Fisher TFM-1000 FM Stereo Tuner

Discussion in 'Fisher' started by jonboy55, Aug 22, 2017.

  1. radioactive

    radioactive tube gear fanatic Subscriber

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    Iirc a ak member Brian said that these tuners were problematic even when new and working on them was a even a pain in the ass when they came out. Ff 50 years and the problems can be even worse.
     
  2. fred soop

    fred soop Super Member

    Messages:
    1,761
    I think all the transistors are socketed. If so, corrosion on the leads after 50 years will be a problem. You might try pulling each transistor and carefully sanding the leads with 400 or 600 grit until they are shiny. A longer term solution would be to remove the sockets and solder the transistors. The early solid state equipment was built similar to tube units with socketed transistors but they usually don't go bad unless abused.

    Can you connect directly to the output of the detector and send that signal to an external amplifier? That would be pins 9K (hot) and 9L (ground) from the limiter detector board. Yes, it will be mono, but this will eliminate the multiplex decoder and all of the audio circuits in the tuner. The front end and IF have no electrolytic capacitors and the limiter detector board has 3 10µF. The ceramic capacitors are unlikely to be bad.

    As for voltage ratings on replacement capacitors, we can determine reasonable values once it is determined which capacitors need replacing.
     
  3. jonboy55

    jonboy55 Well-Known Member

    Messages:
    613
    Location:
    Long Island, New York
    I've been working on the TFM-1000 and replaced about 5 electrolytics that were visual leaking. Cleaned the controls once again. Now the tuner sounds much better but the output volume is a little low. Also, the biggest problem is that after about 10 minutes of playing, one of the channels slowly fades out. Voltage checks are within tolerance even after the one channel stops working. I sure there is some part(s) that when heated up fails - which is causing the one channel to stop working.

    I feel transistors are either good or bad so it's probably a cap or a resistor. But as previously suggested I will clean the transistor leads and sockets just in case.

    Any additional suggestions would be gratefully received.

    Thank you.
     
  4. larryderouin

    larryderouin Do I get Food, Med's, or more gear this Month? Subscriber

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    Jon;

    Looks like the preamp output is split from the SE8001. One side goes to the OUTPUT LEVEL CONTROL(OLC) and the other goes to the lower pair of SE4010's and thru a transformer, which give you 600ohms, and a separate winding for the headphones @ 4 to 16ohms.

    Back to the OLC, the lead splits again one side going to the OLC, and the other side directly to the TAPE OUT. Try the TAPE OUT if the OLC @ max (full clockwise) isn't cutting it. If you get more gain then either the OLC is still dirty, OLC is damaged or broken, OR the resistor banks to the OLC are out of whack.

    The Plastic MALLORY caps (with the value/voltage on top) I've had a rash of bad ones. Especially the 4.7uf and lower. FISHER loved these things, but by now they are mostly all leakers (electrically). The 1uf are mostly 70 or 80v and I replace them with 1uf 100v Panasonic ECQ films. Above 2uf the films get really large and unless it's out in the open I'll switch back to lytics.


    NTE shows SE4001 crossing to NTE123AP
    "........".........SE8001 crossing to NTE128

    One of my many S.S. Service manuals has a Fairchild x-ref for the SE4010 but the SE8001 is a new one for me. I'll look it up and get back to you with the #.
     
    Last edited: Aug 28, 2017
  5. jonboy55

    jonboy55 Well-Known Member

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    Location:
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    Hi Larry -

    Thanks for the advice and help.

    I'll let you know how it goes.

    Jon
     
  6. audmod01

    audmod01 AK Subscriber Subscriber

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    Location:
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    After this many years most all the electrolytics are gone bad. The symptom you describe sounds very much like a capacitor that opens up after on a while, especially since the voltages appear to be correct. Capacitors are famous for such problems. The sockets of the transistors may have been gold plated, but the leads of the transistors usually were not. Dissimilar metals in close contact are not a good idea and can cause electrolysis to take place especially when combined with humidity and air pollution. Sometimes removal and reinsertion of transistors may restore enough corrosion free contact that a circuit will operate again for some period of time.

    It does seem odd that Fisher produced the service manual without a parts list. I wonder if they eventually may have released a parts list as an addendum to the service manual.
    Joe
     
  7. larryderouin

    larryderouin Do I get Food, Med's, or more gear this Month? Subscriber

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    Joe; More often than not the early S.S. manuals from 66-67 to 1970 do not have parts lists . Usually I take and find the part and note the value/voltage on it and note it on the schematic for that board. It's a PITA, but occasionally a parts list does turn up for a unit. These were mainly from auth. repair shops that went defunct.
     
  8. audmod01

    audmod01 AK Subscriber Subscriber

    Messages:
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    Location:
    Tioga, TX
    Larry;
    Yes that is basically what I was referring to. Warranty service stations often received direct bulletins and service notes from Fisher Radio Corp. I saw that on the MF-300 tuner series while I worked for a warranty service station. It would be nice if anyone who worked for such a concern would scan and provide such information to the AudioKarma.org database. It is a time consuming chore to look at each capacitor in a set and document it when possible service information regarding such items may exist. However, I expect that our group of Fisher followers may be so small that the plea for such information will not be noticed. If I owned such an item I would undertake documenting the parts.
    Joe
     
  9. jonboy55

    jonboy55 Well-Known Member

    Messages:
    613
    Location:
    Long Island, New York
    I'm still working on it. Replaced more electrolytics but the problem persists. One channel keeps fading out after approximately 10 minutes. Hopefully it's not a resistor that is heating up and causing the problem.

    I do voltage measurements when the problem occurs and there are no voltage changes when the channel fades out.

    Very frustrating.

    Does anyone think that spraying the transistor sockets to clean them would be of any help?

    I'm going to leave it alone for a few days and work on something else.
     
  10. larryderouin

    larryderouin Do I get Food, Med's, or more gear this Month? Subscriber

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    Spray some DeOxit into a cap. Then dip the transistor legs into the DeOxit. Insert the transistor into the socket and pull it out again. Then repeat this a few times. Finally give the socket a short blast to flush out what contaminents remain. The transistor legs should have cleaned up from the friction also. If not wipe them on a clean kitchen green nylon scrubbie with some DeOxit sprayed onto it. Then re-insert them into the sockets.

    I looked for those transistor x-ref on my 2 desktops. Not there. Probably on my old dell laptop that has some serious power problems. I'll see if I can get it running long enough to dump all the manuals to a flash card and transfer them.

    Do you have any canned air??? If so turn the can upside down and when the problem starts, give each of the transistors a very quick shot of the spray. It'll cool down the transistor and hopefully it'll come back up enough to show it's a heating failure for that part. Don't use a lot, and frost the part. just enough to cool it down.
     
    Last edited: Sep 4, 2017
  11. jonboy55

    jonboy55 Well-Known Member

    Messages:
    613
    Location:
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    Thanks for the advice.

    I'll work on it later this week.

    Have some deadlines at work.
     

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