Fisher 400 owners PLEASE READ....IMPORTANT!!!!

Discussion in 'Fisher' started by larryderouin, Oct 1, 2015.

  1. Ricky W

    Ricky W New Member

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    More pics
    I more pic
    Please forgive me. New to forum and learning the mechanics of it. and doing this on my phone. Let me know if i missed anything in pics.
     

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  2. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

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    Thanks Rick. That certainly narrows it down to a FACTORY VIRGIN. The 926 4388 number on the transformer is theEIA CODE. 926 is the manufacturer TODD ELECTRIC, Yonkers, N.Y. 4388 is 38th week of 1964. So it's quite possible your dad bought it in Dec. 64 to Mar 65. I would think later as it had to be truck shipped to S.D.

    Dave; What if the AX transformers on the 30001to 47999 are an interim build before the 4 IF strip chassis came out, but it has all the other bit's and pieces? Or the high numbered units with the non AX trannies are thrown together to get stock out while they were waiting on some more AX Transformers? Possible huh?

    With Ricky's low numbered AX unit, and ART's and friends high numbered non AX units, The NFB circuit should match that particular transformer, correct? or is it a broad enough parameter that it would hold up with the wrong parts in it?

    Just throwing out some questions that hit me while watching Point Blank.
     
  3. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

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    Don't sweat it. We're ALL learning this "CAN OF WORMS".
     
  4. arts

    arts Super Member

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    Rick- my can of worms comment was not directed at you or you efforts,which are much appreciated. It was a reference to a comment I made much earlier in the thread,when I initially ''opened'' the can of worms with information that didn't follow the existing information,thereby raising even MORE questions for Larry to try and make sense of.
     
  5. dcgillespie

    dcgillespie Fisher SA-100 Clone Subscriber

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    At this point, who knows if any of our theories hold any water anymore. But it would seem to me that eyeballing the NFB resistor would be the easiest way to tell the impedance of the actual OPT installed. Since the impedance shift between the transformers is significant, I would think that Fisher would make the change between the required NFB resistors mandatory with any transformer change, as otherwise, there would be a quite obvious performance change (if only in displayed gain) at normal listening levels. By making the appropriate NFB resistor follow the appropriate OPT, the apparent performance changes would be minimized at normal volume levels, so that the actual performance difference produced between the two transformers would only be apparent at much higher levels.

    Dave
     
  6. arts

    arts Super Member

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    It would seem that we can no longer trust the transformer # to be an accurate indicator of the units impedance. Short of measuring each transformer individually,the NFB resistor would seem,at first glance,to be the next best bet,although at this point I wonder if we can trust this information either. After all,deciding on a 10K+ plate-to-plate impedance was taking quite a liberty to start with. I wonder if they felt the same way about the NFB?

    Also,I'm still attempting to contact other 400 owners I know to obtain more info.

    Art
     
    Last edited: Nov 22, 2015

     

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  7. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

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    Rick; The "CAN OF WORMs" I was referring to is this forum format. It's about 6 weeks old and some are still trying to come to grips with it after many years of the old format.
     
  8. Ricky W

    Ricky W New Member

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    [QUproblemE="larryderouin, post: 9216825, member: 42316"]Rick; The "CAN OF WORMs" I was referring to is this forum format. It's about 6 weeks old and some are still trying to come to grips with it after many years of the old format.[/QUOTE]
    No problem. Let me know if you need anything else from me. Obviously I need to have some work done on the Fisher to prevent unwanted damage if im going to use it regularly. I used to work it pretty hard when I was a teenager until I bought my Sherwood in high school. It hasn't seen much action since the mid 70's. Thanks, Rick
     
  9. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

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    I think the thing to do would be to check and verify the correct values. If incorrect, then replace with correct values.

    1.) IF you have the AX transformers on a unit BELOW 48001 verify that the NFB component values match those in the 48001 manual for the AX transformer 10K plate to plate impedance. (*)

    2.) If you have the non AX transformers in a unit above 48001, verify the NFB component values as outlined in the 20001-29999 manual for the non suffix'ed transformer 6.4K plate to plate impedance(**)

    (**) NON AX transformer NFB VALUES. C60 & C61= 330pF R90 &R91 = 3.9KoHms

    (*) AX SUFFIX transformer NFB VALUES. C91 & C92 = 560pF R113 & R114 = 2.7koHm
     
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  10. arts

    arts Super Member

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    More information,provided by Howard at the fabulous Hotel2tango recording studio. He sometimes uses this machine for playback listening. Thanks Howard! Go Fisher!

    SN: 64023W
    OPT: T-1020-116-0 AX, 352609
    IF: 4-tube
     
  11. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

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    Thank you, Arts and thank Howard for me/us.

    As of TODAY the counts are. The anomalies are counted in the Early/Late totals.

    EARLY versions 7 Most of these are in the 20000 series with 1 or 2 in the low 30's.
    Early with AX xfrmr 1

    LATE version 19 The majority of the anomalies in this group are above 60,000 serial.
    Late with Early Xfrmr 4.

    TOTALS 26 units with 5 of these being anomalies. 14.28% Early anomalies. 21% Late anomalies.

    From what we've got so far there is about a 90% certainty of the 48001 serial being the cut off point from Early to Late versions with a few anomalies, which can have the NFB verified correct for the impedance of the output transformer as set forth in POST # 89. The values will depend on the Transformer SUFFIX and impedance value. If the R/C network is wrong for the Xfrmr, the R/C can be changed easily.

    So, Lets Recap.

    NORMAL PRODUCTION 400's

    A.) EARLY VERSION: Serial # 10001-47999. Output Transformer T-1020-116-1(or 2) RF/IF Tubes Qty Five (5) V1 thru V5
    Note: V4 is a 6HS6

    B.) LATE VERSION: Serial # 48001- end of production, Output XFrmr T-1020-116-1AX or 2AX, RF/IF Tubes QTY SIX (6) V1 thru V6 Note: V4 is a 6AU6

    The above are the Normal and Customary types as designed and built by FISHER, which at least 95% (conservatively) are of these two types.(The total percentages above are high due to low counts, higher response would show a more accurate percentage of anomalies). Checking the values to verify correctness is fairly simple.

    Then you have the two major anomalies, which are basically:
    C.) the AX transformer on the Early version 400 hopefully with the attendant changes to the NFB Network.
    D. the (A or No suffix) transformer on the Late version 400, hopefully with the attendant changes to the NFB Network.

    These can be checked easily to verify the Transformer impedance to the type (A or AX), and the NFB R/C network to the Transformer. If the values match, make the appropriate notations(Transformer part #, Resistor and cap values) in the manuals for your unit. If the values do not match between the R/C network and the transformers, the R/C network can be changed. This is easier and very much cheaper than replacing the transformers with the correct ones.
     

     

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  12. Catmanboo

    Catmanboo AK Subscriber Subscriber

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    Larry, just stumbled upon this thread this a.m. here I go off the rails again, had to dig out my 400. (Literally ). S/n 33555-s, opt no's:t1020-116-1 & 2. Number under that:9264232. No numbers on pwr.trans, but looks like something else was mounted in those holes once upon a long time ago.
    Rf tubes v1-6ha5, v2-6ab4 ( now that's an oddball!), v3&5-6au6, v4-6hs6. fwiw.
    For some reason, I can't upload pics any more, it says file too large. Calling bullshiite on that, technical snafu ... Jerry de k8cat
     
  13. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

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    Catmanboo. Your output's were made by TODD ELECTRIC (NYC) 42nd week of 1964 which would make it a 1965 model.

    If your camera is set to any larger than 1024x768 it usually won't take them. Try dropping the size to below 1024x768 and 1.7meg size constraint.
     
  14. Catmanboo

    Catmanboo AK Subscriber Subscriber

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    A-ha! I figured it would be something simple but surmountable. I'll fool with it tomorrow. As for my 400, I've had it since the '80's. If I recall, I parked it due to tuner issues, but I could be wrong. How tempting it was to variac it up today, but it's been dormant too long. Gonna fab a dbt tomorrow, use that with the variac & see what happens.
     
  15. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

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    Sounds like a plan. Use a 150w bulb (My DBT has a 3way socket so I can vary the wattage on the fly). Home Depot has them (the 150w) right around the 3ways.
     
  16. Catmanboo

    Catmanboo AK Subscriber Subscriber

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    I hit my electrical parts stash first thing this a.m., just finished a combo variac/dbt. I can do both simultaneously . 150w bulb has dim glow with the 500c on it, now ready for anything. I like your 3-way switch idea though, future project, maybe. In the meantime. I've bulbs from 7 watt to 300, working with what I have.
     

     

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  17. hairy carbin

    hairy carbin New Member

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    84702C17-9394-4141-9202-9FE5F7E27772.jpeg Hi, new to me Fisher 400 serial number 17716F, hope this helps.
    Need to go thru, getting a kit I guess, cheers!
    P.S. no papers no history, found in a storage unit.
    I haven’t plugged it in as per advice read here.
     
    Last edited: Jul 11, 2018

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