SX-1280 Tuner issues

Discussion in 'Pioneer Audio' started by xratedpez, Mar 27, 2013.

  1. markthefixer

    markthefixer On Hiatus, dealing with Dad's estate full time Subscriber

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    The 1197 is the cheapest chip to replace as a test. Get the AM going, but the universality of the high voltage readings that depart from the called for DC readings indicates severe chip damage.

    The PA1002 will be the hardest to find if it is necessary to replace it.

    The pa3001 FM detector chip and the pa1001 should also be inexpensive since a multitude of x80 series models use them.

    The TA7302P if amplifier chip is also rarer, only being used on the 1080 and 1280.
     
    Last edited: Mar 29, 2013
  2. xratedpez

    xratedpez Super Member

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    Thanks guys. Since I've never worked with ICs before, it's safe to simply swap them out piecemeal, beginning with the AM chip?
     
  3. markthefixer

    markthefixer On Hiatus, dealing with Dad's estate full time Subscriber

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    I'm gonna have to hold your hand on this tuner repair.

    first the AM as proof of concept, then the pa3001 and see if we get the signal and tuning meters working, next the IF strip if we don't. (fm mono will be working internally, but not coming OUT of the tuner when the meters are working)
    after signal and tuning meters, then the pa1001 stereo decoder
    finally the unobtanium pa1002 to get fm sound actually out

    are the old chips getting hot?
     
  4. xratedpez

    xratedpez Super Member

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    Sounds good. I'll work now on getting whatever chips I can, in the order you detailed above.

    Nope- the old chips are not getting hot.
     
  5. petehall347

    petehall347 the brandy coffee man

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    out of interest data sheet for ha1197 says max 15vcc .. would 17v kill it ?
     
  6. markthefixer

    markthefixer On Hiatus, dealing with Dad's estate full time Subscriber

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    Q.E.D. - something killed it, don't know how high the voltage got during the fault.

    If replacing the ha1197 brings back the AM....
     
  7. xratedpez

    xratedpez Super Member

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    Alright- the 1197 chip came in. Will replace tonight and report back. Thanks all.
     
  8. xratedpez

    xratedpez Super Member

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    Ok, chip installed- voltages are now very different.

    If no voltage present, I left it blank.

    AM Chip HA1197:

    Pin# / DCV
    1/
    2/
    3/.052
    4/13.35
    5/13.35
    6/
    7/
    8/3
    9/9.7
    10/
    11/13.35
    12/1.6
    13/0.73
    14/1.56
    15/
    16/

    I have not switched it to AM yet, out of caution.
     
  9. markthefixer

    markthefixer On Hiatus, dealing with Dad's estate full time Subscriber

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    It looks loads better to me. Chip isn't fully powered, but portions are and the voltages that are showing up are reasonable.

    Go ahead.

    I don't wanna jinx it, but I really would be surprised if there were anything other than tuning/alignment issues, and AM alignment bears fruit lots easier than an FM alignment. Also harder to hit the alignment point on the head/sweet spot for BEST performance because the difference between ok and best are harder to discern.
     
  10. xratedpez

    xratedpez Super Member

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    Alright- Fired it up with AM selected, and it seems to be fixed! I can grab some stations and the alignment doesn't even seem too bad upon first glance. Tuning meter works in AM.

    Now for the 3001 chip, correct? FM still has no signal or tuning meter movement, nor audio output.

    Thanks.
     
  11. markthefixer

    markthefixer On Hiatus, dealing with Dad's estate full time Subscriber

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    post voltages for the pa3001 and ta7302

    if you have some way of detecting 10.7 mhz signals, use it. watch it grow and fade as you tune.
     
  12. xratedpez

    xratedpez Super Member

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    Ok, will do. I have a 20MHz scope, what test point(s) should I connect to?
     
  13. xratedpez

    xratedpez Super Member

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    (zero volts = blank)


    IC PA3001A:

    Pin# / DCV
    1/
    2/.638
    3/
    4/
    5/
    6/
    7/
    8/
    9/
    10/
    11/13.34
    12/
    13/
    14/
    15/0.84
    16/


    IC TA7302:

    Pin# / DCV
    1/2.75
    2/2.75
    3/3.77
    4/
    5/6.15
    6/11.67
    7/12.3
     
  14. markthefixer

    markthefixer On Hiatus, dealing with Dad's estate full time Subscriber

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    ta7301 pins 1 and 6
    pa3001 pin 1
     
  15. xratedpez

    xratedpez Super Member

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    You're right-when I tested 3001 and TA 7302 earlier, The FM selector wasn't engaged (AM was). However, I just retested with the selector engaged, and the readings were identical- the only real reading on 3001 is the 12.3v on pin 11.

    Also, I got no signal from the pins you suggested WRT chassis ground.
     
  16. markthefixer

    markthefixer On Hiatus, dealing with Dad's estate full time Subscriber

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    sigh, time for Punker_X and Radio_x_tuners. we gotta find out if the front end is even operating, could be your test equipment, could be the tuner.

    you could try getting those two chips and putting them in and trying again,it can't hurt...

    the ta7302 will be a bit harder to find, as it wasn't used in many models....
    the ta7302's voltages DID look OK, and if there is a WHISPER of 10.7 MHZ coming through the PA3001 WILL give you some indications, so I would start with it first.

    just about any sx-x80 model will suffice for parts donor for the pa3001.
    the pa3001 voltages are wayyyy whacked...
     
    Last edited: Apr 15, 2013
  17. xratedpez

    xratedpez Super Member

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    Alrighty, I replaced the PA3001A chip. Here are the voltages now, with "FM" engaged (I still have no FM audio output).

    IC PA3001A:

    Pin# / DCV
    1/1.92
    2/1.92
    3/1.92
    4/0
    5/0
    6/5.17
    7/5.26
    8/5.61
    9/5.62
    10/5.62
    11/13.33
    12/3.64
    13/0
    14/0
    15/4.96
    16/3.62
     
  18. markthefixer

    markthefixer On Hiatus, dealing with Dad's estate full time Subscriber

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    Those voltages look good, the chip is operating.

    tune to a really dead portion of the FM dial, short all the pins (and strap) on the antenna strip with one short piece of continuous wire, then adjust the lower discriminator core T6 to center the tuning needle. Use a plastic, UNDERCUT (0.xx inch) hex adjustment tool. DO NOT go more than 3 turns in either direction, do NOT loose count, put an indexing flag on the tool!! And if any doubt, return to the exact point you found it at.
    Changing the chip probably threw off the adjustment.
    Leave the upper core alone, that's what the undercut is for.
     
    Last edited: Apr 19, 2013
  19. xratedpez

    xratedpez Super Member

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    Alright- This will be my first core adjustment. I'm confident I have the patience to do it properly, but I want to be armed with the proper tools.

    In researching tools, there are lots of links out to sites that have all sorts of tuner alignment stuff, but I haven't yet found what I'll actually need for this job.

    Does anyone have quick/easy links that I can follow and purchase? Otherwise, I'll keep researching :)

    Thanks!
     
  20. bktheking

    bktheking Gitter Done!

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