Tuner on Sony GX9ES stuck in Japan FM 76-90 mode?

Discussion in 'Tuners' started by reydelaplaya, Mar 30, 2018.

  1. reydelaplaya

    reydelaplaya AK Subscriber Subscriber

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    Just tried this, but sadly didn't work. Thank you though.
     

     

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  2. restorer-john

    restorer-john Addicted Member

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    No. The controller is clearly not changing stepping correctly. We have 9KHz spacing here in Australia. All our stations are divisible by 9KHz and the steps are 9KHz jumps. Stations are 612,972,1008,1134 etc.
     
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  3. reydelaplaya

    reydelaplaya AK Subscriber Subscriber

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    Ok, thank you for clarifying. That at least gives me a better idea of where to look in the schematics. I do know that it has no problem tuning with those same two -/+ buttons though in both AM and FM. I've just pulled off the cover and faceplate to see if I could see anything unusual on that controller board, but no, everything looks normal - no burn/scorch marks, no odd smell, nothing. Even took the extra step to lightly prod at different components on it with a plastic tool while powered up to see if maybe there was some type of poor solder connection, but there again, nothing was resolved or even did anything funny for that matter.

    Only just now put it all back together and am content (read:frustrated) to just leave it before something else stops working. At least the rest of it works properly. Only other thing I can think of is to leave it unplugged for about a month and see if the memory of everything just clears itself out like it says in the manual. (But that would mean leaving my new toy unplugged for a whole month :( )
     
  4. reydelaplaya

    reydelaplaya AK Subscriber Subscriber

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    Well, just got off the phone with united radio. They were not pleasant. A blunt, "None of our technicians work with anything that old. Can't help you. Try the internet."

    Needless to say, nothing resolved there either.
     
  5. dr*audio

    dr*audio Fish fingers and custard!

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    I don't have time right now to look at the manual, but look at the schematic of the processor. Look for a pin that says "Reset." or MCLR. Short it to ground momentarily.with the power on.
     
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  6. reydelaplaya

    reydelaplaya AK Subscriber Subscriber

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    Thank you for your suggestion. Let me just check with you before I do anything. Enclosed are both the schematic from the service manual, and the datasheet info for the UPD75108CW chip.

    The datasheet says that pin 45 is the reset pin.

    DatasheetControl.jpg


    In the schematic, it is unlabeled, but it does lead off to a transistor there at the bottom right corner of the pic.



    control.jpg



    Just to fully clarify before I attempt anything, this is the pin I should short to ground momentarily?
     

     

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  7. jimbofish

    jimbofish for TRULY GREAT MUSIC

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    Yeah, that occurred to me too.:(

    However, even if so, there must have been some provision for changing it from that to US settings, some sort of menu to select the country, like Sony's SW radios have.
     
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  8. restorer-john

    restorer-john Addicted Member

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    Here's the datasheet:
     

    Attached Files:

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  9. reydelaplaya

    reydelaplaya AK Subscriber Subscriber

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    Thank you for providing that permanent link.

    So there on pdf-page 6, the drawing I have above. Pin 45 is the reset. Grounding that is just going to put it back to factory settings (not erase the chip itself)?

    I’m totally cool to pull the cover on this again and try it out. I just wanted confirmation first that this is indeed the correct spot, so I don’t end up irreversibly damaging that chip.
     
  10. reydelaplaya

    reydelaplaya AK Subscriber Subscriber

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    What you say makes sense, and I though so too, but there is nothing in either service/owners manual that refers to the FM side of the dial, only the AM. And as I’ve mentioned above, neither Sony Consumer Support nor Sony Pro/ES support have any idea how to switch it back.
     
  11. audiotemp

    audiotemp Well-Known Member

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    It looks to me like pin 45 of the microcontroller is pulled low at every power up by IC904. Your manually pulling it low isn't likely to do anything additional. On the other hand, the Vdd power pin (pin 32) is held at positive voltage after power off by a combination of capacitors and that is likely how memory state is maintained. C903, C927, and C910 may all be contributing to that. C910 is of the "supercapacitor" type and is probably responsible for long term memory retention. Pulling pin 32 low (maybe through a resistor) with power off might accomplish something equivalent to leaving the unit unplugged for a month.

    There was definitely some wisdom to what you said earlier about quitting when you were ahead, though. Get some other opinions before trying this.
     
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  12. restorer-john

    restorer-john Addicted Member

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    Just pull the Supercap (C910 .1F/5.5v). Leave it out. Power up after 20 mins and see what happens. See whether the 9/10KHz AM step set works too after that.
     
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  13. reydelaplaya

    reydelaplaya AK Subscriber Subscriber

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    Ok, so if I understand you guys correctly, this is the capacitor I'd want to pull from the board for a while to possibly reset the memory completely. Since I now see where it is, next time I've got the case open, I'll see if I can get to it.

    C910.jpg


    [​IMG]

    That bottom pic is from the OP over on that other site (2nd to last post on that page) that I linked to in the 'purchase thread', I now remember that he mentioned that his GX10ES wasn't retaining memory, and he replaced it with that capacitor in the photo (though he didn't explain his reasoning for changing its value). I didn't realise that this would also be possibly forcing mine to retain its current settings.

    I've got a little basic knowledge of electronics at this detail, but certainly not enough to be able to just look at a schematic and a board like looking at a roadmap and be like 'oh yeah, that's what we're looking for...' LOL

    Thank you very much! I do appreciate your patience and help. I'll let you know how it goes once I get that board out of there.
     
  14. dr*audio

    dr*audio Fish fingers and custard!

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    Shorting the supercap was going to be my next suggestion. Try shorting pin 45 to ground first, in case it isn't getting a good reset on power on. If that doesn't work, short the supercap. No reason to remove it and just removing it may not fully reset the memory. Usually that pin draws a very small current so it may maintain it's charge for a while unless it is grounded.
     
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  15. audiotemp

    audiotemp Well-Known Member

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    You know, today pin 44 of that microcontroller is seeming kind of interesting to me, what with the way it is labeled in the schematic (like it has a function of some kind) but is just wired to ground through a resistor (like it has no real function). Kind of makes a person wonder what it might do... :D
     
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  16. reydelaplaya

    reydelaplaya AK Subscriber Subscriber

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    Ok, thank you. When I go to short it, which side gets shorted to ground?(The side electronically closest to pin45, or the opposite?) Or am I just supposed to short its terminals together with a wire or resistor?

    Thank you for your suggestion, but please forgive that I don't completely understand - are you saying that pin 44's resistor may be bad? And beyond that, that resistor may be what tells the controller chip what country it's in? In other words, in Japan, Sony stereos using this same controller chip that resistor may be a different value?

    Coincidentally, the Walkman from around that same era was able to switch on the fly using just an extended keypress and the hidden enter button. http://stereo2go.com/forums/threads...sony-wm-fx822-radio-tuning-to-us-region.2110/ The online service manual isn't clear enough to see the pin labeling on the controller chip to see if it's something even remotely similar to this one though.
     

     

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  17. reydelaplaya

    reydelaplaya AK Subscriber Subscriber

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    FOUND IT!!! :D

    Fellow member @andy had this same problem on his GX10ES waaaaayyyy back in 2004. LOL

    Which a member on a different site (which appears to be him too) managed to figure it out: http://www.edaboard.co.uk/sony-str-gx10es-tuner-in-japanese-mode-t19220.html

    And even then, @dr*audio called that memory cap, too!

    Guess the reason I wasn't finding the answer was that I was too specific about my model number, should've considered that the GX10ES was using the same controller/tuner.

    I love the internet! It's the modern day Library of Alexandria.

    Thank you to you all for helping me with this! Andy, you too, though you're probably only just now figuring out that you've helped me with mine! LOL

    So, for the time being while I'm waiting for a replacement capacitor, would grounding this one at least get me back into US FM?
     
  18. reydelaplaya

    reydelaplaya AK Subscriber Subscriber

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    Shorted that memory cap with a 100Ohm resistor for about a minute, then made sure it was drained by shorting it directly across its pins, and now... wait for it

    We are back in US FM Scale!

    E34A7E18-0C12-4DF9-91B2-62354521ACE2.jpeg

    Awesome!

    Again, thank you to all of you for helping diagnose this! Very much appreciated! Beers and Cheers to all!
     
    Last edited: Apr 6, 2018
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  19. audiotemp

    audiotemp Well-Known Member

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    Congratulations, nice work.
     
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  20. reydelaplaya

    reydelaplaya AK Subscriber Subscriber

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    Thank you, but couldn't've done it without all the help and input from you fellow members here.
     

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