US Navy Tube tester: Bad meter question

Discussion in '"Boat Anchor" & Classic Equipment' started by KN4SMF, May 28, 2021.

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  1. W9GB

    W9GB Ham Member QRZ Page

    Steve Johnson’s Technology web site has a section dedicated to the
    Weston Electrical Instrument Company (Newark, NJ)

    Weston manufactured a Weston 685 Tube Checker (1939),
    also part of the I-56-A military test set (late 1930s).
    Steve Johnson’s Weston collection,
    includes the Weston TV-4A/U that was included in the AN/USM-3A Test - Tool Set
    built for the US Navy around 1953. It includes the Weston TV-4A/U Tube Tester, a TS-673/U Signal Tracer, a ID263/U RF Probe and various other probes, headphone, and accessories.
    KD0CAC likes this.
  2. K4KYV

    K4KYV Premium Subscriber Volunteer Moderator QRZ Page

    If it boils down to definitely being the meter movement, and nothing else in the circuitry was causing the meter to fail, cobbling together a replacement shouldn't be too difficult. First of all, the meter is made by Weston. Similar size square Bakelite Weston meters are abundant at hamfests and junkboxes. Just figure out the basic movement (1 mA, 10 mA, etc) and find another similar meter with the same full-scale movement. Carefully remove the front case as well as that from the original defunct one. Replace the meter scale with the one from the defective unit, being very careful not to damage the pointer, spring or other parts of the movement; chances are it will fall right in place, a drop-in replacement. Re-assemble the meter and you are all set.

    Over the years I have accumulated collection of panel meters of many descriptions. Many times I have interchanged movements, dial scales and glass faces to repair or custom make the meter I needed. Even drew up a few meter scales of my own to fit an existing instrument.
    N2EY likes this.
  3. KN4SMF

    KN4SMF Ham Member QRZ Page

    Once again pecking away at this problem using the above post by SMoAOM as a guide, here is what I've tested on equipment obviously not optimal. One was the cheap Radio Shack LCD meter as pictured, I got a reading of between .11 and .12 milliamperes which converts to 120 microamperes as the logical choice for a full scale reading by shorting the 2 capacity jacks together in the X10 position. Using my Triplett 630na I come up with 80 microampere.

    Attached Files:

  4. KN4SMF

    KN4SMF Ham Member QRZ Page

    Reconsidering this whole matter, I may be barking up the wrong tree. In an earlier post I attached a photo of the guts of this meter with an arrow pointing to what I have reason to believe could be some kind of wire wound resistor. So all my testing could be all pointless. Finding a replacement meter movement would be unlikely to have that "resistor" in it. And it's just as likely that this "resistor" could be what is burned out or open, NOT the meter coil itself. This problem may not be solvable by internet searching.
  5. KN4SMF

    KN4SMF Ham Member QRZ Page

    I have found a fellow who took apart his TV4A/U tube tester and measured the meter. He reports full scale at 97ma with a 1200 ohm internal resistance. Finding a 100ma meter movement shouldn't be so hard. But likely the figures on internal resistance may not be known, with no way of finding out. So what if I find one of 300ohm internal resistance, for instance. What difference would it make? Is there a way to make it 100?
  6. KN4SMF

    KN4SMF Ham Member QRZ Page

    I meant make it 1200

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