Project: Fisher RS-2010

Discussion in 'Fisher' started by Super Noob, Jan 27, 2019.

  1. Super Noob

    Super Noob AK Subscriber Subscriber

    Messages:
    326
    Location:
    Fort Myers, FL
    Just reached 95% on the RS-2010. Am a sucker for vintage equipment and any unit that hits the triple digits on the WPC. Found this unit local really reasonable about a year ago or so ago. Cleaned up & replaced all the lamps to LED. It sounded nice and decided to send to my father in-law = to give him at taste of vintage gear. Was slightly worried that the STK packs might fail as some point... he purchased some 8 ohm Boston A100 speakers.

    After a few months it stopped working - likely one too many Miller Lites one evening. Since he enjoyed the stereo, I decided to rebuild and give him one of my unicorns (Realistic STA-2100). The Fisher made it back to my hands at the beginning of the month. Turns out that one of STK-0080 was blown - no surprise there.

    RCS16 and others came up with a kit to replace the STK-0050 modules.... and I thought this would be good test bed for the STK-0080 (which appeared to within the realm of the kit) . Bought the kits off fleabay and built them = thanks to RCS16 for his help.

    [​IMG]

    [​IMG]

    [​IMG]


    More post to follow.
     
    Last edited: Jan 27, 2019
    kirkendoll likes this.

     

    Please register to disable this ad.

  2. Super Noob

    Super Noob AK Subscriber Subscriber

    Messages:
    326
    Location:
    Fort Myers, FL
    Power Amp Board:

    Turns out that the left channel took out two (2) diodes, (2) transistors, (2) 3.6 zeners which where consumed in the process. I decided to recap the power board while I had it out. Replaced the toasted parts and could not get sound out of the left channel thought everything measured out good. Followed the sound to the relay = good on one side bad on the the other.

    Relay Picture - think you see the problem:

    [​IMG]

    Picture of the amp board with new discrete STK boards mounted on the heat sinks. They look awesome - had to make some holes. Think it turned out great. Replace the relay and recapped the power board and everything is good. Dialed the bias up by adjusting to 38mV across both .47ohm resistors on each channel equaling to roughly 40mA bias.

    [​IMG]
    [​IMG]
    [​IMG]
     
    Last edited: Jan 27, 2019
  3. Super Noob

    Super Noob AK Subscriber Subscriber

    Messages:
    326
    Location:
    Fort Myers, FL
    Power Supply:

    Did recap this board - will come back here when the final few parts show up next week and put an after picture.

    [​IMG]
    [​IMG]
     
  4. Super Noob

    Super Noob AK Subscriber Subscriber

    Messages:
    326
    Location:
    Fort Myers, FL
    PreTone Board Next

    Before:
    [​IMG]

    After:
    [​IMG]
    [​IMG]

    Usually do WIMAs up to 4.7uF.... but elected to go with UKL on the 4.7uF due the the number and size. WIMA for all up to 3.3uF.
     
    Last edited: Jan 27, 2019
  5. Super Noob

    Super Noob AK Subscriber Subscriber

    Messages:
    326
    Location:
    Fort Myers, FL
    EQ AMP

    Before:
    [​IMG]

    After:
    [​IMG]

    [​IMG]

    It is hard to think how many caps I have replaced in the last 18 months = probably near 1000. First one I found that was clearly vented / fully emptied.
     
    Last edited: Jan 27, 2019
  6. Super Noob

    Super Noob AK Subscriber Subscriber

    Messages:
    326
    Location:
    Fort Myers, FL
    Tuner Board:

    Before:
    [​IMG]

    After:

    [​IMG]

    [​IMG]

    Have read so many folks don't recommend touching the FM board. I have never had a problem with a working FM board not responding well from a recap. The rule really pertains to replacement of the transistors. Changing these will require a realignment - not eltro caps.

    The Fisher tuner is really good (one of the best I have had).
     
    Last edited: Feb 1, 2019

     

    Please register to disable this ad.

  7. Super Noob

    Super Noob AK Subscriber Subscriber

    Messages:
    326
    Location:
    Fort Myers, FL
    Finishing Up...

    Here is the cap list I assembled = my hopes is that this might help someone who might elect to rebuild this set.

    https://drive.google.com/open?id=1A6FZ4NnxqyNGD_11rUcYS2kWawSJGfxI

    The Top View:
    [​IMG]


    This is an impressive unit - the toroidal transformer should give you a feeling for the quality as well I like the external heatsinks.


    Basically have addressed the weak spot of this unit = STK 0080 power packs. It should just be a matter of time until a non-working RS-2010 shows up. Depending on the price and condition - I would definite do it again. DC offset turned out acceptable at roughly 15mV per channel.

    It sounds great + strong = thanks to RCS16 and the others for making a replacement of the STK.

    [​IMG]
    [​IMG]
     
    kirkendoll and merlynski like this.
  8. rcs16

    rcs16 AK Subscriber Subscriber

    Messages:
    4,246
    Location:
    Baldwin, Ontario, Canada
    Well done, great pics, nice looking unit. Enjoy
     
    Super Noob likes this.
  9. fred soop

    fred soop Super Member

    Messages:
    2,102
    The Oliver criteria (followed by Cordell, Self, and others) is that the emitter resistors should be biased to approximately 24 mV regardless of the value of the resistors or the resulting bias current. This is well documented in Selfs power amplifier book and both Self and Cordell have graphs showing effects of improper bias. I don't think any of this was well known when most of our vintage equipment was designed. Leach does not mention it in his mid 1970s articles. It appears to have been first published by Barney Oliver in the February 1971 HP Journal.

    I also understand that running 10 kHz at 1 watt into a 4 Ω load (2 V RMS) and looking at a scope, the crossover distortion should be obvious. I have not had the chance to actually test this info.

    As for the tuner, most of the capacitors will be ceramic and can be left alone. The few electrolytics are mainly bypass and do not contribute to the alignment.
     
    Super Noob likes this.
  10. Super Noob

    Super Noob AK Subscriber Subscriber

    Messages:
    326
    Location:
    Fort Myers, FL
  11. Super Noob

    Super Noob AK Subscriber Subscriber

    Messages:
    326
    Location:
    Fort Myers, FL
    100 Caps / Relay / 4 Transistors / 4 Diodes / 2 Build STK (RCS16 Packs).

    This unit sounds very nice = SOLID. Cannot image a better STK conversion candidate than this monster.
     

     

    Please register to disable this ad.

Share This Page