The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Dynaco VTA tube amp kits, all Tubes4hifi.com products and all Dynakitparts.com products


    Bad multimeters

    Share

    Bob Latino
    Admin

    Posts : 2414
    Join date : 2008-11-26
    Location : Massachusetts

    Bad multimeters

    Post by Bob Latino on Thu Jan 29, 2015 12:30 pm

    I seem to have more and more Emails from customers about voltages that are "way off"... A USA line voltage at 137.5 volts? I don't think so .. In all cases we find out later that the meter is defective or the battery in the meter is bad - but some DIY'ers will religiously believe that meter even when the reading that they get makes no sense at all ? At the very least, check the (usually a 9 volt) battery inside and see if it has the proper voltage. Get your self a good and reliable multimeter or better yet > Always have TWO meters on hand so that you can check one against the other. I have here three multimeters - A B&K that I use on a daily basis which is accurate, a Fluke 115 that is even more accurate and an inexpensive Chinese meter that I got off Ebay that seems to work well. The Fluke sits in a drawer and is only brought out to cross check with the other two meters. Another thing ... When you buy a meter, it makes good sense to get one that also measures capacitance. (With the amp OFF) taking a few capacitance readings especially of the high voltage system can sometimes tell you a lot about why your amp/preamp is not functioning as it should. OK - enough said ... Sorry if this sounded like a rant but (IMHO) all people doing DIY work should have a reliable meter and a back up meter to cross check readings if the readings seem wrong ...

    Bob

    wildiowa

    Posts : 126
    Join date : 2012-03-19

    Re: Bad multimeters

    Post by wildiowa on Thu Jan 29, 2015 1:25 pm

    "Interesting/Unique Uses for Multimeters" - My 90 year old mother recently had a raccoon problem that could not be solved. I got a pretty beefy electric livestock fencer for her back deck and we had no more raccoon problems after they got lit up a couple of times. I did make the mistake of checking the fence wire with my multimeter to see if it was functioning after setting it up and needless to say that meter is no longer with us. I don't know how many volts are in those things I thought 600v would be OK but it fried it good. Expensive mistake. A word of caution....

    deepee99

    Posts : 1337
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: Bad multimeters

    Post by deepee99 on Thu Jan 29, 2015 1:54 pm

    Get a Fluke and be done with it.

    sKiZo

    Posts : 1312
    Join date : 2013-04-01
    Location : Michigan USA

    Re: Bad multimeters

    Post by sKiZo on Thu Jan 29, 2015 3:42 pm

    Another option, and yet another great tool for the crib, is a Kill-A-Watt meter ...



    Good for cross checking the AC side of a VOM anyway ...

    All bets are off if you're still using an analog meter. Those are only accurate within a small range of needle movement due to parallax error. The farther you go from the set level listed in the specs, the less accurate. Pegging the needle when using the wrong range doesn't help either. This holds true even for the TOTL meters to a certain degree. A digital meter is also way more forgiving when it comes to polarity or range ooPsies.

    And yes, a couple quality meters are handy to have for cross checking other ranges. For good middle of the pack meters, try Tenma ...

    Some other quickie checks to use ... If you set the DMM to ohms and touch the probes that came with the meter together you should see something less than 0.5 ohms. On the DC volts input a fresh AA or C battery should measure 1.3 to 1.6 volts. As mentioned, plugging into home AC isn't all that accurate as that can be all over the place depending on time of day and system load.

    PS ... if you really want to ensure accuracy, set one multimeter aside as a multimeter tester. You can test that with a multimeter tester tester, and test that with a multimeter tester tester tester. Just to make sure you've not had a tester go bad during the testing, you should then backtrack, testing the multimeter tester tester tester with the multimeter tester tester and then test that with the multimeter tester, and finally one last crosscheck using the multimeter to test the multimeter tester.

    Repeat as needed ...  clown

    deepee99

    Posts : 1337
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: Bad multimeters

    Post by deepee99 on Thu Jan 29, 2015 6:22 pm

    Or just do the tongue-test across the mains. That will verify current.

    sailor

    Posts : 269
    Join date : 2011-04-04

    Re: Bad multimeters

    Post by sailor on Thu Jan 29, 2015 7:40 pm

    Suckered my wife into licking a 9 volt battery, but only once. Twenty years later and she hasn't forgot. Any time I ask her to do something she isn't sure about she says: Not another 9 volt test is it?
    I use my kilawatt on a regular bases. Not only is it very accurate on the voltage but most important it makes it simple to see how many watts are being consumed. I just used it yesterday to find out what the different TV's in the house were using.
    One last thing, if you use your multimeter to test capacitors check the cap first with the volt setting to make sure it is completely discharged or you may fry the capacitor section of your meter.

    audiobill

    Posts : 270
    Join date : 2014-03-13
    Location : Philadelphia

    Re: Bad multimeters

    Post by audiobill on Thu Jan 29, 2015 7:59 pm

    For those interested, take a look at the Tenma 10410, now 60% off at MCM.

    sKiZo

    Posts : 1312
    Join date : 2013-04-01
    Location : Michigan USA

    Re: Bad multimeters

    Post by sKiZo on Thu Jan 29, 2015 8:09 pm

    sailor wrote:One last thing, if you use your multimeter to test capacitors check the cap first with the volt setting to make sure it is completely discharged or you may fry the capacitor section of your meter.

    ... and ALWAYS use any special test leads provided with the meter to minimize any error. My Tenma came with some high grade shorties just for that.

    audiobill wrote:For those interested, take a look at the Tenma 10410, now 60% off at MCM.

    Great price! And a reminder to familiarize yourself with your equipment. I've had my Tenma for years and just noticed a "new" feature when I went to check the price. It's does temperature! Had to dig some to find the box, and found the special probe. Which of course doesn't look anything like what's pictured in the manual, so I've got an excuse for not knowing what it was. And not really needing it, not really caring what it was ...

    Cubdriver

    Posts : 68
    Join date : 2014-01-21
    Age : 51
    Location : Southeastern Litchfield Co, CT

    Re: Bad multimeters

    Post by Cubdriver on Fri Jan 30, 2015 3:36 pm

    sKiZo wrote:PS ... if you really want to ensure accuracy, set one multimeter aside as a multimeter tester. You can test that with a multimeter tester tester, and test that with a multimeter tester tester tester. Just to make sure you've not had a tester go bad during the testing, you should then backtrack, testing the multimeter tester tester tester with the multimeter tester tester and then test that with the multimeter tester, and finally one last crosscheck using the multimeter to test the multimeter tester.

    Repeat as needed ...  clown

    So you expect me to buy a bunch more meters, Skiz? What, do you have stock in Fluke? Razz

    -Pat

    deepee99

    Posts : 1337
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: Bad multimeters

    Post by deepee99 on Fri Jan 30, 2015 3:43 pm

    Nah, he has stock in Radium Shack.
    If he had a Fluke he'd only need one.
    Actually knew John Fluke when he was chmn of a company I worked for in Olympia, WA decades ago. Meanest SOB I ever met; that's the kinda guy you want building/flying things such as we play with.

    Cubdriver

    Posts : 68
    Join date : 2014-01-21
    Age : 51
    Location : Southeastern Litchfield Co, CT

    Re: Bad multimeters

    Post by Cubdriver on Fri Jan 30, 2015 3:56 pm

    He has Rat Shack stock? We should keep an eye on him, make sure he doesn't jump out of a high window or the like... I still wonder how they're hanging on; they're barely even a shadow of their former selves.

    I lucked out and managed to snag a pair of the Fluke 27s that the Army surplussed a while back on Evil Bay. Nice additions to my old 87-II

    -Pat

    Tom

    Posts : 166
    Join date : 2011-04-04

    Re: Bad multimeters

    Post by Tom on Fri Jan 30, 2015 3:57 pm

    So what you're telling me is that the meter
    I got at Advance Auto Parts for $14.95 might be wrong?
    Who knew...
    Embarassed

    deepee99

    Posts : 1337
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: Bad multimeters

    Post by deepee99 on Fri Jan 30, 2015 4:03 pm

    Tom wrote:So what you're telling me is that the meter
    I got at Advance Auto Parts for $14.95 might be wrong?
    Who knew...
    Embarassed
    You could check your tire pressure with it, though.

    Dale Stevens

    Posts : 77
    Join date : 2014-07-06
    Age : 67
    Location : Loris, SC

    Re: Bad multimeters

    Post by Dale Stevens on Fri Jan 30, 2015 5:54 pm

    Recently retire from BellSouth (ATT). My boss offered a retirement party, I said wanted to save the company money just wanted something I had in my desk drawer; agreed! Fluke 189, score. Dale

    tubes4hifi
    Admin

    Posts : 1292
    Join date : 2008-11-30

    Re: Bad multimeters

    Post by tubes4hifi on Sat Jan 31, 2015 1:33 pm

    I haven't had any troubles with inexpensive meters, but ALOT of meters both cheap and not so cheap, are NOT accurate at reading AC voltages.
    Also, I refuse to use an auto-ranging multimeter. I get so many emails from customers with auto-ranging meters that are having troubles reading voltage correctly.
    If you know what the voltage SHOULD be that you want to check, then you also KNOW whether it is AC or DC and what range you want to use.

    GP49

    Posts : 735
    Join date : 2009-04-30
    Location : East of the sun and west of the moon

    Re: Bad multimeters

    Post by GP49 on Sat Jan 31, 2015 7:17 pm

    The biggest pains in the butt for those doing servicing work were the old Radio Shack meters (and others) where you had to change the hot (RED) test lead between sockets to do resistance vs. voltage measurements. You'd be swapping them all the live-long day! Or you'd forget and the reading wouldn't make sense, or the meter would overload.

    Sponsored content

    Re: Bad multimeters

    Post by Sponsored content Today at 7:07 pm

      Similar topics

      -

      Current date/time is Fri Dec 09, 2016 7:07 pm