THE FISHER model 700-T

Discussion in 'Fisher' started by quiet, May 2, 2018.

  1. quiet

    quiet AK Subscriber Subscriber

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    I pickup a couple of 65 to 75 receivers a month. Most out of curiosity. But none have been as hard to come by in relatively good condition and working well as this Fisher 700 and the Magnavox 1500 without an amount of money that made me think twice.
    When this one became available at $100 to the door I pushed the go button. I didn't think I could reasonably expect to do any better. I'm under the impression a true restored unit would be multiples more costly. What I'm after is a good representation of early Fisher SS. Not a full on mint museum piece.
    For a few days after placing the order I realized I was anxiously awaiting it's arrival. That hasn't happened before. And here it is. Well used with no apparent shipping damage. Surprise, it works good too.
    A cursory test shows the volume though the speakers to be detectably low on the left channel. Same result FM or inputs. It is correct on the headphones. Other than that I can't find a thing to complain about.
    I have a 65 Sansui TR-707-A, a 64 Harmon Kardon SR-900 and a 65 Kenwood TK-60. They all work and sound great with similar defects. They're gonna sit till I get this one sorted out. This is the one that has my attention now. I hope for good reason.
    Looks like I'm onto my first restoration.
     

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  2. fred soop

    fred soop Super Member

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    If the volume is balanced between channels using headphones but not speakers, that leaves very little that could be wrong. A problem would have to be between the headphone resistor take off point and the output terminal block. That leaves a few wires and the speaker selector switch. Can you input a tone from a generator and measure output at both the headphone jack and speaker terminals?

    Another possibility. Is the volume level set differently for speakers and headphones? If so, it could be a volume control tracking error at certain levels.
     
  3. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

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    The 700-T has the headphones powered direct off the output's, but the speakers have the speaker switch between the outputs and the speaker connections.
    DeOxit and Faderlube have a good chance of fixing that problem (unless you have a weak amp. but that would show up on headphones too).

    Note that the 700-T has 2 service manuals that we know of. Serial #'s starting at 10001 is one (on HifiEngine) and Serial #'s 30001 and up, the other on FISHERCONSOLES.com Use the one that your serial # falls into.

    One problem that this group of receivers (500-T,550-T,700-T) has is a bad PEC in the Tone Control board, more often than not on the left side. The part # is PC501B87-25. Most often the 10K resistor btwn pins 1 and 7 has gone high causing low volume on that side. Read ohms btwn pins1 and 7 then determine what value is needed to bring it back to 10K, strap it across 1 and 7. Test.

    1968 200-t_700-t specs.jpg
     
  4. quiet

    quiet AK Subscriber Subscriber

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    I just saw the responses, let me digest that for a few minuets.
     
  5. quiet

    quiet AK Subscriber Subscriber

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    The balance is correct on the phones but not the speakers. This is over the entire volume range. Don't have a tone generator. No indication of faulty or dirty volume control.
    The speaker switch has been mentioned as suspect. Lets move the speakers from A to B.
     
  6. quiet

    quiet AK Subscriber Subscriber

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    Went from A to B, same 70-30 inbalance. Lets swap the speakers left-right.
     
    Last edited: May 3, 2018

     

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  7. quiet

    quiet AK Subscriber Subscriber

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    Nope, it's not the speakers. All controls AND speaker switch are responsive and appear to be working properly.
    What's next? Clean speaker switch and look for anything obvious? If no success check 10 k resistor between pins #1 and #7?
    Thanks for you help.
     
  8. fred soop

    fred soop Super Member

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    Aha! Check R43 and R44, 0.15 Ω resistors between the speaker common terminal and ground. These are used for the speakers but not the headphone circuit. They are in series with the speaker return leads and also affect feedback.
     
  9. quiet

    quiet AK Subscriber Subscriber

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    Ok, I got the schematic off HiFi. The part that larryderouin id'ed as PC501B87-25 is I believe part PC50B-187-25. I have not successfully checked this part yet. There are two of these on what I think is the "audio control amplifier" board # 1278-2 . I got these #s from the actual receiver part and the schematic. I think this will help you id the unit that I have.
    I'm looking for parts R43 and R44.
     
  10. quiet

    quiet AK Subscriber Subscriber

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    I found them on the schematic. They're not identified by # but are associated with driver 1489-3? They go strait to ground from speaker return line? Located between the speaker and the feedback line?
    That's it for the night.
     
  11. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

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    Make sure your serial # falls into the range for the manual. There were minor changes in the later manual. Two manuals. 10001 and up and 30001 and up.

    The manual and the P.E.C. denote the number differently with the dashes. Same part. Your on the right trail. If R43 and R44 are OK, the P.E.C. (Packaged Electronic Circuit) is most likely suspect. when you're facing the front the LEFT side PEC is one next to treble control. The right is next to bass control.
     

     

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  12. quiet

    quiet AK Subscriber Subscriber

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    I just ordered both original factory manuals. $20.
     
  13. quiet

    quiet AK Subscriber Subscriber

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    I now have the factory manuals in hand. They are complete and in very good condition. We'll see how far I get before I post again.
     
  14. jdsalinger

    jdsalinger AK Subscriber Subscriber

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    WELL worth your effort. They are keepers. So clear & detailed, not to mention, beautiful.
     
  15. quiet

    quiet AK Subscriber Subscriber

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    That's what I'm hoping. Not expecting the end all miracle receiver. Just a good solid Fisher from that generation.
     
  16. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

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    The 700-T is as good as they come from that period. It was FISHER's Top receiver from 1967 to 1969. It was replaced by the 500-TX/800-T
     

     

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  17. quiet

    quiet AK Subscriber Subscriber

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    I'll get this little channel imbalance fixed first. Then I'll go for all the usual old suspect parts.
    I usually replace rather than repair a failed receiver if I liked it. Not so easy with Fishers. So this one will get special attention.
    It does sound surprisingly good just the way it is. But that imbalance makes my 30 watt Fisher a 15 watt Fisher.
    And we can't have it competing at a disadvantage to the 30 other old receivers here. That just wouldn't be fair.
     

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