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Fixing a vintage Tek 465M scope: Bad HV multiplier

Discussion in 'Troubleshooting and Repair' started by mbarrett, Apr 11, 2017.

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  1. mbarrett


    Apr 11, 2017
    My Tek 465M scope HV multiplier has died and I am looking to build (or possibly buy) a replacement, but am confused as to its required specs.

    The HV transformer has a measured ~2.4 KV output to the HV multiplier connection - that is when disconnected from it. The service manual circuit diagram shows the U550 HV box with a X3 multiplier in it. Elsewhere I read that the CRT needs 12-15 KV? and in another place I read that the multiplier is a X6. To further muddy the waters, the NTE538 multiplier is quoted as a replacement but the spec sheet for that unit describes it as a tripler with an input of 12 KV and an output of 30 KV, which calculates as a "2 and a 1/2er". Though I understand why the output may be lower than X3, it implies that with a 2.4KV input the CRT anode voltage would be only 5.6KV.

    Can someone resolve these inconsistencies for me? Sometime before the multiplier was known to be bad I think I saw a DIY multiplier design for this application but now I can't find the link.

    Any information to help bring this old soldier back to life will be appreciated.
    csxvn likes this.
  2. davenn

    davenn Moderator

    Sep 5, 2009
    tekscopes on yahoogroups will definitely be your best bet
  3. 73's de Edd

    73's de Edd

    Aug 21, 2015
    Sir mbarret . . . . .

    Well I’m certainly happy with my TEKS models 465, 475 and 466 Storage and 454 and a Lil Tek/Sony 314.
    Fortunately, with my never having had any HV failures on any of them.
    IF you can now /still even find any HV blocks of that units particular . . . .

    HV Module / multiplier ,
    Murata MSL8521
    Do expect a pretty price.

    My repair choice would be to go with one particular version of the multitude of HV blocks used on
    days of past for Tee Wee kine tubes.
    To wit the NTE 538
    Still being available in fierce quantities, since LCD technology obsoleted kines and their HV supplies.

    Here is a drop in procedure using one HV diode and 1 or two ceramic HV caps along with one of
    those ‘538’s.

    From OLD to NEW



    73’s de Edd
    Last edited by a moderator: Apr 11, 2017
  4. SergioF


    Aug 30, 2020
    Hi Michael:

    Have you find some solution? I have a 465M with the same problem.

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