SCHEDULE 14A INFORMATION
 
                  Proxy Statement Pursuant to Section 14(a) of
            the Securities Exchange Act of 1934 (Amendment No.    )
 
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    / /  Soliciting Material Pursuant to Section240.14a-11(c) or
         Section240.14a-12
 
                                                HEI, INC.
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                (Name of Registrant as Specified In Its Charter)
 
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    (Name of Person(s) Filing Proxy Statement, if other than the Registrant)
 
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                                                                       Exhibit 8
 
                                                         Box 5000
                                                         1495 Steiger Lake Lane
                                                         Victoria, MN 55386
                                                         (612) 443-2500
                                                         Fax (612) 443-2668
 
                                                                    [LOGO]
 
                                 July 17, 1998
 
Dear Fellow Shareholder:
 
    There he goes again. Now Anthony J. Fant has raised the purchase price in
his partial tender offer FOR ONLY 11.5% OF HEI'S SHARES from $8 to $9 per share.
We believe this is simply another Fant tactic that draws attention away from the
real issues. Your Board unanimously recommends that you not tender your shares
to Fant. The enclosed amendment to Schedule 14D-9 sets forth our reasons for
that recommendation.
 
    In short, the Board believes that you should focus on the following:
 
    - Fant's amended offer is still for only 11.5% of HEI's shares (not for all
      the shares that you might want to sell). What does that mean to you? Based
      on Fant's figures, if you tender 100 shares, 68 of those shares would be
      sent back to you without any payment (and even more shares would be
      returned if more shares are tendered by other shareholders). THE FUTURE
      VALUE OF THOSE RETURNED SHARES WOULD DEPEND ON THE RESULTS OF THE
      ON-THE-JOB TRAINING OF FANT AND HIS NOMINEES.
 
    - In Fant's July 14 newspaper advertisement, he states that "To take
      advantage of this offer, you must tender your shares and return the GREEN
      proxy card, if you have not done so already." THAT IS A BLATANTLY
      MISLEADING STATEMENT. YOU DON'T NEED TO RETURN THE GREEN CARD TO TENDER
      YOUR SHARES. If you tender your shares, you will be treated the same as
      all other tendering shareholders, NO MATTER HOW YOU VOTE. In his July 15
      letter to shareholders, Fant himself, contrary to his misleading ad,
      admits that: "You are not required to vote your proxy card to tender your
      shares." We believe that Fant was required to make this admission.
      Unfortunately, not all of his misleading statements have been corrected.
 
    - The Company's performance has been very successful under current
      management, resulting in increases in net equity from $1.1 million in
      fiscal 1990 to $17.5 million at May 30, 1998, in annual revenues from $8.5
      million in fiscal 1990 to $31 million in fiscal 1997 and in annual pre-tax
      earnings from $100,000 in fiscal 1991 to amounts ranging between $2 and $4
      million in each of fiscal 1992 through 1997. Revenues for the first nine
      months of fiscal 1998 (ending May 30, 1998) were $14.7 million and pre-tax
      earnings for that period were $647,000 (negatively affected by $274,000 of
      expenses incurred in response to Fant's quest for control). Fant's
      repeated assertions that average annual earnings have declined
      dramatically during the past five years are astonishing in view of this
      performance.
 
    - When the motives for increasing the price of his already oversubscribed
      partial tender offer were questioned by a highly reputable local
      securities analyst, Fant responded with a personal attack on the analyst's
      motivation. This behavior, combined with Fant's repeated maligning of
      HEI's management and performance record, could damage HEI's ongoing
      reputation and its relationship with securities analysts and brokers,
      should Fant succeed in his takeover attempt.
 
    - THE ADDITIONAL COST TO FANT OF HIS "INCREASED" OFFER IS ACTUALLY LESS THAN
      HIS ANTICIPATED EXPENSES OF HIS CONTROL ATTEMPT--EXPENSES THAT HE WILL
      CAUSE HEI (AND THEREFORE YOU, INDIRECTLY AS AN HEI SHAREHOLDER) TO PAY IF
      HE TAKES CONTROL. Those expenses include the numerous expensive ads and
      repeated telephone calls that you have been badgered with. HE SAYS THESE
      COSTS, TOGETHER WITH ALL OF HIS PROXY SOLICITATION EXPENSES, ARE EXPECTED
      TO EXCEED $500,000.

July 17,1998
 
Page 2
 
    - Why is Fant persisting with his disturbing tactics? WE BELIEVE THAT HE IS
      FOCUSED ON HEI'S $13 MILLION CASH RESERVE, OVER WHICH HE HOPES TO ACQUIRE
      CONTROL BY PAYING LESS THAN $8.7 MILLION.
 
    If Fant is willing to use such tactics and spend so much money, he
apparently believes the stock is worth much more than he is paying for it. If
so, why would you sell any shares to him? Do you believe that he will run the
Company better than existing management? What do you know about him? Consider
his tactics. Consider his background and experience. After doing so, we are
confident that you will support your current board of directors by voting
AGAINST Fant's proposals (Proposals 1 and 3) by signing, dating and returning
the enclosed WHITE proxy card in the postage-paid envelope provided.
 
    REMEMBER, NO TENDERED SHARES HAVE BEEN PURCHASED BY FANT AND YOU HAVE EVERY
RIGHT TO VOTE ANY TENDERED SHARES FOR YOUR DIRECTORS AND AGAINST THE FANT
PROPOSALS WITHOUT AFFECTING THE VALIDITY OF YOUR TENDER.
 
Thank you for your support.
 
HEI, Inc. Board of Directors
 
    Robert L. Brueck     Eugene W. Courtney    William R. Franta    Frederick M.
                                                                       Zimmerman
 
    IF YOUR SHARES ARE HELD IN THE NAME OF A BANK OR BROKER, ONLY THAT
ORGANIZATION CAN VOTE YOUR SHARES. PLEASE DIRECT THE PERSON RESPONSIBLE FOR YOUR
ACCOUNT TO EXECUTE ON YOUR BEHALF A WHITE PROXY CARD WITH A VOTE AGAINST
PROPOSALS 1 AND 3 AND FOR PROPOSAL 2.
    IF YOU HAVE ANY QUESTIONS OR REQUIRE ANY ASSISTANCE, PLEASE CONTACT OUR
PROXY SOLICITOR:
                           Innisfree M&A Incorporated
                            Toll Free--1-888-750-5834
                               501 Madison Avenue
                                   20th Floor
                               New York, NY 10022

                                                                       Exhibit 9
 
                                                                    NEWS RELEASE
                     --------------------------------------
 
      [LOGO]
                     --------------------------------------
P. O. Box 5000
Victoria, Minnesota 55386
(612) 443-2500
www.heii.com
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CONTACT:  Eugene W. Courtney, C.E.O.                       FOR IMMEDIATE RELEASE
 
                  HEI SAYS THAT BIDDER'S INCREASED OFFER PRICE
                           IS AN ATTEMPT TO BUY VOTES
 
VICTORIA, MN (July 17, 1998) HEI, Inc. today filed an amended Schedule 14D-9
with the Securities and Exchange Commission containing its response to the
announcement by Fant Industries Inc., wholly owned by Anthony J. Fant, that Fant
is raising the purchase price in his offer to purchase 11.5% of HEI's
outstanding shares from $8 to $9 per share. The HEI Board determined that Fant's
offer, as modified, and quest for control of HEI are not in the best interests
of HEI or its shareholders and renewed its recommendation that shareholders not
tender into the partial offer.
 
Eugene W. Courtney, HEI's Chief Executive Officer and a director, commented:
"This latest tactic appears to the Board to be merely an attempt to buy the
votes of shareholders who are not satisfied with Fant's sketchy disclosures
about his past and vague promises for the future. Fant's amended offer really
has nothing to do with acquiring more shares--based on Fant's recent figures, an
HEI shareholder who tendered 100 shares would get 68 of those shares sent back
without any payment whatsoever. The Board is deeply concerned that Fant
continues to be unwilling to pay a control premium for all shares.
 
"Despite the distraction caused by Fant's tactics and frivolous litigation,
HEI's Board, management, and other employees are committed to the company's
future growth and diversification. We continue to urge shareholders to vote
against Fant's proposals at the Special Shareholders Meeting on August 4, 1998."
 
HEI IS A MINNESOTA-BASED COMPANY SPECIALIZING IN THE DESIGN AND MANUFACTURE OF
HIGH PERFORMANCE ULTRAMINIATURE MICROELECTRONIC DEVICES AND HIGH TECHNOLOGY
PRODUCTS INCORPORATING THOSE DEVICES. THE COMPANY'S STOCK TRADES ON THE NASDAQ
NATIONAL MARKET UNDER THE SYMBOL HEII.
 
FORWARD LOOKING INFORMATION
 
INFORMATION IN THIS NEWS RELEASE WHICH IS NOT HISTORICAL INCLUDES
FORWARD-LOOKING STATEMENTS MADE PURSUANT TO THE SAFE HARBOR PROVISIONS OF THE
PRIVATE SECURITIES LITIGATION REFORM ACT OF 1995. ALL OF SUCH FORWARD-LOOKING
STATEMENTS INVOLVE RISKS AND UNCERTAINTIES INCLUDING, WITHOUT LIMITATION,
ADVERSE BUSINESS OR MARKET CONDITIONS, THE ABILITY OF HEI TO SECURE AND SATISFY
CUSTOMERS, THE AVAILABILITY AND COST OF MATERIALS FROM HEI'S SUPPLIERS, ADVERSE
COMPETITIVE DEVELOPMENTS, CHANGE IN OR CANCELLATION OF CUSTOMER REQUIREMENTS,
AND OTHER RISKS DETAILED FROM TIME TO TIME IN HEI'S SEC FILINGS.
 
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