How to fix inaccurate dial?

Discussion in 'Tuners' started by SoundsAlike, May 2, 2018.

  1. SoundsAlike

    SoundsAlike Super Member

    Messages:
    1,835
    Location:
    Greensboro, NC
    Alright — how do I fix a tuner where let’s say a station such as 88.5 is displayed on the tuner’s dial as somewhere closer to 90.5? The dial indicator is off by somewhere close to an inch

    For years I thought this is fixed by “FM alignment” but from what I’ve recently read on FM alignment is that procedure is used to fix FM tuners doing bizarre things like no reception, bad stereo imaging, or the same channel being received at multiple spots along the dial — I’ve never had any of these problems
     

     

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  2. Blue Shadow

    Blue Shadow I gotta get me a new title

    Messages:
    20,172
    Location:
    SE PA
    The positioning of the dial pointer is usually changed by moving it along the tuning cord. This is part of the standard set up for a tuner and if not locked in place with tabs bent down to hold it and/or paint/glue the dial pointer might move a bit when the tuner is used to extremes. Although the correct way to 'fix' this problem is as you say an alignment, if your pointer is off by an inch all the way down the dial, I would think the pointer has slipped on the dial cord. Gotta get in there and look around. Maybe the manual for your unit explains what you need to know to make some adjustment.
     
  3. SoundsAlike

    SoundsAlike Super Member

    Messages:
    1,835
    Location:
    Greensboro, NC
    It's a Marantz 2230, looks to be glued in place -- probably more trouble than it's worth to get it on point
     
  4. dr*audio

    dr*audio Fish fingers and custard!

    Messages:
    18,550
    Location:
    Cleveland, Ohio
    The correct way to do this is by adjusting the local oscillator. Some tuners have only a trim cap to adjust it, some have an inductor for the low end of the dial and a cap for the high end. You go back and forth from low to high until both are accurate. You can adjust them with 2 known stations at near the ends of the dial. You must use a non metallic tool or you will detune the circuit and in the case of an inductor you will break the ferrite core if you use a metal tool. Look in the service manual under the alignment section. It will show you the location of the adjustments. If it only has a cap you adjust it in the middle of the dial. And turn the adjustments only a tiny bit at a time! They are very sensitive.
     
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  5. Blue Shadow

    Blue Shadow I gotta get me a new title

    Messages:
    20,172
    Location:
    SE PA
    Of course, Warren's method assumes the dial pointer is in the correct original position and hasn't moved. My method is for tuners getting new string and positioning the pointer as instructed in a service manual.
     
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  6. gadget73

    gadget73 junk junkie Subscriber

    Messages:
    35,878
    Location:
    Southern NJ
    Right, first step with a tuner alignment is mechanical alignment of the pointer. Usually its easy to see if its out of whack, just run it end to end and see where the pointer stops. The service manual should tell you what it ought to be doing.

    Its not impossible that the wheel on the side of the tuning condenser has slipped on the shaft, which would throw the dial without the pointer having moved on the string. I've seen plastic wheels crack at the hub where the set screws are.
     

     

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  7. steveUK

    steveUK AK Subscriber Subscriber

    Messages:
    446
    Location:
    Midlands, UK.
    The other thing is, when you move the dial pointer along the cord to a new position, you may find that after a few end to end turns of the tuning knob it is slightly off again. This is due to the cord having a 'tight' side and a 'slack' side each side of the tuning knob. So it's a case of making small adjustments until it is more or less correct when turned in each direction. Also, when you have reset the pointer, try 'wobbling' the tuning knob in each direction to even out the play either side of it.
     
  8. tarior

    tarior Dirty pool, old man? Subscriber

    Messages:
    6,482
    Location:
    Kelso, Washington
    dr* audio gave the correct method for aligning the pointer with the dial on a tuner that hasn't had the dial cord replaced. Typically the pointer will be affixed to the cord with bent tabs and an adhesive of some sort. Futzing with trying to separate the two is a good way to end up with a broken cord or dial pointer.
     
  9. steveUK

    steveUK AK Subscriber Subscriber

    Messages:
    446
    Location:
    Midlands, UK.
    It's not unknown for the pointer position to somehow 'get moved' along the cord. It's not difficult for someone with a bit of patience and dexterity to carefully raise a couple of tabs, remove some glue and slide the pointer to the correct position. I've never broken a cord doing that, and I've done many. If the pointer hasn't moved - and the service manual will usually identify where it should lie when the tuning knob is turned fully towards the low frequency end of the scale - then adjusting the local oscillator is indeed the way forwards. But as I explain, depending on the circumstances, the latter is not always "the correct method" to align a pointer. It could have moved due to mechanical issues, it could have moved due to component drift.
     

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