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AOR AR2000 Radio Fault

Discussion in 'Troubleshooting and Repair' started by zenno, Feb 7, 2019.

  1. zenno

    zenno

    22
    2
    Feb 7, 2019
    Hello folks.

    I have a problem with this AOR AR2000 radio. When I turn it on the audio works good for around 8 minutes, then it causes a buzzing sound and then cannot receive any audio at all, and the radio itself still has perfect functionality except for the audio. When I turn the radio off and straight back on, it works fine again for 8 minutes and then fails again.

    I only use this radio on batteries. Could this be an internal amp problem, or a capacitor problem ?. one more thing is that when the radio is off and left over-night the radio when powered on the next day lasts around 35 minutes working perfectly and then fails after this 35 minute period. Link of the problem is on video below on google drive. Thanks for any help you can provide in regard to which component would cause this particular problem.

    https://drive.google.com/file/d/13p8-IK6Bhjyd6WIcfM7K9uI4NSr1q92g/view


    Michael.
     
  2. Bluejets

    Bluejets

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    Oct 5, 2014
    What batteries are you using and which ones are recommended in your owner manual?
     
  3. zenno

    zenno

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    2
    Feb 7, 2019
    From the manual it say's the receiver is powered from 4xAA high capacity rechargeable NiCad batteries, but I don't have rechargeable batteries at this time so I just use 4x Philips AA Alkaline batteries. The rechargeable batteries are charged by a nominal 13,8 volt dc charger adapter of which I don't have at the moment. I was given this radio from a friend and he didn't have the rechargeable batteries or charger for it. I assumed that using Philips 4x AA Alkaline batteries would be ok. Thanks for your reply.

    Michael.
     
  4. Bluejets

    Bluejets

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    Oct 5, 2014
    Alkaline .....maybe or maybe not.
    Specs say the radio draws approx. 100mA but there are many "if's" that crop up there as to how long Alkaline will last.
    According to many sources, no where near as long as a NiCad charge of supplied cells.
    In fact it is quoted that the NiCad may last up to 4 times longer.
    Have you tried new batteries at all?

    Will admit in the video it sounds like a cap discharge when the set goes out but just trying to eliminate the obvious first.
    Manual also says it will run on an external supply of 11 to 15v DC.
    I imagine you don't have the power lead for that either.....???
     
  5. zenno

    zenno

    22
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    Feb 7, 2019
    I tried brand new batteries and the same problem exists. I don't have the power lead adapter for the radio, I might purchase the adapter, but it could be a waste of money if the problem is still there. I'll have to test the capacitors soon to rule them out, but I'm just trying to narrow it down a bit more before I go in and do the testing. It is strange though, I never encountered this kind of problem before as the radio works perfectly well up to the 8 minute mark and 35 minutes long when left turned off over-night. I did have a look the other day at a good few capacitors but they look ok to me, but obviously will need to be tested regardless.
     
  6. davenn

    davenn Moderator

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    Sep 5, 2009

    yeah but they should last much more than 8 minutes ......
    I have the big brother of that one ... the AR8200 MKIII .... 500kc - 3 GHz
    it lasts for many hours on alkaline batteries
     
  7. zenno

    zenno

    22
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    Feb 7, 2019
    Here's a few pics of the charging pcb. The components look in good shape, no bulges on any capacitors I can see, One more thing, I even tried a cpu reset just incase there was a problem with the cpu, that didn't fix the problem though.
     

    Attached Files:

    Last edited: Feb 8, 2019
  8. Harald Kapp

    Harald Kapp Moderator Moderator

    9,213
    1,856
    Nov 17, 2011
    Could this be a thermal issue? How long does the radio operate if you put it in the fridge?

    Another idea is charge slowly building up on a capacitor that somehow disturbs the operation of the radio. That would not be visible, though, unless you could identify e.g. a cold solder joint.
     
    davenn likes this.
  9. zenno

    zenno

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    Feb 7, 2019
    That's an interesting one about the fridge, I'll try that now. I was going to pick up a bottle of freezing spray for electronic components to see if this was the case. any particular cold setting I should use when putting it in the fridge ?.
     
  10. zenno

    zenno

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    Feb 7, 2019
    Well, that was interesting. I done what you said and I took the back off the radio and put it in the fridge so that the cold could get to the pcb and components faster and left it on mid volume on a music station and the radio has not shut down at all. The radio is very cold and just before I put it in the fridge I tested it to see how long till it cut out and it was around the 8/9 minute period. I turned it off and straight back on and left it in the fridge for 30 minutes and it worked perfectly. Was strange sitting there listening to the music while it was in the fridge I have to say.
     
  11. Harald Kapp

    Harald Kapp Moderator Moderator

    9,213
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    Nov 17, 2011
    Now that it is rather obvious that you're dealing with a thermal issue, you can start narrowing down the location using freezing spray. Or simply start by using your built-in thermometer (aka fingertips) to spot the hot spot (pun intended :)).
     
  12. zenno

    zenno

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    Feb 7, 2019
    Very good. I'll have a look soon. I did notice the other day when I felt around on the power pcb and noticed that a three prong field-effect transistor was warm. Picture of the one that was warm is below marked with the red X. I will purchase the freezing spray soon. I'll update when the spray arrives.

    If it is a overheated component of some sort then I wonder why the radio works fine turning it on just directly after the radio fails. When the radio fails and I quickly turn it off and straight back on I wonder why it still works again for a few minutes as it is not given enough time to cool.
     

    Attached Files:

    Last edited: Feb 8, 2019
  13. Bluejets

    Bluejets

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    Oct 5, 2014
    Yes but thought perhaps they were already flat.

    Wasn't mentioned first up.
     
    davenn likes this.
  14. zenno

    zenno

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    Feb 7, 2019
    Yes Bluejets, I should have mentioned that on my first post. Not to worry though. With a bit of luck I might just be able to track the failing component down when I receive the freeze spray. I'll get to the bottom of it eventually as I like this radio, even though it's an old one. I like it I have to say, I'm into vintage radios any-way, always had a soft spot for them, even though this one is not really that old of vintage, it's a hard to find radio I find.

    Michael.
     
  15. Bluejets

    Bluejets

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    Oct 5, 2014
    We had a similar one here before the 2013 flood ......my son is Michael also and he used to listen in on all the air traffic before he was eventually accepted to the RAAF. ( way back now in '92.)
    That declining whine with the pop at the end in the video ( as I said before) sure sounds like a cap failure.
    Hope the freeze spray sorts it......:cool:
     
    zenno likes this.
  16. zenno

    zenno

    22
    2
    Feb 7, 2019
    Thanks for the reply Bluejets. I hope your son is doing well in the Royal Australian Air Force, quite a serious job to have indeed, and I'm sure it would be a world of very interesting action.

    Yes, I first thought that this problem was an electrolytic capacitor but was put off a bit from the whine at the end of failure, wasn't sure on that. I find it a bit difficult to source this freeze spray here in Ireland as folks here have to purchase most electronic stuff from the UK or further afield within the E.U. It's amazing what you cannot get in my county. There is not one electronic component store or anything like it any-more here, but these stores were rife in the 1980's, then dried up thereafter. I'll be waiting a few days for the freeze spray from the Netherlands to arrive here so will update if I track this little feller component down.

    Best wishes
    Michael.
     
  17. Bluejets

    Bluejets

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    Oct 5, 2014
    Air Force days have come and gone........
    Other may want to comment but have you thought about applying some heat?
     
  18. zenno

    zenno

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    Feb 7, 2019
    I see, Bluejets.

    I've heard of the 'Hot & Cold Method' before, but I'm not sure exactly how applying the heat works. I'm handy with the soldering iron and replacing components, but not fully aware on the heating part.

    Ah that's the guy there explaining the 'Hot & Cold Method' I remember this one from a while ago...
     
    Last edited: Feb 8, 2019
  19. davenn

    davenn Moderator

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    Sep 5, 2009
    That's a voltage regulator IC :)

    It's a 7805 variant of a 5V reg .... TA78DL05S

    datasheet ....
    http://pdf.datasheetcatalog.com/datasheet/toshiba/4150.pdf

    a low drop out version

    warm is not a problem ... hot to very hot would be

    using the freezer spray with a nozzle tube, very carefully squirt individual components
    with a time break between to find the heat affected component
     
  20. zenno

    zenno

    22
    2
    Feb 7, 2019
    Opps, I'm still learning. Got that one mixed up there.

    Will do, I'll take my time with that when I get the spray. Thanks.
     
    davenn likes this.
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