Technics ST-S7 tuners - best caps to use? is AN6552 an opamp output

Discussion in 'Tuners' started by Synchro-bias, Jan 1, 2018.

  1. Synchro-bias

    Synchro-bias New ClassA

    Messages:
    641
    Location:
    Australia
    I have matching ST-S7 tuners in black and silver for my 2 V8 amps. The displays were dim on purchase and i assumed it was due to failing and aging display.

    I decided to take a look and in both tuners exactly the same capacitors had green on their legs, so maybe the caps in question affected the display

    I was thinking of FM caps, to replace just the faulty ones? and with luck there wont have to be any alignment ? i thought silmicII maybe not suit for PSU, or maybe recap the PSU only , fix the other problem caps?

    AN6552 looks like an opamp for output? OPA2604 in place? 2.2uf to silmicII output caps

    green dots failed caps

    technics st-s7.jpg

    st7.jpg

    s7output.jpg
     
  2. 39cross

    39cross AK Subscriber Subscriber

    Messages:
    843
    Location:
    Beverly, MA
    That cap looks pretty bad. FM will be OK. FM is OK in the PS too. You could also use Wima or Kemet 2.2uf film caps instead of Silmics for the output cap replacements.
    Searching AK, i see some people have used the OPA2604, why not give it a try?
     
  3. Synchro-bias

    Synchro-bias New ClassA

    Messages:
    641
    Location:
    Australia
    Thanks for the reply and help 39cross , Would be cold in MA, heard about the big freeze in the US
     
  4. FauxHall

    FauxHall Super Member

    Messages:
    1,457
    I swapped out the output opamp in a Sony St-J75 with that OPA and it was an improvement.

    Note that Mike also added a larger power reservoir cap for the opamp and a small resistor on its feed from the rail to limit power inrush. He put in a socket so I could swap any number of opamps in.

    Opamps are cheap so rolling them can be a fun sport.
     
  5. 39cross

    39cross AK Subscriber Subscriber

    Messages:
    843
    Location:
    Beverly, MA
    yes it's cold here, -14C at the moment.

    Be sure to use a socket for your opamp as FauxHall mentions.
     
  6. FauxHall

    FauxHall Super Member

    Messages:
    1,457
    It's a bit chilly here in Abu Dhabi too!

    I think the lows are dipping to 65 deg F in the mornings. Days highs are only about 75.

    Tried to swim in the apartment's outdoor pool last night but just too darn cool.
     
  7. Synchro-bias

    Synchro-bias New ClassA

    Messages:
    641
    Location:
    Australia
    Thank you FauxHall - , so any cap near i can increase capacitance, so i will get an adaptor socket to swap but am glad the OPA2604 goes nicely , anything is better than a AN6552 which i have atm. Voltages are pretty low in current 5v max

    Thank you 39cross, shall do, geeze that is cold, been a cold winter, shame our winters in Australia seem to be more on the warm side these winters :(

    That is pretty cool, but not sure if it was the UAE or SA, but there was snow in some mountain town one winter either SA or UAE. ITs all 80 F days here lately though this morning feels nice and cool so running my equipment
     
  8. FauxHall

    FauxHall Super Member

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    1,457
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  9. Synchro-bias

    Synchro-bias New ClassA

    Messages:
    641
    Location:
    Australia

    Thank you Faux Hall, i forgot to get an opamp so used the free postage no min spend at RS
    LME49720 dual opamp , was cheap but min voltage is only 2.5v so is better suited i think to the opa2604
     
  10. FauxHall

    FauxHall Super Member

    Messages:
    1,457
    Here's a cut-and-paste from a 2014 posting of mine

    When Mike refurbished my Sony ST-J75, he pulled the old op-amp (the audio output amp), a NJM4560, installed a socket, and reinserted the old op-amp. He also put in a larger "power tank" electrolytic cap, stacked metal film bypass caps, and a resistor on the line from the rail to the cap to limit in-rush current.

    I've had my local tech order some equivalent op-amps that will fit with his next Digi-key bulk order and plan on some chip swapping once they arrive. Here's the ones I ordered and their catalog prices:


    Texas Instrument OPA 2134 $3.42

    http://www.digikey.com/product-detail/en/OPA2134PA/OPA2134PA-ND/254686

    Analog Devices OP275 $2.71

    http://www.digikey.com/product-search/en?mpart=OP275GPZ&vendor=505

    Texas Instruments LME49720 $3.07

    http://www.digikey.com/product-detail/en/LME49720NA/NOPB/LME49720NA/NOPB-ND/1647708

    Texas Instrument LM4562 $3.07

    http://www.digikey.com/product-search/en?mpart=LM4562NA/NOPB&vendor=296


    STMicro LM833 $0.59

    http://www.digikey.com/scripts/dkse...=1&stock=1&quantity=0&ptm=0&fid=0&pageSize=25
     
    Synchro-bias and FileFixer like this.
  11. Synchro-bias

    Synchro-bias New ClassA

    Messages:
    641
    Location:
    Australia
    The LME883N is in both my Techhnics mash cd players, sound very nice in stock form though the output is just a BA4960 or something like that, i changed them for LME48960 and the other player OPA1642 fet

    Nice choice there, will be interesting to hear the results, i got my LME49720 today, wasnt good prices but 5.63 or something about RS but shipping was free :D

    That says having to spend 60 to get free post that is nice of your local tech to do that, mine was good like that also we are friends now, and he makes DACs and out of repairs.

    Sounds some interesint mods to your sony outputs. I can see the last capacitors in the signal path 180ohm and 3.3 K, wouldve been nice to try Dale Resitors CM-55 s
     
    FauxHall likes this.

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