Yamaha TX-1000U No FM Signal

Discussion in 'Tuners' started by mea2112, Apr 12, 2018.

  1. mea2112

    mea2112 AK Subscriber Subscriber

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    Will do on both asap.

    Q83 and Q84 are also bjt's and have the same emitter, collector and base configuration correct?
     

     

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  2. rcs16

    rcs16 Super Member

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    yes, pin-out is shown in the bottom of the schematic, as ECB for the group starting with 2SA1317S ...
     
  3. mea2112

    mea2112 AK Subscriber Subscriber

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    Q83 - 15.16V
    Q84 - 15.16V

    Hopefully, these are sharp enough.
    #1 - Top Right
    #2 - Top Left
    #3 - Bottom Right
    #4 - Bottom Left

    20180504_133906.jpg 20180504_133606.jpg 20180504_133353.jpg 20180504_132835.jpg
     
  4. rcs16

    rcs16 Super Member

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    Missed a bit in the middle, but good resolution. Add to my collection.
    So to conclude, we have the Q83 and Q84 collectors stuck at +15.16V regardless of FM frequency lower and upper display settings of 88.1 & 107.9MHz in PLL/fine-tune mode?
     
    Last edited: May 4, 2018
  5. mea2112

    mea2112 AK Subscriber Subscriber

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    I'll take a few more down the middle.

    No, I didn't do it right the first time. Checked Q83 and Q84 again and this time changed frequency from 87.50 to 108.00. Both Q83 and Q84 showed 7.43V at 87.50MHz and both showed 25.3V at 108.00MHz.
    *Fine-tune mode turned on.
     
  6. rcs16

    rcs16 Super Member

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    Thought so :) this is good, the PLL control is operating properly imo. I believe something faulty in the analog sections, with no signal strength indication, it is RF,IF etc.
    You have 2 antenna i/p's. have you tried both?
    PLL fine tune/set display freq to a known strong signal. Any signal strength indication? trying both ant i/p's, change the antenna i/p selection to match. Also try different IF filter modes, wide/narrow with the different antenna i/p's to see if you can get any signal strength indication.
    Usual first thing to do. Did you measure the DCV supplies, test points are indicated on the pcb silkscreen printing. +12,-12V?
    IC7-16 (LA1266) is the signal strength indicator drive. When tuned to a strong FM signal it should put out some voltage ~1-3V
    To troubleshoot the analog sections, one usually needs some test equipment, RF sig gen, scope etc to inject signals and monitor/trace signals with a scope.
     

     

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  7. mea2112

    mea2112 AK Subscriber Subscriber

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    Yeah, tried both antenna inputs many times and made sure the A/B switch on the faceplate matched up with the antenna input being used. Tried wide and narrow IF filter modes many times also. No signal strength indication of any kind, not even one bar.
     
    Last edited: May 5, 2018
  8. mea2112

    mea2112 AK Subscriber Subscriber

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  9. Punker X

    Punker X Moderator Moderator Subscriber

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    Doesn't this tuner have PAL connectors? Are you using the correct adapters? If you don't have a signal generator and oscope it's probably going to be very hard to troubleshoot further. Wouldn't normally suggest tweaking anything, but since you are already getting nothing. Mark the IF offset and try tweaking it when tuned to a known strong station. The CLS circuit is a touchy adjustment and if misadjusted it can pretty much cause your dead tuner.
     
  10. rcs16

    rcs16 Super Member

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    Good point Mike, I think that they are the same so called PAL FM RF conn as my T-85.
    I replaced mine with "F" as the adapters are questionable
    Some of the the adapter they are selling on eBay are not the correct ones to use. They are RCA plugs and will not fit correctly.
    Back to some basics for which I was making an assumption that it was not a antenna jack issue, but we need confirmation about cabling/plugs for sure.
    Was the tuner working properly at anytime with the existing cabling/plugs?
    Is this tuner a new purchase, first time use?
    Need verification that the antenna connections are not at fault, or we are chasing our tails :)
     
    Last edited: May 6, 2018
  11. rcs16

    rcs16 Super Member

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    The PS testpoints/jumpers are shown in the top right pic, to the left of the label "FM S AMP"
     

     

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  12. mea2112

    mea2112 AK Subscriber Subscriber

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    Here's a picture of the antenna inputs...

    20180506_103741.jpg

    I've been using an adapter like this...

    Leviton_C5055.jpg
     
  13. rcs16

    rcs16 Super Member

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    Your jacks are not the same as on the T-85.
    The adapter you show pictured is for a "F" connector. It looks the same as in the user manual.
    Did the tuner ever work properly with that adapter you show?
    You could try to insert a piece of copper wire that is the same gauge as the center pin on that adapter.
    Could use a short piece of RG-6/U coax, that is stripped back so the center conductor inserts into the center of the connector, shield can touch the outer shell. connect to your antenna.
    Do you feel that the internal contacts are grabbing onto the wire? does it show any signal strenght indication when tuned to a strong local station?
     
    Last edited: May 6, 2018
  14. mea2112

    mea2112 AK Subscriber Subscriber

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    No, it never worked at all from day one. I got the tuner at a thrift store so who knows what the previous owner/owners did to it.
     
  15. mea2112

    mea2112 AK Subscriber Subscriber

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    Thanks
     
  16. mea2112

    mea2112 AK Subscriber Subscriber

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    No, it never worked with that particular adapter. You guys might be onto something. I really have to find/make a correct adapter so the antenna connections can be ruled out.
     

     

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  17. mea2112

    mea2112 AK Subscriber Subscriber

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    I'm gonna look through my junk drawer and see what I can come up with to try. Otherwise, I'll pick up some copper wire and maybe some RG-6.
     
  18. mea2112

    mea2112 AK Subscriber Subscriber

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    Yeah, the internal contacts do feel like they're grabbing onto the wire. No signal strength when tuned to a strong local station.
     
  19. rcs16

    rcs16 Super Member

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    I think he means to mark the pot wiper position on VR17 or I think you can also measure DCV the wiper of VR17, measure at Q72(e). This is the IF offset calibration procedure. If the IF offset is set incorrectly in that it does not match the IF filters, it will affect the tuners operation.
     
  20. Punker X

    Punker X Moderator Moderator Subscriber

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    The IF offset adjustment directly affects the operation of the CLS, If that doesn't work properly you can get this condition. There is also a diode switching matrix that to switch between antenna A and B. Once seen where the diodes were blown. (Lightning maybe). You can jumper across the matrix directly from the antenna jack to front-end.
     

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