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Ft 901 display flashing

Discussion in '"Boat Anchor" & Classic Equipment' started by KH7HI, Oct 4, 2010.

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  1. KH7HI

    KH7HI Ham Member QRZ Page

    Anyone have any suggestions on flashing displat? My Ft 901 develped this problem. i cleaned the contacts on the vco and the pll card. Dont see anything burnt or suspect. How is the best way to test both the vco and pll? any info would be greatly appreciated. Aloha, Pete/KH7HI
  2. N8YX

    N8YX Ham Member QRZ Page


    Is the display flashing on one band or on all bands?

    And what does the display read when it flashes?
  3. KH7HI

    KH7HI Ham Member QRZ Page

    Tnx for your response. Flashing on all bands, frequency does change when i tune up or down the band. BUT no rx!
  4. N8YX

    N8YX Ham Member QRZ Page

    So the display indicates the frequency correctly on all bands but flashes instead of remaining steady, then?
  5. KH7HI

    KH7HI Ham Member QRZ Page

    Yes, Does display correct band/frequency. Flashes and nothing but white noise can be heard.
  6. N8YX

    N8YX Ham Member QRZ Page

    The symptom is one of PLL lock failure.

    The commonality is the band selector switch. Specifically, the wafers which steer control voltages to the PLL and the VCO modules.

    If one individual circuit of the VCO or PLL was out of order it would result in a failure of one band. All of them going at once but still indicating the correct operating frequency leads me to believe that the fault lies with the wiper on the wafer deck which controls the VCO assembly, or in an attendant circuit. Perhaps the PLL assembly control wafer is also in questionable condition.

    Do you have access to the FT-901DM service manual? I will have a look at mine this evening and post details on which switch wafers to inspect. You might start by cleaning all of them with DeOxIt. Apply the stuff sparingly and carefully wipe the wafers with a cotton swab.
  7. KH7HI

    KH7HI Ham Member QRZ Page

    ft 901 frequency display flashing

    Tnx John, this evening i will inspect the bandswitch wafer/contacts. I will download the manual so we will be on the same "PAGE", -Pete
  8. KH7HI

    KH7HI Ham Member QRZ Page

    ft901 flashing display

    Well, no luck with cleaning the wafers w/ Deoxit. I did notice that the display does not flash when i switch to memory mode. Could this point to a problem w/ the vfo itself????
  9. N8YX

    N8YX Ham Member QRZ Page

    If the display changes frequency as you tune it, no.

    If no change, maybe.

    There are a couple more areas that I'm going to have you take a look at. Will dig into my service manual this afternoon and identify some test points.
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