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podtronics problem

Discussion in 'Norton Commando Motorcycles (Classic)' started by seattle##gs, Apr 10, 2019.

  1. seattle##gs

    seattle##gs

    Joined:
    Oct 28, 2014
    I tried to measure the output of the podtronics with no luck. I measured the output on the black wire at 9+ volts at idle. When the throttle was turned up it actually went backwards toward zero. What gives?
    The podtronics is connected directly to the alternator. All new wires and connectors.
    the ground wire for the podtronics is connected directly to the battery. Yes, I am using the DC scale. The meter is connected to the black lead the other to ground.
     
  2. gtiller

    gtiller VIP MEMBER

    Joined:
    Nov 5, 2012
    As confirmation of the wiring, and that it's not being caused by a bad earth try putting your voltmeter across the battery positive and negative terminals.
    • With the engine off, and ignition/lights off you'd expect to see around 12 to 13 volts (depending on the type of battery you have)
    • With the engine started and at idle, i would expect to see the voltage at the battery drop to around 11 to 12 volts (showing that you are drawing more than you are charging)
    • At an RPM of 3-4k i would expect to see the voltage go up to around 14 to 15 volts
     
  3. dynodave

    dynodave

    Joined:
    May 28, 2003
    Because of the operation type of the unit, it does not like digital meter that it's normal aliasing mode will give crazy results from the pulse and ac components. An analog meter will not go crazy though you can measure either the dc component or AC/pulse component. Batteries of course ignore all this. Also it need s to be hooked to the battery or a load to get better results.
     
  4. seattle##gs

    seattle##gs

    Joined:
    Oct 28, 2014
    the lights were on while it was running.
    measuring across the battery was approx 12 V and hardly moved when the rpms increased.
    Why did the meter go backwards measuring off of the podtronics output wire?
     
  5. worntorn

    worntorn

    Joined:
    Dec 22, 2006
    As Dave said, digital meters do not work around a running engine.
    The RF interference makes them crazy.
    What kind of meter are you using?

    Glen
     
  6. marinatlas

    marinatlas

    Joined:
    Nov 4, 2007
    Even with a Fluke ?
     
  7. marshg246

    marshg246 VIP MEMBER

    Joined:
    Jul 12, 2015
    A $10 analog meter is superior to any digital meter when working on old bikes. Besides RF problems, the slightly changing voltages make it difficult for a digital meter to settle on a voltage. Even on modern cars, I don't even try digital meters.

    The analog meter I use cost me about $30 from Amazon and it has everything possibly needed for working on bikes including a 1 ohm resistance setting and a 10amp current setting.

    I reserve my Fluke digital meter for working on non-automotive electronics.

    BTW, if you're checking the black wire without it connected into the bikes circuitry, your testing is invalid. Electronic regulators don't work properly without a load.
     
  8. dynodave

    dynodave

    Joined:
    May 28, 2003
    It is not RF interferance is is the sampling rate of the meter that interacts with the variable frequency rectification pulses. The meter is a fixed frequency sample rate(on a particular scale) while the engine runs as a VFD when you work the throttle up and down. They are not synchronized and the technical term is aliasing to describe this mismatched error condition.
    If you build data acquisition equipment with digital/analog converters you must know all about this stuff. While like most cases, I'm not an engineered super expert but while trying setting up my dyno's data acquision equipment, I had a very big dose of these concepts.
     
  9. worntorn

    worntorn

    Joined:
    Dec 22, 2006
    I tried measuring the voltage in a spare battery on the bench using a digital meter with my old Rapide running 3 feet away.
    Got crazy readings with no connection to the bike. Analog in same scenario works fine.
    Pretty sure that is RF interference.
    The shop radio agrees, worse on AM!

    Glen
     
  10. concours

    concours VIP MEMBER

    Joined:
    Dec 29, 2011
    I have an old Simpson analog... somewhere.
    I regularly check AC output from alternators on bikes with my Fluke, and other DMM’s, with never any flaky readings. One of the more memorable was on a cold, rainy day on the Blue Ridge Parkway, I noticed my buddy’s Commando headlight go from white, to yellow, to brown, then he was no longer in my mirror. A $5 Harbor Freight (disposable) DMM confirmed the Sparx stator was faulty.
    I have had no trouble reading the ACV, or DCV on bikes, old or new.
    JMWE
     
  11. seattle##gs

    seattle##gs

    Joined:
    Oct 28, 2014
    I tried both analog and digital meters. The digital was useless. Why did the analog needle go backwards when I turned up the throttle?
     
  12. gortnipper

    gortnipper VIP MEMBER

    Joined:
    Nov 11, 2013
    Polarity.
     
  13. seattle##gs

    seattle##gs

    Joined:
    Oct 28, 2014
    I tried flipping the test leads. even worse
     
  14. gtiller

    gtiller VIP MEMBER

    Joined:
    Nov 5, 2012
    As I said before, do all your testing across the battery terminals.

    The battery acts to smooth out the wild fluctuations which means you can use a digital or analogue meter.
    Although a needle will buffer your readings even more, showing what appears to be a more stable output.

    You need to be drawing a load from the podtronics, or your readings will be invalid.

    You are probably seeing a negative ‘swing’ when the gates in the podtronics circuitry open and close.
     

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