1. FIXED CHARGE COVERAGE RATIO. The Company will
         not permit the Fixed Charge Coverage Ratio, determined as of the end of
         each of its fiscal quarters for the four most-recently ended fiscal
         quarters, to be less than 3.0 to 1.0, commencing with the fiscal
         quarter ending June 30, 2003. The Fixed Charge Coverage Ratio is
         suspended for the fiscal quarters ending June 30, 2002 through and
         including March 31, 2003.

                           6.16.2. LEVERAGE RATIO. The Company will not permit
         the Leverage Ratio, determined as of the end of each of its fiscal
         quarters, to be greater than 1.0 to 1.0, commencing with the fiscal
         quarter ending June 30, 2003. The Leverage Ratio is suspended for the
         fiscal quarters ending June 30, 2002 through and including March 31,
         2003.

                           6.16.3.  WORKING CAPITAL.  The Company will not
         permit Working Capital to be less than $40,000,000 at any time,
         determined as of the end of each fiscal quarter commencing June 30,
         2002 through and including March 31, 2003.

                           6.16.4. EBIDA PLUS NON-RECURRING EXPENSE. The Company
         will not permit the EBIDA plus Non-Recurring Expense, determined as of
         the end of each of its fiscal quarters for such fiscal quarter, to be
         less than: (i) as of June 30, 2002, ($500,000); (ii) as of September
         30, 2002, $0, (iii) as of December 31, 2002, $500,000, and (iv) as of
         March 31, 2003, $1,000,000.

                  1.5 Schedule 2 to the Credit Agreement shall be amended to add
         the Subsidiary referenced below:

           Keithley Instruments KK.     Organized under the laws of Japan.
                         100% Wholly-Owned Subsidiary.

                                      -2-
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                                   ARTICLE 2.
                                 REPRESENTATIONS

                  Each Borrower represents and warrants to the Agent and the
Lender that:

         2.1 The execution, delivery and performance of this Amendment is within
its powers, has been duly authorized and is not in contravention with any law,
of the terms of its Articles of Incorporation or By-laws, or any undertaking to
which it is a party or by which it is bound.

         2.2 This Amendment is the legal, valid and binding obligation of the
Borrower enforceable against it in accordance with the terms hereof.

         2.3 After giving effect to the amendments herein contained, the
representations and warranties contained in Article V of the Credit Agreement
are true on and as of June 30, 2002 with the same force and effect as if made on
and as of June 30, 2002.

         2.4 No Default or Unmatured Default exists or has occurred and is
continuing on the date hereof.

                                   ARTICLE 3.
                           CONDITIONS OF EFFECTIVENESS

                  This Amendment shall not become effective until each of the
following has been satisfied:

         3.1 This Amendment shall be signed by each Borrower, the Agent and the
Lender.

         3.2 The Company shall have paid an amendment fee in the amount of
$7,500.

                                   ARTICLE 4.
                                 MISCELLANEOUS.

         4.1 References in the Credit Agreement or in any note, certificate,
instrument or other document to the "Credit Agreement" shall be deemed to be
references to the Credit Agreement as amended hereby and as further amended from
time to time.

         4.2 The Company agrees to pay and to save the Agent harmless for the
payment of all costs and expenses arising in connection with this Amendment,
including the reasonable fees of counsel to the Agent in connection with
preparing this Amendment and the related documents.

         4.3 Each Borrower acknowledges and agrees that the Agent and the Lender
have fully performed all of their obligations under all documents executed in
connection with the Credit Agreement and all actions taken by the Agent and the
Lender are reasonable and appropriate under the circumstances and within their
rights under the Credit Agreement and all other documents executed in connection
therewith and otherwise available. Each Borrower represents and warrants that it
is not aware of any claims or causes of action against the Agent or any Lender,
any participant lender or any of their successors or assigns.

                                      -3-
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         4.4 Except as expressly amended hereby, each Borrower agrees that the
Credit Agreement and all other Loan Documents are ratified and confirmed and
shall remain in full force and effect and that it has no set off, counterclaim
or defense with respect to any of the foregoing. Terms used but not defined
herein shall have the respective meanings ascribed thereto in the Credit
Agreement.

         4.5 This Amendment may be signed upon any number of counterparts with
the same effect as if the signatures thereto and hereto were upon the same
instrument.

                  IN WITNESS WHEREOF, the parties signing this Amendment have
caused this Amendment to be executed and delivered as of August 1, 2002.

                           KEITHLEY INSTRUMENTS, INC.

                           By: /s/ Mark J. Plush
                               -------------------------------------------------

                               Its: Vice President and Chief Financial Officer
                                    --------------------------------------------

                           KEITHLEY INSTRUMENTS GMBH

                           By: /s/ Mark J. Plush
                               -------------------------------------------------

                               Its: Managing Director
                                    --------------------------------------------

                           BANK ONE, NA, as Agent, LC Issuer and Lender

                           By: /s/ James M. Malz
                               -------------------------------------------------

                               Its: First Vice President, Division Manager
                                    --------------------------------------------

                                      -4-<PAGE>
                                                                     Exhibit 4.2

                              ASSUMPTION AGREEMENT

To JPMorgan Chase Bank,                                            June 11, 2002
 as Administrative Agent party to the
 Credit Agreement referred to below

Ladies and Gentlemen:

        Reference is made to the Credit Agreement (the "CREDIT AGREEMENT") dated
as of April 12, 2001 between National City Corporation (the "BORROWER"), the
lenders party thereto and JPMorgan Chase Bank (formerly known as The Chase
Manhattan Bank), as Administrative Agent. Terms defined in the Credit Agreement
are used herein as defined therein.

        The Borrower and Morgan Stanley Bank (the "ASSUMING LENDER") each hereby
agree as follows:

        1. The Assuming Lender proposes to become an Assuming Lender pursuant to
   Section 2.07(e) of the Credit Agreement with a Commitment in the amount of
   $25,000,000 and, in that connection, hereby agrees with the Administrative
   Agent and the Borrower that it shall become a Lender for all purposes of
   the Credit Agreement on the applicable Commitment Increase Date.

        2. The Assuming Lender (a) confirms that it has received a copy of the
   Credit Agreement, together with copies of the financial statements referred
   to in Section 3.01 thereof and such other documents and information as it
   has deemed appropriate to make its own credit analysis and decision to enter
   into this Assumption Agreement; (b) agrees that it will, independently and
   without reliance upon the Administrative Agent or any other Lender and based
   on such documents and information as it shall deem appropriate at the time,
   continue to  make its own credit decisions in taking or not taking action
   under the Credit Agreement; (c) appoints and authorizes the Administrative
   Agent to take such action as agent on its behalf and to exercise such powers
   and discretion under the Credit Agreement as are delegated to the
   Administrative Agent by the terms thereof, together with such powers and
   discretion as are reasonably incidental thereto; and (d) agrees that it will
   perform in accordance with their terms all of the obligations that by the
   terms of the Credit Agreement are required to be performed by it as a
   Lender, including, without limitation the obligations of each Lender with
   respect to confidentiality set forth in Section 9.12(b) thereof.

        3.  Following the execution hereof, this Assumption Agreement will be
   delivered to the Administrative Agent for acceptance and recording by
   the
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                                      -2-

Administrative Agent. The effective date for this Assumption Agreement (the
"EFFECTIVE DATE") shall be the applicable Commitment Increase Date.

        4. Upon satisfaction of the applicable conditions set forth in Section
2.07(e) of the Credit Agreement and upon such acceptance and recording by the
Administrative Agent, as of the Effective Date, the Assuming Lender shall be a
party to the Credit Agreement and have all of the rights and obligations of a
Lender thereunder.

        5. This Assumption Agreement shall be governed by and construed in
accordance with, the law of the State of New York.

        6. This Assumption Agreement may be executed in any number of
counterparts and by different parties hereto in separate counterparts, each of
which when so executed shall be deemed to be an original and all of which taken
together shall constitute one and the same agreement. Delivery of an executed
counterpart of this Assumption Agreement by facsimile shall be effective as
delivery of a manually executed counterpart of this Assumption Agreement.

                              ASSUMPTION AGREEMENT

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                                      -3-

        IN WITNESS WHEREOF, the Borrower and the Assuming Lender have caused
this letter to be duly executed and delivered as of the date first above
written.

                                        Very truly yours,

                                        NATIONAL CITY CORPORATION

                                        By /s/ Thomas A. Richlovsky
                                          ----------------------------
                                          Name: Thomas A. Richlovsky
                                          Title: Senior Vice President
                                                 & Treasurer

                                        MORGAN STANLEY BANK

                                        By /s/ Jaap L. Tonckens
                                          ----------------------------
                                          Name: Jaap L. Tonckens
                                          Title: Vice President

Accepted this 11th day of June, 2002:

JPMORGAN CHASE BANK,
as Administrative Agent

By /s/ Roger A. Parker
  ------------------------------
  Name: Roger A. Parker
  Title: Vice President

                              ASSUMPTION AGREEMENT

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