Passenger Intercom

Discussion in 'Electrical' started by MississippiHog, Jan 3, 2009.

  1. MississippiHog

    MississippiHog Member

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    Here is a stumper for ya!

    So far the Intercom system, passenger has burned out two IMCCOM Headset voice coils.

    The front, works great.

    Bike: 2002 Harley Road Glide, factory intercom, 7 pin connections front and back. Controller is tank mounted for setup etc.

    :57:

    Ok, since there has been numerous views but no replies, let me ask this to make it simpler. Where is the circuit(s) board or controller that filters the voltage to those connections, is it on the tank or in the radio or both?
     
    Last edited: Jan 3, 2009
  2. NEWHD74FAN

    NEWHD74FAN Experienced Member Retired Moderators

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    My sincere apology for not responding more quickly...

    Questions:

    1) You state voice coils burned out in the passenger headsets, are they actually showing heat damage (enamel wiring changed color from clear or brown copper color to blackened varnish color)? If black, DC Current probably cooked the windings...check for short circuit/power wiring cross connections. Also use an ohmmeter and check to see if you have any series capacitors that are shorted, they block DC but pass the AC (audio). You are looking for a shorted capacitor or damaged driver output transistor/pass element. Be aware in todays "disposable electronics world" you p-com speaker drivers, plus possible bad main multi-legged custom IC and would cost more to replace than just getting a rebuilt board or intercom system from the OEM...:small3d002:

    2) What were the circumstances of the failure...just turning it on, no audio...running okay then suddenly nothing? Could have been a surge or extremely hot BASS NOTE, that caused speaker to max mechanical limit, scuffing or grounding out the voice coil wiring to the frame/gap/magnet. :shock

    3) Do you have a rough schematic or block diagram that came with the system, a DMM (Digital Multi-Meter), and basic electronic knowledge? :s

    Just asking, so I can walk you through basic electronics or advanced based on your response. :hii
     
    Last edited: Jan 4, 2009
  3. dangerdan

    dangerdan Junior Member

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    This may not apply, but its worth mentioning. My 95 manual says not to mix helmet speakers 77125-88 or 77126-88 or 77147-91

    Reason - The impedance rating is different.

    ARE THE FRONT AND BACK UNITS THE SAME ??
     
  4. MississippiHog

    MississippiHog Member

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    No Same model

    IMC Motorcom by Benchmark Helmets

    Roger that, will await your steps and thanks!
     
    Last edited by a moderator: Jan 5, 2009
  5. NEWHD74FAN

    NEWHD74FAN Experienced Member Retired Moderators

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    It may be relevant in that speakers rated at 4ohms are half the resistance of an 8ohm rated speaker so if your amplifier expects 8ohms, but saw 4ohms it could damage the output stage of the amp (i.e. 1/2 the resistance it should have). Common mistake, some guys think that if they use 4 ohms speakers, calculating with Ohm's Law formula that would increase output power...but extra power is in heat, rather than audio power (mismatched load) heating drivers and voice coils not necessarily making deeper louder sound. :(

    Now it is making more sense, it is the microphone and not the speaker "receiver". What type of microphone is being used,

    "Electret" - basically a DC bias voltage energizes a field, when person speaks the metallic piezo elements "modulates" DC bias with audio energy captured by a very sensitive "front end receiver/driver" with DC bias blocking circuitry.

    "Dynamic Mic" - basically a "speaker in reverse", when person speaks, mylar plastic diaphram w/ voice coil vibrates in a magnetic field, creating energy captured by a modestly sensitive front end receiver/driver".

    The dynamic type is pretty robust and would be only burned out if actual 12V battery or other power cross occured in the headset/amplifier wiring. The Electret type is not so rugged in that if something minor goes wrong or static discharge hits the small DC voltage which may be low 5 to 7V may suddenly breakdown and present the full 12V killing both the mic and the sensitive pre-amp.

    If you have it apart (the Amp and/or the Mic) please determine who the maker is...you may have to Google the vendor/OEM (Original Equipment Manufacturer) for details on replacement parts. Electronics is not easy, just rather tedious...:28:
     
    Last edited by a moderator: Jan 5, 2009
  6. MississippiHog

    MississippiHog Member

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    Sorry, I thought I stated that twice....

    IMC Motorcom by Benchmark Helmets, located in CA. I have not torn it apart to look at the mic and do not plan on it since I would not know what I was looking at to begin with. I would rather look for the issue that caused the exact same failure of both headsets mics. The mic is not accessible since it is sonic welded and taking it apart would more than likely damage it to the point of of rendering its clarity while in use null.

    I do remember in talking to the rep and he did mention it being a dynamic.

    In speaking of that, "What if" the 7 Pin connector from the headset was forced in upside down into the connection on the bike. The standard pin out on the 7 pin, which would be the Tab, then "shared MIC" at position 1. Then the only other MIC pos is 7 which is PTT

    Understand, at the time they failed, my wonderful dearly loved blond from hell is the one that plugged it in, both times.....Just exploring all options.
     
  7. NEWHD74FAN

    NEWHD74FAN Experienced Member Retired Moderators

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    Those Euro Din connectors "fit kinda sloppy" and can be forced enough to misregister pins improperly or crush them altogether...if you/she somehow got reversed polarity with common or momentarily shorted the output + & - not likely did not damage the mic, BUT if you connected the output speaker to the sensitive mic input it could conceivably backflow volts into a millivolt (1,000th of a volt) input, damaging the mic input.

    Dynamic speakers and microphones are pretty robust. Put your DMM on ohms (Rx1 scale), put your ear near the microphone and measure resistance...you should hear a faint click (a dynamic microphone works poorly as a speaker), but click tells you it is working and at same time measure the base impedance of the mic. If no click or ohm reading, it is burnt open, the mic windings somehow got raw 12V momentarily across the coil, smoking it.

    Don't be too hard on your beloved...most manufacturers moved away from the light duty Euro-Din type connector because of the problems. I suppose you could take apart the Din connector and swap mic connections (if they past the test above) between rider and co-rider and see if problem switches to confirm mic preamp(s) are working.
     
    Last edited: Jan 6, 2009
  8. MississippiHog

    MississippiHog Member

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    NewHD74Fan,

    I did some more investigating. I removed the seat today because the bike would not crank like it has normally. I did a thourogh walk through from bumper to bumper removing the bags, side panels, seat, plugs etc...

    Now keep in mind I have owned this one of a kind custom for about two months and done general things, tire, oil, drive belt check, brakes, crank shaft chain etc...

    What I found disturbed me. First, upon close inspection of the battery, the positive connection was so loose it had been arching to to the lead connection on the battery for some time, to the point the lead was melted down the front of the battery. It surprised me because this battery had been on the bike for over 5 years.

    A full 2/3 of the threads were showing on the bolt that held the positive connection to the battery..

    Second thing I found when removing the plugs, the rear plug wire was so loose it took no effort to remove the wire from the plug. If you would have inverted the bike, the plug wire would have slipped right off. I inspected the plugs under magnification and and it was evident that they functioned normally.

    I traced all the wiring and connections to the rear lights, antenna's and radio and intercom controls, no loose wiring. I did find one group of wiring going to a resistor of which all of them were worn but not compromised.

    Other than what I found, I did not see any compromise of electrical on the bike.

    I am going to however wonder if the connection to the battery would cause a spike that could affect the electrical system. I know it could affect the starter...but could it extend to the most vunerable components of the system such as a mic on a head set?
     
  9. NEWHD74FAN

    NEWHD74FAN Experienced Member Retired Moderators

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    Probably not, as the headset mic is pretty far down the electrical chain, especially if the copper wire windings were discolored or burnt...UNLESS somehow 12V got across the hot & return side, it only takes millisecond surge at 12V to damage the fine wires used in the microphone (made to handle millivolts rather than multiple volts. You can also use a dry cell (1.5V) or DMM on Rx1 ohms scale to "click" check the microphones by grounding - side terminal of mic (off the bike/amp of course) and momentarily touching the + side to + side of microphone wiring...should hear faint "click"...can also test your headsets to see if they are okay also, as stated before.

    Since the mics are dynamic...just find a replacement passenger mic or swap with the working rider' mic and see if the problem switches sides (bad rider mic) or remains the same (bad passenger pre-amp).

    If the rider mic ckt runs the passenger mic properly, you got a bad passenger pre-amp (the good rider mic will not work with passenger pre-amp) in that case).
     
  10. MississippiHog

    MississippiHog Member

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    Well the plot thickens.....

    Today, we were doin a poker run, the second leg was at the local Harley dealership here in Jackson, MS. Upon returning to the bike to head to the third leg, the bike would not even kick over.....dead.

    Talk about luck, we had already done a 20 mile leg from the start position. The Mechanics pushed the door stop into the shop, did a few checks and found that the starter relay had burned out. Replaced...

    Ok at this point? Rolled up to the pumps at a gas station 20 yards from the shop, killed the engine and gassed up. Got back on and nothing. Our friendly mechanics pushed it back into the shop and found that it popped the starter/ignition fuse and now the system relay!

    Wonderful, no my day is getting worse, of all the bikes in the poker run, my wife and I were the only ones to have pairs after the first two stops. :small3d031:

    Ok, fixed yet? Hmmm nope... They rolled it to the door, wife and I got on and poof, nothing, popped the starter fuse again...grrrrrrrrrr


    Well, now its spending the rest of the weekend in the shop till Monday or Tuesday.

    BTW, one of the open circuits goes to the Radio/CB and Intercom and the based accessories switch, i.e. the parade fan on the schematics....

    Ok so far we have smoked a starter relay and system relay three starter ignition fuses..Whats left? EFI Ignition coil, Electronic Control Module and various switches...

    Homer, the Harley God of Jackson MS Harley, whom customized this jewel said, hmmm seems the intercom is a symptom of the bigger issue. But the Battery started it all with the low voltage/high voltage spikes because of the lame brain previous owner whom soldered the positive terminal when he had stripped the threads...

    Sounds like the Starter...

    But all in all, It seems the Battery started the cascade of failures...

    Say the least, I wished the individual whom I bought it from was within arms reach at the moment...it would be a come to Jesus moment.