Document:

<PAGE>
                                                                   EXHIBIT 10.25

                       FIFTH AMENDMENT TO PROMISSORY NOTES
                     AND EIGHTH AMENDMENT TO LOAN AGREEMENT

         THIS FIFTH AMENDMENT TO PROMISSORY NOTES AND EIGHTH AMENDMENT TO LOAN
AGREEMENT ("Amendment") is made as of January 23, 2003, by and between U.S. BANK
NATIONAL ASSOCIATION, a national banking association ("Bank") and QUALMARK
CORPORATION, a Colorado corporation ("Borrower").

                                    RECITALS:

         A. Bank made a revolving loan to Borrower, as evidenced by that certain
Promissory Note dated December 22, 1998 made by Borrower payable to Bank in the
original principal amount of $3,000,000 (the "Original Revolving Note"), as
amended and supplemented by that certain Modification/Extension Agreement
effective as of August 23, 1999 between Bank and Borrower (the "First
Amendment"), that certain Second Amendment to Promissory Notes and Fifth
Amendment to Loan Agreement dated as of February 1, 2001 (the "Second
Amendment"), that certain Third Amendment to Promissory Notes and Sixth
Amendment to Loan Agreement dated as of June 29, 2001 (the "Third Amendment"),
that certain Fourth Amendment to Promissory Notes and Seventh Amendment to Loan
Agreement dated as of January 31, 2002 (the "Fourth Amendment"), and that
certain Covenant Waiver and Amendment to Credit Agreement dated October 18, 2002
(the "10/02 Amendment"). Pursuant to the First Amendment, the principal amount
of the Revolving Note was reduced to $2,000,000. Pursuant to the Second
Amendment the principal amount of the Revolving Note was reduced to $1,000,000.
Pursuant to the 10/02 Amendment, the principal amount of the Revolving Note was
reduced to $750,000. The Original Revolving Note, as amended and supplemented by
the First Amendment, the Second Amendment, the Third Amendment, the Fourth
Amendment and the 10/02 Amendment is hereinafter called the "Revolving Note."

         B. Bank made a term loan to Borrower, as evidenced by that certain
Promissory Note dated December 22, 1998 made by Borrower payable to Bank in the
original principal amount of $2,000,000 (the "Original Term Note"), as amended
and supplemented by that certain Modification/Extension Agreement effective as
of August 23, 1999 between Bank and Borrower (the "Amendment to Term Note"), the
Second Amendment, the Third Amendment, the Fourth Amendment, that certain
Covenant Waiver and Amendment to Credit Agreement dated July 18, 2002 (the "7/02
Amendment") and the 10/02 Amendment. Pursuant to the Amendment to Term Note, the
principal amount of the Term Note was reduced to $1,262,017.47. Pursuant to the
Second Amendment, the principal amount of the Term Note was increased to
$2,000,000.00. The Original Term Note, as amended and supplemented by the
Amendment to Term Note, the Second Amendment, the Third Amendment, the Fourth
Amendment, the 7/02 Amendment and the 10/02 Amendment is hereinafter called the
"Term Note."

         C. The Revolving Note and the Term Note (collectively, the "Notes") are
subject to the provisions of that certain Revolving Credit and Term Loan
Agreement dated as of December 22,1998 between Borrower and Bank, as amended by
(i) Waiver and Amendment to Loan Agreement dated as of March 15, 1999, (ii)
Second Amendment to Loan Agreement dated as of

<PAGE>

August 23, 1999, (iii) Third Amendment to Loan Agreement dated as of March 31,
2000, (iv) Fourth Amendment to Loan Agreement dated as of August 2, 2000, (v)
the Second Amendment, (vi) the Third Amendment, (vii) the Fourth Amendment,
(viii) the 7/02 Amendment, and (ix) the 10/02 Amendment (as so amended, the
"Loan Agreement").

         D. All obligations of the Borrower to Bank are secured by a security
interest in (among other collateral) the Borrower's inventory, equipment, rights
to payment and general intangibles pursuant to Borrower's Security Agreement
between Borrower and Bank and the Addendum thereto, each dated December 22, 1998
(the "Security Agreement"), and that security interest has been properly
perfected. In addition, Borrower specifically assigned six (6) trademarks and
ten (10) patents pursuant to an Assignment of Security Interest in United States
Trademarks and Patents (the "Assignment" and collectively with the Security
Agreement, the "Security Documents") dated as of December 22, 1998 between
Borrower, as assignor, and Bank, as assignee. The Assignment was properly
recorded with the United States Patent and Trademark Office effective on January
14, 1999.

         E. Borrower and Bank desire to amend and supplement the Revolving Note,
the Term Note and the Loan Agreement, all as specifically hereinafter set forth.

                                   AGREEMENT:

         NOW, THEREFORE, in consideration of the foregoing recitals, the
agreements set forth herein and other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, the parties hereto
hereby agree as follows:

         1. Incorporation of Recitals. The foregoing recitals are hereby
incorporated herein and made a part hereof.

         2. Confirmation of Indebtedness. The outstanding principal balance
under the Revolving Note as of January 22, 2003 is $645,000.00. The outstanding
principal balance under the Term Note as of January 22, 2003 is $965,000.00.
Interest has and continues to accrue under the Notes in accordance with the
terms thereof.

         3. Amendments to Revolving Note. The terms of the Revolving Note are
changed as follows:

         A. The principal amount of the Revolving Note is reduced to
         $500,000.00.

         B. The maturity date of the Revolving Note is extended to March 15,
         2004. All principal remaining outstanding under the Revolving Note and
         all interest accrued thereon is payable in full on March 15, 2004.

         B. Borrower will pay all accrued interest under the Revolving Note on
         January 31, 2003. Commencing on February 1, 2003, Borrower will pay all
         accrued interest on the last day of each calendar month until maturity.

                                       2

<PAGE>

         4. Amendments to Term Note. The terms of the Term Note are changed as
follows:

         A. The principal amount of the Term Note is increased from the current
         outstanding principal balance of $965,000.00 (as of January 22, 2003)
         to $1,110,000.00.

         B. The maturity date of the Term Note is extended to March 15, 2004.
         All principal remaining outstanding under the Term Note and all
         interest accrued thereon is payable in full on March 15, 2004.

         C. Borrower will pay all accrued interest under the Term Note, plus
         $55,000 in principal, on January 31, 2003 and on or before the last day
         of each month thereafter through and including June 30, 2003.
         Commencing on July 1, 2003, Borrower agrees to pay all interest accrued
         under the Term Note, plus $65,000.00 in principal, on the last day of
         each month until maturity.

         5. Amendment to Loan Agreement. The Loan Agreement is amended as
follows:

         A. Section 1.01.1 of the Loan Agreement is amended by reducing the
         "Maximum Line" to $500,000.00.

         B. Section 1.01.2(a) of the Loan Agreement is amended by changing the
         "Termination Date" to March 15, 2004.

         C. Section 1.01.6 of the Loan Agreement is amended by changing the date
         "March 25, 2003" to "March 15, 2004."

         D. Section 1.02.4 of the Loan Agreement is amended by deleting the
         first sentence thereof and replacing it with the following:

         "Borrower agrees to repay the Term Loan made hereunder in monthly
         payments in the amount of $55,000, each due on the last day of each
         calendar month, commencing January 31, 2003 and continuing through and
         including June 30, 2003. Commencing on July 1, 2003, Borrower agrees to
         repay the Term Loan made hereunder in monthly payments in the amount of
         $65,000, and the final installment of all unpaid principal and accrued
         interest due and payable in full at the final maturity of the Term
         Loan, which will be March 15, 2004, subject to acceleration upon the
         occurrence of an Event of Default."

         E. Section 5.09 is deleted in its entirety and replaced with the
         following:

         "5.09 Financial Condition. Maintain the financial condition of
         Borrower, determined in accordance with GAAP, so that it meets the
         following requirements all measured on a calendar year basis beginning
         January 1, 2003 and ending on the dates set forth below:

                                       3

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         (a) Borrower's Tangible Net Worth will be not less than:

<Table>
<S>                   <C>
$1,700,000.00         As of March 31, 2003
$1,575,000.00         As of June 30, 2003
$1,575,000.00         As of September 30, 2003
$1,675,000.00         As of December 31, 2003
</Table>

         (b) Borrower's ratio of EBITDA to interest expense will be not less
             than:

<Table>
<S>                <C>
2.00:1             As of March 31, 2003
2.00:1             As of June 30, 2003
2.00:1             As of September 30, 2003
2.00:1             As of December 31, 2003
</Table>

         (c) Borrower's ratio of EBITDA to Debt Service will not be less than:

<Table>
<S>                <C>
..6                 As of March 3l, 2003
..5                 As of June 30, 2003
..5                 As of September 30, 2003
..6                 As of December 31, 2003
</Table>

         (d) Borrower's ratio of Debt to annualized EBITDA will not be more
             than:

<Table>
<Caption>
<S>               <C>
4:1               As of March 3l, 2003
4:1               As of June 30, 203
3:1               As of September 30, 2003
2:1               As of December 31, 2003
</Table>

         For purposes of this Section 5.09, "Tangible Net Worth" means
         stockholders' equity (including preferred stock) less intangible
         assets, and "Debt Service" means interest expense plus all mandatory
         principal payments on Debt."

         EBITDA shall be calculated on a year to date basis beginning January 1,
         2003 for each applicable period.

         6. Limited Waiver. Subject to the Borrower's agreement hereto, Bank
hereby waives any default that has occurred by reason of Borrower's failure to
comply with the covenants set forth in section 5.09 of the Loan Agreement as of
December 31, 2002.

         7. Conditions to Effectiveness of Amendment. This Amendment shall
become effective as of the date first above written when the Bank shall have
received and, as applicable, executed each of the following: (i) an original of
this Amendment, duly executed by the

                                        4

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Borrower; (ii) an extension fee equal to $16,100.00; (iii) attorneys' fees
incurred by Bank equal to $1,000.00; (iv) a Business Security Agreement, duly
executed by the Borrower; and (v) such additional information or documentation
as the Bank may require. If the Bank has not received all of the foregoing on or
before January 31, 2003, then the Bank's offer to make the agreements set forth
herein may be terminated, at the Bank's option, by giving notice to the
Borrower.

         8. General Release. Borrower, for and on behalf of itself and its legal
representatives, heirs, successors and assigns, does hereby waive, release,
relinquish and forever discharge Bank and its past and present directors,
officers, agents, employees, parents, subsidiaries, affiliates, insurers,
attorneys, representatives and assigns, and each and all thereof (collectively,
the "Released Parties"), of and from any and all manner of action or causes of
action, suits, claims, demands, judgments, damages, levies, and the execution of
whatsoever kind, nature and/or description arising on or before the date hereof,
including, without limitation, any claims, losses, costs or damages, including
compensatory and punitive damages, in each case whether known or unknown,
liquidated or unliquidated, fixed or contingent, direct or indirect, which
Borrower, or its legal representatives, heirs, successors or assigns, ever had
or now has or may claim to have against any of the Released Parties, with
respect to any matter whatsoever, including, without limitation, this Amendment
and any other instruments and agreements executed by Borrower in connection
herewith, arising on or before the date hereof.

         9. Effect of Amendment; Representations and Warranties; Nonwaiver. Bank
and Borrower agree that the Term Note, the Revolving Note and the Loan
Agreement, all as amended by this Amendment, and the Security Documents remain
in full force and effect. Borrower represents and warrants that its has the
power and legal right and authority to enter into this Amendment, and that
neither this Amendment, nor the agreements contained herein, contravene or
constitute a default under any agreement, instrument or indenture to which
Borrower is a party or signatory, or, to the best knowledge of Borrower, any
other agreement or requirement of law. Borrower represents and warrants that no
consent, approval or authorization of or registration or declaration with any
party, including but not limited to any governmental authority, is required in
connection with the execution and delivery by Borrower of this Amendment, or the
performance of its obligations herein described.

         10. Ratification of Notes, Loan Agreement and Security Documents. All
of the terms, conditions, provisions, agreements, requirements, promises,
obligations, duties, covenants and representations under the Revolving Note, the
Term Note, the Loan Agreement, all as amended and supplemented by this
Amendment, and the Security Documents are hereby ratified and affirmed in all
respects by Borrower. Borrower further represents and warrants that the Security
Documents continue to secure the obligations of Borrower under the Revolving
Note, the Term Note, the Loan Agreement, all as amended and supplemented by this
Amendment.

         11. Further Assurances. The Borrower shall promptly correct any defect
or error that may be discovered in any Security Document or in the execution,
acknowledgment or recordation thereof. Promptly upon request by the Bank, the
Borrower also shall do, execute, acknowledge, deliver, record, re-record,
file, re-file, register and re-register, any and all deeds, conveyances,
mortgages, deeds of trust, deeds, assignments, estoppel certificates, financing
statements

                                       5
<PAGE>
and continuations thereof, notices of assignment, transfers, certificates,
assurances and other instruments as Bank may reasonably require from time to
time in order: (a) to carry out more effectively the purposes of the Security
Documents; (b) to perfect and maintain the validity, effectiveness and priority
of any security interests intended to be created by the Security Documents; (c)
to grant the Bank, to secure the Notes, a perfected lien in any intellectual
property or other assets owned by the Borrower; and (d) to better assure,
convey, grant, assign, transfer, preserve, protect and confirm unto Bank the
rights granted now or hereafter intended to be granted to Bank under any
Security Document or under any other instrument executed in connection with any
Security Document or that the Borrower may be or become bound to convey,
mortgage or assign to Bank in order to carry out the intention or facilitate the
performance of the provisions of any Security Document. The Borrower shall
finish evidence satisfactory to Bank of every such recording, filing or
registration.

         12. Merger and Integration, Superseding Effect. This Amendment embodies
the entire agreement and understanding between the parties hereto with respect
to the subject matter hereof and supersedes and has merged into it all prior and
written agreements in the same subjects by and between the parties hereto with
the effect that this Amendment shall control.

         13. Counterparts. This Amendment may be executed in different
counterparts with the same effects as if the signatures thereon were in the same
instrument, and will be effective upon delivery of all such counterparts to
Bank.

         14. Governing Law. THE LAWS OF THE STATE OF COLORADO GOVERN THIS
AMENDMENT.

         15. Advice of Counsel. Borrower acknowledges and agrees that it has
received the advice of independent counsel selected by it, or the opportunity to
obtain such advice, before entering into this Amendment and any other
instruments and agreements executed by Borrower in connection herewith, and has
not relied upon Bank or any of its officers, directors, employees, agents or
attorneys concerning any aspect of the transactions contemplated by this
Amendment or any of the other said instruments and agreements.

                  (REMAINDER OF PAGE LEFT BLANK INTENTIONALLY)

                                       6

<PAGE>
         IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be
executed and delivered as of the date and year first above written.

                                      U.S. BANK NATIONAL ASSOCIATION

                                      By /s/ DANIEL J. FALSTAD
                                        ----------------------------------------
                                        Daniel J. Falstad, Vice President

                                      QUALMARK CORPORATION

                                      By /s/ ANTHONY SCALESE
                                        ----------------------------------------
                                        Anthony Scalese, Chief Financial Officer

STATE OF COLORADO          )
                           ) ss.
COUNTY OF ADAMS            )

         The foregoing instrument was acknowledged before me this 27 day of
January, 2003, by Anthony Scalese, the Chief Financial Officer of Qualmark
Corporation, a Colorado corporation, on behalf of the corporation.

                                       /s/ JEN GARDING
                                       -----------------------------------------
                                       Notary Public

                                                                          (SEAL)

                                       7<PAGE>
                                                                   EXHIBIT 10.26

                        (SILICON VALLEY BANK LETTERHEAD)

IRREVOCABLE STANDBY LETTER OF CREDIT NO. SVBSF001955

DATE: DECEMBER 19, 2002                                                  (STAMP)

BENEFICIARY:
CATELLUS DEVELOPMENT CORPORATION
A DELAWARE CORPORATION
12501 E. IMPERIAL HIGHWAY, SUITE 550
NORWALK, CA 90650
ATTENTION: ASSET MANAGEMENT

APPLICANT:
QUALMARK CORPORATION
1329 W. 121ST AVE.
DENVER, CO 80234

AMOUNT: US$90,000.00(U.S. DOLLARS NINETY THOUSAND EXACTLY)

EXPIRATION DATE: JULY 31, 2003

LOCATION: SANTA CLARA, CALIFORNIA

DEAR SIR/MADAM:

WE HEREBY ESTABLISH OUR IRREVOCABLE STANDBY LETTER OF CREDIT NO. SVBSF001955 IN
YOUR FAVOR AVAILABLE BY YOUR DRAFTS DRAWN ON US AT SIGHT IN THE FORM OF
"EXHIBIT B" ATTACHED AND ACCOMPANIED BY THE FOLLOWING DOCUMENTS:

1. THE ORIGINAL OF THIS LETTER OF CREDIT AND ALL AMENDMENT(S), IF ANY.

2. SIGHT DRAFTS DRAWN ON US.

3. A DATED CERTIFICATION FROM THE BENEFICIARY SIGNED BY AN AUTHORIZED OFFICER,
FOLLOWED BY ITS DESIGNATED TITLE, STATING THE FOLLOWING:

"QUALMARK CORPORATION, OR ITS SUCCESSORS OR ASSIGNS (COLLECTIVELY, TENANT) HAS
FAILED TO PAY RENT OR PERFORM ONE OR MORE OF ITS OBLIGATIONS UNDER THAT CERTAIN
(DESCRIBE NAME OF LEASE) (THE "LEASE") EXECUTED BY AND BETWEEN TENANT AND
CATELLUS DEVELOPMENT CORPORATION, A DELAWARE CORPORATION (CONFIRM THAT CDC IS
LANDLORD), OR TENANT FAILED TO REPLACE THIS LETTER OF CREDIT AS REQUIRED UNDER
THE TERMS OF THE LEASE, OR TENANT HAS FILED A VOLUNTARY PETITION UNDER THE
FEDERAL BANKRUPTCY CODE OR AN INVOLUNTARY PETITION HAS BEEN FILED AGAINST TENANT
UNDER THE FEDERAL BANKRUPTCY CODE. THE AMOUNT OF THE SIGHT DRAFT REPRESENTS
MONIES DUE AND OWING BY TENANT UNDER THE LEASE."

YOU SHALL NOT BE REQUIRED TO GIVE NOTICE OR MAKE PRIOR DEMAND OR PRESENTATION TO
TENANT WITH RESPECT TO THE PAYMENT OF ANY SUMS AS TO WHICH THE DRAW IS MADE
HEREUNDER.

PARTIAL DRAWS ARE ALLOWED. THIS LETTER OF CREDIT MUST ACCOMPANY ANY DRAWINGS
HEREUNDER FOR ENDORSEMENT OF THE DRAWING AMOUNT AND WILL BE RETURNED TO THE
BENEFICIARY UNLESS IT IS FULLY UTILIZED.

THIS LETTER OF CREDIT SHALL BE AUTOMATICALLY EXTENDED FOR AN ADDITIONAL PERIOD
OF ONE YEAR, WITHOUT AMENDMENT, FROM THE PRESENT OR EACH FUTURE EXPIRATION DATE
UNLESS AT LEAST NINETY (90) DAYS PRIOR TO THE THEN CURRENT EXPIRATION DATE WE
NOTIFY YOU BY REGISTERED MAIL/OVERNIGHT COURIER SERVICE AT THE ABOVE ADDRESS
THAT THIS LETTER OF CREDIT WILL NOT BE EXTENDED BEYOND THE CURRENT EXPIRATION
DATE. IN NO EVENT SHALL THIS LETTER OF CREDIT BE AUTOMATICALLY EXTENDED BEYOND
JULY 31, 2009.

                                                                        PAGE -1-
<PAGE>
                        (SILICON VALLEY BANK LETTERHEAD)

IRREVOCABLE STANDBY LETTER OF CREDIT NO. SVBSF001955

THIS LETTER OF CREDIT MAY ONLY BE TRANSFERRED IN ITS ENTIRETY BY THE ISSUING
BANK, ASSUMING SUCH TRANSFER TO SUCH TRANSFEREE WOULD BE IN COMPLIANCE WITH THEN
APPLICABLE LAW AND REGULATIONS, INCLUDING BUT NOT LIMITED TO THE REGULATIONS OF
THE U.S. DEPARTMENT OF TREASURY AND U.S. DEPARTMENT OF COMMERCE, UPON OUR
RECEIPT OF THE ATTACHED "EXHIBIT A" DULY COMPLETED AND EXECUTED BY THE
BENEFICIARY AND ACCOMPANIED BY THE ORIGINAL LETTER OF CREDIT AND ALL
AMENDMENT(S), IF ANY, TOGETHER WITH THE PAYMENT OF OUR TRANSFER FEE OF 1/4 OF 1%
OF THE TRANSFER AMOUNT (MINIMUM USD250.00).

DRAFT(S) AND DOCUMENTS MUST INDICATE THE NUMBER AND DATE OF THIS LETTER OF
CREDIT.

OUR OBLIGATION UNDER THIS LETTER OF CREDIT SHALL NOT BE AFFECTED BY AN
CIRCUMSTANCES, CLAIMS OR DEFENSE, REAL OR PERSONAL, OF ANY PARTY AS TO THE
ENFORCEABILITY OF THE LEASE BETWEEN YOU AND TENANT, IT BEING UNDERSTOOD THAT OUR
OBLIGATION SHALL BE THAT OF A PRIMARY OBLIGOR AND NOT THAT OF A SURETY,
GUARANTOR OR ACCOMMODATION MAKER. IF YOU DELIVER WRITTEN CERTIFICATION
REFERENCED ABOVE TO US. (I) WE SHALL HAVE NO OBLIGATION TO DETERMINE WHETHER ANY
OF THE STATEMENTS SET FORTH THEREIN ARE TRUE, (II) OUR OBLIGATIONS HEREUNDER
SHALL NOT BE EFFECTED IN ANY MANNER WHATSOEVER IF THE STATEMENTS MADE IN SUCH
CERTIFICATE ARE UNTRUE IN WHOLE OR IN PART, AND (III) OUR OBLIGATIONS HEREUNDER
SHALL NOT BE EFFECTED IN ANY MANNER WHATSOEVER IF TENANT DELIVERS INSTRUCTIONS
OR CORRESPONDENCE TO US WHICH EITHER (A) DENIES THE TRUTH OF THE STATEMENT SET
FORTH IN THE CERTIFICATE REFERRED TO ABOVE, OR (B) INSTRUCTS US NOT TO PAY
BENEFICIARY ON THIS LETTER OF CREDIT FOR ANY REASON WHATSOEVER.

DOCUMENTS MUST BE FORWARDED TO US BY OVERNIGHT DELIVERY SERVICE TO: SILICON
VALLEY BANK, 3003 TASMAN DRIVE, SANTA CLARA CAL 95054, ATTN: INTERNATIONAL
DIVISION.

WE HEREBY AGREE WITH THE DRAWERS, ENDORSERS AND BONAFIDE HOLDERS THAT THE DRAFTS
DRAWN UNDER AND IN ACCORDANCE WITH THE TERMS AND CONDITIONS OF THIS LETTER OF
CREDIT SHALL BE DULY HONORED UPON PRESENTATION TO THE DRAWER ON OR BEFORE 5:00
P.M. ON THE EXPIRATION DATE OF THIS CREDIT.

THIS LETTER OF CREDIT IS SUBJECT TO THE UNIFORM CUSTOMS AND PRACTICE FOR
DOCUMENTARY CREDITS (1993 REVISION), INTERNATIONAL CHAMBER OF COMMERCE,
PUBLICATION NO. 500.

SILICON VALLEY BANK,

/s/ ALICE E. DELUZ                          /s/ CESAR AGONCILLO
----------------------------------          ------------------------------------
AUTHORIZED SIGNATURE                        AUTHORIZED SIGNATURE
Alice E. Deluz                              CESAR AGONCILLO

                                                                        PAGE -2-

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