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My new multimeter

Discussion in 'Troubleshooting and Repair' started by (*steve*), Mar 2, 2020.

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  1. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,305
    2,738
    Jan 21, 2010
    Hi everyone, I just got myself a new multimeter!

    IMG_20200302_175211_compress33.jpg

    Isn't it a beauty!

    When I got it, the needle was sticking a little, so I took the cover off and "adjusted" it. It appears the needle was actually bent, so a little, careful, tweak was all it needed to be as good as new.

    It's an Aussie made piece of equipment!

    IMG_20200302_175217_compress44.jpg

    This unit is almost 100% bakelite construction, and is without any breaks or modes replacements.

    The rear looks like this:

    IMG_20200302_175444_compress0.jpg

    It's hard to see, but there's something scratched into the bakelite.

    A C Wilsher
    Blomfield Av
    Bega 7C
    NSW

    And inside, in ink in the bakelite (just as hard to read) is:

    F C Wilsher
    Bega

    So... I got hold of the person I bought it from and asked if that name rang any bells. I got this response:

    It's great to have some history about these pieces of equipment. It makes an item such as this just that but more special.

    Back to the repairs... I noticed that the voltage range seemed ok, but the ohms range was very touchy, with the adjust pot being quite intermittent, and the needle unable to be set to 0.

    IMG_20200302_175801_compress88.jpg

    Here are the innards. The owners name is ink on the tag strip. Under it are the switches and pot.

    Do I see a battery there?

    IMG_20200302_175808_compress80.jpg

    How old is it? How much has it leaked?

    IMG_20200302_175855_compress42.jpg

    Removing a couple of screws reveals the D cell. Can't see any leakage

    IMG_20200302_180136_compress60.jpg

    Well there's the reason! It has a miracle seal! So how old is that battery? Radio shack (trading as Tandy in Australia) opened in 1973, was acquired by another company in 2001 and finally closed in 2011. The battery is at least 10 years old, but I suspect it's much older. So while it's not really old, it's not new either!

    I'm going to replace it with this

    IMG_20200302_180153_compress95.jpg

    Dick Smith was an Australian Company that was also bought by the same company and run into the ground. As they went out of business I purchased a number of these very good cells for almost nothing (under $US1 each).

    So let's uncover that pot. First we remove the tag strip revealing some interesting resistors

    IMG_20200302_180009_compress97.jpg

    Anyone want to guess at the age of this meter?

    Under it is the pot, partially obscured by a resistor of some sort (I think)

    IMG_20200302_180022_compress72.jpg

    And there it is. Can anyone tell me the value of that pot? And why?

    Anyway, a replacement was sourced and fitted

    IMG_20200302_181640_compress78.jpg

    Note the difference in size. I hope there isn't a problem with power dissipation.

    IMG_20200302_182042_compress8.jpg

    Fits nicely, but it's upsidedown

    IMG_20200302_180304_compress40.jpg

    Old, and...

    I IMG_20200302_181939_compress46.jpg

    New. Pity it's not brass, but nobody will see it.

    Ok, now, in the ohms range with the input shorted and the control all the way to the left:

    IMG_20200302_182634_compress85.jpg

    And all the way to the right. The intermittent problem is gone!

    IMG_20200302_182657_compress53.jpg

    But nowhere near zero :-(

    However in the x3000 range with an external 45V power supply, the meter zeros.

    I'm thinking that it's either very sensitive to voltage or some of the resistors have gone high. I'll have to get a non-rechargeable D cell to check that out.

    While I had the 45V power supply (5 x 9V batteries) I compared the meter to one of my digital meters. It seems pretty close on the 50V range.

    IMG_20200302_183442_compress32.jpg

    And on the 10V range (with a single 9V battery) it's also close.

    IMG_20200302_183531_compress7.jpg

    So there's a bit more to do, but getting it going shouldn't be a huge problem.

    I need to check the current ranges and the AC voltage ranges. But not today.
     
    davenn, Harald Kapp and bertus like this.
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,305
    2,738
    Jan 21, 2010
    And I've given it a bit of a clean. Mostly wiping of some dust and grime. It looks a bit better.

    IMG_20200302_211659_compress8.jpg
     
  3. Alec_t

    Alec_t

    2,759
    735
    Jul 7, 2015
    Nice find.
    A bit of delicate bending of the needle will soon fix that :D.
     
  4. BobK

    BobK

    7,674
    1,684
    Jan 5, 2010
    I hope you have a good supply of 45V batteries for those high resistance readings!

    Bob
     
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