Exhibit 10.13

Fleet Bank

August 30, 1996


Mr. Sebastian J. Sicari
Chief Financial Officer
Aseco Corporation
500 Donald Lynch Boulevard
Marlboro, MA 01752

Dear Sebastian:

Reference is hereby made to the Letter Agreement (the "Agreement") executed
by and between Aseco Corporation and Fleet Bank of Massachusetts, N.A. as of
November 27, 1992 and amended as of July 30, 1993, August 2, 1994 and
August 24, 1995.  We are pleased to inform you that we have approved an
extension of the Expiration Date from September 1, 1996 to September 1, 1997.
Nothing herein shall be deemed to constitute a waiver, release or amendment
of any other terms of the agreement.

The Borrower represents and warrants that the execution of this amendment has
been duly authorized by the Borrower by all necessary corporate and other 
action and that the execution will not conflict with, violate the provisions
of, or cause a default or constitute an event which, with the passage of time or
giving of notice or both, could cause a default on the part of the Borrower
under its charter documents or by-laws or under any contract, agreement, law,
rule, order, ordinance, franchise, instrument or other document, or result in
the imposition of any lien or encumbrance on any property or asset of the
Borrower.

The Borrower further represents that this agreement and the attached 
Promissory Note each represent legal, valid and binding obligations of the
Borrower, enforceable against the Borrower in accordance with their 
respective terms.  In addition, the statements, representations and warranties 
made in the Agreement continue to be correct as of the date hereof and the
Borrower is in compliance with all terms of the Agreement.  Except as 
expressly affected hereby, the Agreement remains in full force and effect as
heretofore.

Sebastian, we are pleased to extend the Agreement and look forward to 
continuing our relationship with Aseco Corporation.  Please sign below and
execute the attached note to evidence your acceptance of this amendment.

Sincerely,

Tom W. Davies
Vice President, High Technology Group


Agreed and Accepted:          Sebastian J.Sicari
8/30/96                     ----------------------
                            Vice President and CFO

Fleet Bank of Massachusetts, N.A., A Member of Fleet Financial Group
<PAGE>
Fleet Bank
Commercial Promissory Note

Boston, Massachusetts         August 30, 1996


FOR VALUE RECEIVED, I, the undersigned, promise to pay to the order of Fleet
National Bank, National Association (with any subsequent holder referred to
in this note as "you") at any of your offices, the sum of Five Million
and 00/100 -------DOLLARS ($5,000,000.00) with Interest in accordance with 
the provisions below which are marked.

INTEREST RATE
I will pay Interest on the unpaid principal balance of this Note as follows,
but in no event will Interest exceed the maximum rate permitted by law;

[x]   FLOATING RATE.  At the aggregate of the Bank's Prime Rate as the Bank
announces it from time to time, plus zero (0) percent per annum.  Changes
in the Bank's Prime Rate as the Bank announces it from time to time are to
take effect, for the purposes of the determination of Interest on this Note,
when made effective generally to loans by the Bank.

[ ]   FIXED RATE.  At the rate of ____ percent per annum.


[ ]   DISCOUNT. Interest to maturity has been deducted from the proceeds of
this Note, Interest at the rate of ____ percent   per annum shall be paid on
any amount not paid when due hereunder until that amount and any such 
Interest are so paid.

INTEREST PAYMENTS
I will pay interest at the above rate as follows:

[x]   PERIODICALLY.  Monthly/Quarterly/Monthly, in arrears, with the first
such payment due on the 30th day of September, 1996 and each subsequent
payment due on the corresponding day of each calendar month/calendar
quarter/ __________ thereafter.

[ ]   AT MATURITY.  At the maturity of this Note.


[ ]   INTEREST INCLUDED IN REPAYMENTS.  Interest is included in the 
payment(s) to be made pursuant to the Repayment Provisions below.

REPAYMENT PROVISIONS
In addition to any interest payments to be made as indicated above, I will
pay you the amount stated above as follows:

[ ]   ON DEMAND.  On demand by you.

[ ]   PAYMENTS TO BE MADE UNTIL DEMAND. On demand by you, with payments of
$________ each to be made monthly unless and until such demand is made.  The
first such payments shall be due on the______ day of________, 19__ (if you
have not made demand before then) and unless and until you make demand, each
subsequent payment shall be due on the corresponding day of each month 
thereafter.

[x]   TIME. _____ days after the date hereof on September 1, 1997.


     INSTALLMENTS.  In ________ consecutive monthly installments, of____ 
which each but the last shall be $_____ and the final of which shall be
equal to the then unpaid principal balance of this Note plus all accrued and 
unpaid interest thereon. The first      such monthly installment shall be due
on the ____ day of_________, 19__ and each subsequent installment shall be
due on the corresponding day of each month thereafter, with the balance of
all principal and interest due on ________, 19__.

<PAGE>
PREPAYMENT.  I will be entitled to prepay this note as follows:

LATE CHARGES.  If the entire amount of any required principal and/or Interest
is not paid in full within ten (10) days after the same is due, the Borrower
shall pay to the Bank a late fee equal to five percent (5%) of the required
payment provided that such late fee shall be reduced to three percent (3%) of
any required principal and Interest payment that is not paid within fifteen
(15) days of the date it is due if this Agreement is secured by a mortgage on
an owner-occupied residence, 1-4 units.

APPLICATION OF PAYMENTS.  Any payments you receive from me will be applied 
first to any accrued and unpaid interest and then to the unpaid principal
balance of this Note.  If any payment under this Note becomes due and payable
on the day upon which your office is legally closed to business, the due date
shall be extended to the next succeeding business day and interest shall be
payable during such extension at the rate stated above.

EACH BORROWER AND ENDORSER LIABLE.  If more than one borrower has signed 
below, each of us has made all of the promises contained in this Note, and we
are jointly and severally liable for all obligations on this Note.  If one or
more endorser has signed below, each endorser agrees to all terms of this 
Note, including without limitation the provisions relating to Security.

This Note is subject to the terms, provisions and conditions set forth on the
reverse side of this page.  Signed as an instrument under seal on the date
stated above.

BORROWER(S)

Aseco Corporation
------------------------------------
Name of Borrower


By:  Sebastian J. Sicari      Vice President and CFO
     -----------------------------------------------
     Name                     Title


Address:  500 Donald Lynch Boulevard
          ------------------------------------------

          Marlboro, Massachusetts 01752
          ------------------------------------------


ENDORSER(S):
----------------------------------------------------------------------
----------------------------------------------------------------------
<PAGE>
EVENTS OF DEFAULT. Upon the occurrence of any one or more of the following
Events of Default, the entire unpaid principal balance of this Note and all
unpaid accrued interest hereunder shall become immediately due and payable at
your option and without notice or demand.  In addition, at your option and
without notice or demand, the occurrence of any such Event of Default shall
also constitute a default under all agreements between you and me as well as
of all instruments and papers that I have given to you Events of Default are:
(a) my failure to pay when due (or upon demand, if payable on demand) any 
amount due on this Note or any other amount I owe you; (b) my failure
promptly, punctually, and faithfully to perform any other obligation or 
discharge any liability of mine to you; (c) your determination that any 
representation or warranty I made to you in any document, instrument,  
agreement or paper was not true or accurate when given; (d) the occurrence of 
any event of default under any agreement between you and me or under any 
instrument or paper I have given to you notwithstanding that you may not have
exercised your rights upon default under any such other agreement, instrument or
paper; (e) any act by, against, or relating to me or my 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 my property, the granting of any trust 
mortgage or execution of an assignment for the benefit of my creditors or the
occurrence of any other voluntary or involuntary liquidation or extension of
debt agreement for me; my written admission of my inability to pay my debts as
they mature; the filing of any complaint, application, or petition by or 
against me initiating any matter in which I am or may be granted any relief
from my debts pursuant to the Federal Bankruptcy Code or pursuant to any
other insolvency statute or procedure; my offering by or entering into any 
composition, extension, or any other arrangement seeking relief or extension
for my debts or any other judicial or non-judicial proceeding or agreement 
by, against, or including me which seeks or intends to accomplish a
reorganization or arrangement with creditors; (f) the imposition of any lien
upon my assets or the entry of any judgment against me, which lien is not 
discharged, or judgment appealed from or satisfied, within fifteen (15) days 
after its imposition or entry; (g) any material adverse change in my assets,
liabilities, property, business or condition, financial or otherwise; (h) the
occurrence of any event or circumstance with respect to me such that you deem 
yourself to be insecure; (i) my death, termination of existence, dissolution,
winding up, or liquidation; (j) the occurrence of any of the foregoing Events
of  Default with respect to any guarantor or endorser to you of my 
liabilities to you, as if such guarantor or endorser were a borrower who 
signed this Note.

     LOAN DOCUMENTS:SECURITY. The following loan documents and security
instruments are incorporated herein by reference with the same force and 
effect as if set forth herein in full:  Letter Agreement (the "Agreement")
executed by and between Aseco Corporation and Fleet National Bank (as 
successor to Fleet Bank of Massachusetts, N. A.) as of November 27, 1992 and
amended as of July 30, 1993, August 2, 1995 and August 30, 1996.

The execution, endorsement or guaranty of this Note constitutes a 
confirmation by each person that any security interest listed above which was
given to you before the date hereof shall continue in effect as security for 
this Note. In addition to the foregoing, any and all of the deposits or other 
sums at any time credited by or due from you to me or to any endorser or
guarantor of this Note, and any cash, securities, instruments, or other property
of mine or of such endorser or guarantor in your possession, whether for 
safekeeping, or otherwise, shall at all times constitute security for this 
Note and for any and all of my liabilities to you including, without
limitation, the liability evidenced hereby, and may be applied or set off by you
against such liabilities at any time whether or not such liabilities are then
due and whether or not other collateral is available to you.
<PAGE>
COSTS AND EXPENSES. I and each endorser and guarantor of this Note, will pay
all costs and expenses, including, without limitation, reasonable attorneys' 
fees and all expenses and disbursements of counsel, in connection with the 
protection or enforcement of any of your rights against me or any such endorser
and guarantor and against any collateral given to you to secure this Note or any
other of my liabilities or of such endorser and guarantor to you (whether or
not suit is instituted by or against you).

ASSIGNABILITY BY YOU. You may assign and transfer this Note to any person, firm 
or corporation and deliver to the assignee any collateral or security 
interest you hold in connection with this Note.  In the event of such 
assignment, you will have no further responsibility or liability with respect to
such collateral or security interest, and the terms of this Note and any 
related documents shall inure to the benefit of your assignee and its 
successors.  This Note shall be binding upon me and each endorser and
guarantor hereof and upon my and their respective heirs, successors, assigns, 
and representatives, and shall inure to the benefit of you and your successors 
and endorsees.

SEVERABILITY. If any provision of this Note is deemed by any court having 
jurisdiction thereof to be invalid or unenforceable, the other provisions of
this Note shall remain in full force and effect.  If any provision of this
Note is deemed by any such court to be unenforceable because such provision is 
too broad in scope, such provision shall be construed to be limited in scope to
the extent such court shall deem necessary to make it enforceable.  If any
provision is deemed inapplicable by any such court to any person or 
circumstances, it shall nevertheless be construed to apply to all other persons 
and circumstances.

WAIVER. No delay or omission by you in exercising or enforcing any of your
powers, rights, privileges, remedies, or discretions hereunder shall operate
as a waiver thereof on that occasion nor on any other occasion.  No waiver of
any default hereunder shall operate as a waiver of any other default hereunder,
nor as a continuing waiver.

ENDORSEMENT. Each endorser, jointly and severally if more than one, 
unconditionally guarantees prompt payment when due, by acceleration or 
otherwise, of this Note, regardless of its genuineness, validity, regularity
or enforceability and waives any right to require you to proceed against the
Borrower or any collateral which you might have been granted to secure and
endorser's liabilities under this Note.

PRESENTMENT, EXTENSION. I and each endorser and guarantor of this Note 
respectively waive presentment, demand, notices, and protest, and also waive
any delay on the part of the holder hereof.  Each assents to any extension or 
other indulgence (including, without limitation, the release of any other
party to this Note or the release or substitution of collateral) which you 
permit me or any such endorser or guarantor with respect to this Note or any 
collateral given to secure this Note and any other liability of mine or such 
endorser or guarantor to you.

MISCELLANEOUS. My liabilities and those of any endorser or guarantor of this 
Note are joint and several; provided, however, your release of me or any
endorser or guarantor shall not release any other person obligated on account
of this Note.  Each reference in this Note to me, any endorser, and any
guarantor, is to such person individually and also to all such persons
jointly.  No person obligated on account of this Note may seek contribution from
any other person also obligated unless and until all liabilities to you of 
the person from whom contribution is sought have been satisfied in full.

     I and each endorser and guarantor of this Note authorize you to complete
this Note if delivered in incomplete form, in any respect.
<PAGE>
     This Note is delivered to you at one of your offices in Massachusetts 
and shall be governed by the laws of the Commonwealth of Massachusetts.  I and 
each endorser and guarantor of this Note submit to the jurisdiction of the 
courts of the Commonwealth of Massachusetts for all purposes with respect to
this Note, any collateral given to secure their respective liabilities to you or
their respective liabilities to you or their respective relationships with you.