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Realistic STA-2250 receiver

Discussion in 'Tuners' started by 968driver, Oct 2, 2010.

  1. 968driver

    968driver New Member

    Messages:
    10
    Hi,
    I have a problem with a Realistic STA-2250 receiver.
    After power off, all stored presets of the tuner are cleared everytime.
    I do not find a memory backup battery or capacitor in this unit.
    I also do not have a schematic.
    Any suggestions?
    Kind regards, 968driver.
     

     

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  2. DonQuixote99

    DonQuixote99 just give me some truth

    Messages:
    6,104
    Location:
    Cincinnati, Ohio
    Is your method of power-off to hit an external switch, as on a power strip, as opposed to using the unit's own switch while the power cord remains live?
     
  3. 968driver

    968driver New Member

    Messages:
    10
    Realistic STA-2250 AM/FM receiver

    I use the power switch of the unit.
    The receiver is always connected to the mains.
    If I switch it on again within 10 seconds, presets are still present, after about 10 seconds all presets are cleared.
    All other functions of this receiver work!
     
  4. Copa1934

    Copa1934 My ears are bleeding

    Messages:
    9,841
    Location:
    Great Northwest
    When you say "mains" you are talking about the wall A.C. correct? Assuming you literally sit/stand there and turn it off and then wait 10 or more seconds and turn it back on, then yes you have a Cap/Battery issue. I've looked through almost a dozen RS catalogs and can't find your receiver. What is the catalog number on the back?
     
  5. glen65

    glen65 Member

    Messages:
    4,385
    Location:
    Richland county, Ohio
    1981-83
     
  6. 968driver

    968driver New Member

    Messages:
    10
    Realistic STA-2250 AM/FM receiver

    The model number on the back of the STA-2250 is: 31-2095.
    Could this be the catalog number?
    There is a big and a small power transformer inside. For a moment I supposed the small one is the stand-by transformer and this could be defective.
    However, this is not the case. When I disconnect the small transformer, the fluorescent digital readout is dark.
    So the small transformer is O.K.
    What I really need to solve this one is a schematic.
    Thanks for any help!
     

     

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  7. glen65

    glen65 Member

    Messages:
    4,385
    Location:
    Richland county, Ohio
    Yes, that's the catalog number.


    Yes, a service manual would help, but couldn't locate one.
    Maybe someone else here has one.

    Can you post some good quality pics of the microprocessor area?
     
  8. MAXZ28

    MAXZ28 Addicted Member

    Messages:
    6,517
    Location:
    Springfield, MO
    I would think if there was a battery/cap for presets it would be located on the tuner board. I'll check my STA-2250 tonight.
     
  9. glen65

    glen65 Member

    Messages:
    4,385
    Location:
    Richland county, Ohio
    Thank you,
    He said he checked and there wasn't one present, but
    something has to be there to hold the memory.
     
  10. 968driver

    968driver New Member

    Messages:
    10
    Realistic STA-2250 AM/FM receiver problem solved!

    Hi,
    today I fixed the problem without having the unoptainable service manual.:yippy:
    In this receiver, there is no backup battery and no backup capacitor.
    However, on the microprocessor board, there is, near the microprocessor, a 1000µF/10V elco.
    When desoldering this elco, one of its wires was disconnected from the body (apparently by some chemical action).
    Visually, nothing was giving a clue to this situation.
    After replacing this elco, station memory is sustained.
    On the same board, I replaced another 1000µF/10V elco, the value being decreased to about 100µF.
    I also replaced some other elco's.
    Visually, nothing seemed to be suspected. No bulging, no fluids escaping.
    To me, it seems to be that the elco's in this receiver are not high quality types. It is my experience that quality Japanese audio gear does not suffer from bad elco's, even after 30 years!
     
  11. AnalogDigit

    AnalogDigit Realistic fan.

    Messages:
    7,820
    Location:
    Des Plaines, IL
    Don't you love it when it's an easy fix? Congratulations on fixing the receiver.
     

     

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  12. glen65

    glen65 Member

    Messages:
    4,385
    Location:
    Richland county, Ohio
    Good deal :thmbsp:
    Apparently they used non volatile memory (eprom probably).
    The bad caps you found were keeping the processor from writing
    to the memory.

    At some point you will probably need to do a full recap of the unit.
     
  13. dennis57

    dennis57 New Member

    Messages:
    15
    sta-2250

    i have 2 of these units myself, i totally re-capped them both and the difference is astounding, one ive had from new the second i purchased as a re-build project, apart from the recapping and adding some multi-turn vr's to fine tune the bias on the amp board ive had to do nothing else they perform like gems :)...i do have the service manual for this amp, and will be happy to scan and post it if theres still interest in this unit .:music:
     
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  14. DonQuixote99

    DonQuixote99 just give me some truth

    Messages:
    6,104
    Location:
    Cincinnati, Ohio
  15. dennis57

    dennis57 New Member

    Messages:
    15
    sta-2250

    thnx for the welcome :D, ill post the manual soon as ive scanned it then, its in mint condition so should make a good copy.....i personally wont buy any equipment bar none if i cant get a service manual with it , one day be it 20 plus years later they sure come in handy
     
  16. bierbier

    bierbier New Member

    Messages:
    12
    I just purchased a STA-2250 from Ebay for $20 plus $40 shipping. Output was a little low on the right channel, a recap of the power amp board fixed that issue. I like the way the left and right inputs from the preamp section are in plain view, this enabled me to do some quick troubleshooting [preamp vs power amp].
    Now I am looking for a manual or schematic. I would like to double check the bias settings on the output transistors. Also the memory's are not holding, I am going to replace those capacitors suggested earlier in the thread [Thanks for that info].
    Any additional info appreciated. Yes I will eventually replace all those darn electrolytics.. :)
     

     

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  17. DonQuixote99

    DonQuixote99 just give me some truth

    Messages:
    6,104
    Location:
    Cincinnati, Ohio
    Hmmm. Dennis57, on previous page, said he had the manual you need, but i don't see it in the AK database yet. I've PM'd Dennis to see if he uploaded it or not yet.
     
  18. dennis57

    dennis57 New Member

    Messages:
    15
    hi guys, sry ill have it uploaded soon as i can :)


    * memory not holding try replacing C827 (4700uf 10v) on the controller board :) (its the largest cap on that board)
     
  19. dennis57

    dennis57 New Member

    Messages:
    15
    * idle current .......adj voltage across emitter resistors R541(VR501= LCH) & R542(VR502=RCH) to 10mv +/- 2mv (8 ohm Load),


    * selector switch set to aux

    * mode set to stereo
     
    Last edited: Feb 10, 2013
  20. bierbier

    bierbier New Member

    Messages:
    12
    STA-2250 info Thanks!

    Thank you very much for the information on idle current and memory storage cap. I will do my part also and scan and upload a copy of the SA2000 and TM1001 service manuals.

    Regards,

    GC
     

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