SECURITIES AND EXCHANGE COMMISSION
Washington, DC 20549
Under the Securities and Exchange Act of 1934
(Amendment No. 1 )
TENCOR INSTRUMENTS
(Name of Issuer)
Common
(Title of Class of Securities )
880323100
(CUSIP NUMBER)
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1) Name of Reporting
SS or IRS Identification Pioneering Management
Nos. of Above Persons Corporation
2) Check the Appropriate Box (a)
of A Member of Group
(See Instructions) (b) X
3) SEC Use Only
4) Citizenship of Place of
Organization
Number of (5) Sole Voting Power 2940000
Shares
Beneficially Owned (6) Shared Voting Power 0
by Each Reporting
Person With (7) Sole Dispositive 60000
Power
(8) Shared Dispositive 2880000
Power
9) Aggregate Amount Bene- 2940000
ficially Owned by Each
Reporting Person
10) Check if the aggregate
Amount in Row (9) Ex-
clude Certain Shares (See
Instructions)
11) Percent of Class Represented
By Amount in Row 9. 9.48%
12) Type of Reporting
Person (See Instructions) IA
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Item 1(a) Name of Issuer.
TENCOR INSTRUMENTS
Item 1(b) Address of User's Principal Executive Office's
Mr. Bruce R. Wright
Chief Financial Officer
TENCOR INSTRUMENTS
3333 Octavius Street
Santa Clara,CA 95054
Item 2(a) Name of Person Filing.
Pioneering Management Corporation
Item 2(b) Address of Principal Business Office:
60 State Street, Boston, MA 02109
Item 2(c) Citizenship:
State Of Delaware - Pioneering Management Corporation.
Item 2(d) Title of Class of Securities.
Common Stock
Item 2(e) CUSIP Number.
880323100
Item 3 The person filing this statement pursuant to Rule 13-1(b)
or 13d-2 is:
(a) Investment Adviser registered under Section
203 of the Investment Advisers Act of 1940.
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Item 4. Ownership
(a) Amount Beneficially Owned 2940000
(b) Percent of Class 9.48%
(c) Number of shares as to which such person has
(i) sole power to vote or to direct the vote 2940000
(ii) shared power to vote or to direct vote 0
(iii) sole power to dispose or to direct disposition of 60000
(iv) shared power to dispose or to direct disposition 2880000
Item 5. Ownership of Five Percent or Less of a Class.
Inapplicable.
Item 6. Ownership of More than Five Percent on Behalf of Another Person.
Inapplicable.
Item 7. Identification and Classification of the Subsidiary Which Acquired
the Security Being Reported On By the Parent Holding Company.
Inapplicable.
Item 8. Identification and Classification of Members of the Group.
Inapplicable.
Item 9. Notice of Dissolution of the Group.
Inapplicable.
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Item 10. Certification.
By signing below I certify that, to the best of my knowledge and
belief, the securities referred to above were acquired in the ordinary course of
business and were not acquired for the purpose of and do not have the effect of
changing or influencing the control of the issuer of such securities and were
not acquired in connection with or as a participant in any transactions having
such purposes or effect.
After reasonable inquiry and to the best of my knowledge and believe, I
certify that the information set forth in this statement is true, complete and
correct.
January 27, 1997
Date
/s/ William H. Keough
Signature
William H. Keough, Senior Vice President
Chief Financial Officer and Treasure
Type Name and Title
