IFR A-7550 memory battery location ?

Discussion in 'Radio Circuits, Repair & Performance' started by KD0CAC, Oct 16, 2019.

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  1. KD0CAC

    KD0CAC Ham Member QRZ Page

    I do have the manual in pdf , but the memory battery is not mentioned , or I have found yet .
    This is one of my " fix it one of these days " projects .
    It's been a yr. + since I looked this unit , as I remember , it would turn on and act normal , then after a few moments it would freeze-up & be unresponsive .
    Some one in a thread somewhat in the last couple weeks mentioned a similar issue .
    So now I'm on the lookout for the location of the memory battery ?
  2. KA9JLM

    KA9JLM Ham Member QRZ Page

    It may use a battery that is built on top of the IC.

    The IC will be really thick if that is the case.

    Good Luck.

    I think this is it.


    Last edited: Oct 16, 2019
  3. KD0CAC

    KD0CAC Ham Member QRZ Page

    What board is it on ?
    What page , I do have both the operating manual & service manual , haven't found yet .
    Would like to have an idea where I'm going , before digging the IFR out again ?
    On another page / source , I remember some one said that they put in another battery / made some changes , something like not the same battery , but a suitable replacement .
  4. KA9JLM

    KA9JLM Ham Member QRZ Page

    It is near the end of the Maintenance manual. It is on the Control Processor board.

    Last edited: Oct 17, 2019
  5. KD0CAC

    KD0CAC Ham Member QRZ Page

    I am not a fan of pdf's , which is what I have , I guess old-fashion / analog mind ;)
    OK I did track it down .
    But then on the other hand , whoever I got the pdf from , put a note on the board picture , saying something about removing and turning the unit off & on 3 times , some kind of reset / reloading of the RAM U12 , until I look at the board , I'm guessing BT1 is the battery ?
    Like in your 1st , it seems the battery & RAM are separate , I have seen other gear where the battery is inside of the chip , but have gather a SWAG that is not the case here - hope .
    I could have missed it , but did not see this reset/reload instructions anywhere in the text ?
    Me & pdf's , need to find how to put-up pages , it could be hand to others - and also confirm the reset - that was hand written on the page ?
  6. KD0CAC

    KD0CAC Ham Member QRZ Page

    Pulled the board & tested battery 3.02v - so OK


    Again the original issue was after powering up and going through the menu after about 5 min-? the keyboard freezes / cannot do anything with screen display ?

    The boards location is access from the top towards the rear ,

    Attached Files:

  7. KA9JLM

    KA9JLM Ham Member QRZ Page

    If you have not done so, It would be a good idea to re-seat all of the chips that are in sockets.

    IC sockets sound handy, But cause problems, Because over time the IC can creep out of the socket.

    I normally make note of pin 1 then carefully remove the IC and clean the leads then reinsert them. Alcohol is all that is needed for cleaning. Sometimes just pressing the IC back down in the socket does the trick.

    Good Luck.
  8. KD0CAC

    KD0CAC Ham Member QRZ Page

    Like many other products , sometimes there is long known cause of a system , ideally looking for that if this issue , lack of keyboard response .
    I know that is just another possibility , again trying to avoid many maybes , it may not be a common issue with a standard fix , just putting out there in case this is .
    I will put that on the list , I do keep deoxit as my 1st contact cleaner , alcohol & plastic safe contact cleaners .
    Of course that is a good preventive , if not the fix for these in general .

    Oh in my searching , I though I saw some posts by you looking for fixes , did you find a fix and what was the issue ?
  9. KB0MNM

    KB0MNM Ham Member QRZ Page

    It may only apply to the IFR COM-120B, yet I had an indication from one tech that there was an 'hour-meter' timeout circuit located in a difficult-to-examine area behind the front panel. IFR / Aeroflex / Marconi Instruments / General Dynamics may all have some info, and would likely ask a hefty price. Back in the days of ancient Rome, an emperor was known to have killed the messenger bringing unfortunate news. I hope that you realize I am bringing you third-party information, and did not design any circuit in the 7550.
  10. KA9JLM

    KA9JLM Ham Member QRZ Page

    Time to send for calibration ?

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