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New to me Fisher KX-200 amp re-capping

Discussion in 'Fisher' started by lopezluna, Oct 8, 2018.

  1. lopezluna

    lopezluna AK Subscriber Subscriber

    Messages:
    53
    Location:
    San Diego, California U.S.A
    Hi fellas, I just picked up a Fisher kx-200 amp in working order and it appears to be all original. All tubes are fisher labeled except for the 7591 output tubes (Raytheon). So far I have cleaned the knobs, faceplate, chassis, and deoxit the switches and pots. From reading all your posts I know a re-cap job is needed as a safety/maintenance for reliability and am looking into getting a rebuild kit. I contacted Jim about getting a cap kit from him as many fellow AK'ers have mentioned him in other posts but in his kit he uses other caps in place with clamps to secure them instead of the original looking replacement multi cap cans that look stock. I would like to replace the old cans with new cans for two reasons, one is to keep the stock look and second is because I am not very knowledgeable in electronics and feel this would be easier for me to just remove and replace. Anyone used the cans from Hayseed yet? Any advice on wich route I should go with as far as the multy can cap replacement? I want to make this amp as good sounding as I can. Im sure most of you know more about this that I do. Here's some pix of my amp. Thanks everyone In advance for advice or suggestions, Ben IMG_2981.jpg IMG_2985.jpg IMG_2978.jpg IMG_2979.jpg IMG_2980.jpg
     
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  2. bhamham

    bhamham AK Subscriber Subscriber

    Messages:
    1,991
    Location:
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    The KX-200 is a great amp! I listen to my restored one daily. Nice job cleaning yours!

    Hayseed's can caps are pretty popular with Fisher restorations. I personally like to stuff my own. I think the look is more authentic than Hayseed's shiny new cans. Plus, if you use an oscillating saw to cut them at the base where you leave the base intact there's no desoldering the big solder blobs to remove the old cans; and you don't need to undo all the wires to the can terminals. Just another way of doing it.

    http://www.audiokarma.org/forums/in...eplacing-fisher-can-caps.644152/#post-8563272
     
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  3. lopezluna

    lopezluna AK Subscriber Subscriber

    Messages:
    53
    Location:
    San Diego, California U.S.A
    Thanks for the info bhamham and for the complement on the cleaning. I just feel theres less room for error If I went with replacement cans. Im going to look into oscillating saws.
     
    Last edited: Oct 8, 2018
  4. bhamham

    bhamham AK Subscriber Subscriber

    Messages:
    1,991
    Location:
    Austin
    Definitely! Stuffing cans yourself can lead to errors. Lots of folks here use Hayseed cans, I've not read one bad word about them.
     
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  5. lopezluna

    lopezluna AK Subscriber Subscriber

    Messages:
    53
    Location:
    San Diego, California U.S.A
    Im thinking replacing all the big cap cans is the route im going to take unless someone on this site tells me there's a benefit in re-stuffing besides the difference in cost. I can solder and have replaced multi cap cans on other amps before.Im just not to good with schematics and want to make this re-cap as easy as I can for myself. Thanks for your input bhamham, all is appreciated. Ben
     
  6. lopezluna

    lopezluna AK Subscriber Subscriber

    Messages:
    53
    Location:
    San Diego, California U.S.A
    Im going to measure voltages on plates and screens pins 3 and 4 of output tubes and pins 4 and 5 of heater tubes in DC volts as soon as I get home today. Can anyone tell me if the correct way to measure would be groung lead on ground and pos lead on pin 3 then pin 4 Or do I measure ground lead pin 3 and positive lead pin 4? The amp is working I just want to make sure Im getting proper voltages. Thanks
     

     

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  7. notdigital

    notdigital AK Subscriber Subscriber

    Messages:
    2,237
    Location:
    NYNY
    I'm a dedicated can stuffer!! In doing so I usually cut the can at the flange leaving all the underside components untouched. Unlike Bruce, I use a hack saw blade. I find that I can control it more than a oscillating saw.

    As far as mistakes, well yes. But once you develop a methodology, it's all pretty straightforward. If you look at the can itself, the sections should be marked with symbols relating to the respective caps housed in the can. If you look at the underside of the can, the wafer will be similarly marked with symbols. Finally, if you look at the schematic, each section of the can has a value. All you have to do is make sure the individual caps match the marked terminal underneath per the can/schematic. Assembling the caps is a trick as it has to fit the can so you have to be mindful of cap dimensions.

    F or reference, I've attached some pictures showing a can I stuffed in my CX-2. Of course, technique varies from person to person but doing some research will likely reveal enuf for you to develop a preference.

    Good luck!!
     

    Attached Files:

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  8. lopezluna

    lopezluna AK Subscriber Subscriber

    Messages:
    53
    Location:
    San Diego, California U.S.A
    Thanks for the pictorial notdigital and info. Is that a ground wire going thru center of base of can and If im correct it appears all negatives from caps are soldered to it at one location and all positives from caps go to their assigned connector wich was part of the old can base, then you ground the end of wire to ground where can was originally connected
     
  9. lopezluna

    lopezluna AK Subscriber Subscriber

    Messages:
    53
    Location:
    San Diego, California U.S.A
    Update. I started checking voltages this afternoon and all seemed ok until I got to testing cathode voltage on V10. The reading was 0.17 so I quickly powered my amp off. I powered amp thru variac at 117v. Plate voltages for V7 =439v V8=439v V9=439v V10=440v. Next I went to cathode voltages and V7=0.51 V8=0.62 V9=0.60 (V10=0.17 WOW) Ok I swapped tubes from V10 to V9 and the low voltage followed the tube so tube is causing it and must be a weaker tube. I read pin#5 can help find out if tube is strong or getting weaker. Now the rest of the voltage readings V7=-15.8 V8=-16.8 V9=-16.9 V10=-15.4 How do the voltages seem to you guys? Anything that I should be worried about besides the one tube?
     
    Last edited: Oct 8, 2018
  10. notdigital

    notdigital AK Subscriber Subscriber

    Messages:
    2,237
    Location:
    NYNY
    Yup, you got it!

    In this example, I built the cap assembly first and then mounted it onto the can cap base. In other instances, I've mounted the replacement cap one at at time, binding them together after they have all been mounted. It all depends on the number of caps, their sizes, and whether/how they finally fit in the can. Once I'm sure everything fits, I flip the unit over and solder the connections.
     
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  11. lopezluna

    lopezluna AK Subscriber Subscriber

    Messages:
    53
    Location:
    San Diego, California U.S.A
    Great info notdigital, I appreciate it. Thanks for the pictorials and great info. I just might stuff the can on my fisher tuner when I get to working on it.
     

     

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  12. bhamham

    bhamham AK Subscriber Subscriber

    Messages:
    1,991
    Location:
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    Have you changed out the meter resistor from 390 ohms to 240? That will certainly help with quiescent current for the output stages as Dave G recommends in the other KX-200 thread.

    I've gone through a number of these old Fisher amps and receivers and it's very rare that you find one with all outputs good; usually, it's three good and one very bad.
     
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  13. lopezluna

    lopezluna AK Subscriber Subscriber

    Messages:
    53
    Location:
    San Diego, California U.S.A
    bhamham at this point the amp is all stock still as far as I know. As far as the 240ohm resistor for the meter it is on order. I will definitely install it as soon as it arrives. I was measuring voltages to see where it is at before I start replacing all the caps. Thank you very much for the info as I am new to this and appreciate any and all advice. Im thinking about buying a quad of Electro H tubes to see if everything tests ok. Thanks again. Ben
     
  14. bhamham

    bhamham AK Subscriber Subscriber

    Messages:
    1,991
    Location:
    Austin
    Good plan, Ben. Looks like your on the right path. Change out those cans and all the other electrolytics. New outputs, too.

    Lots of guys here who have been where you are to help. Soon you'll have a fantastic playing integrated amp, one of Fisher's best. All the best with it, Bruce
     
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  15. lopezluna

    lopezluna AK Subscriber Subscriber

    Messages:
    53
    Location:
    San Diego, California U.S.A
    Thanks bhamham. I cant wait to get this restored. I have a console that I am restaining with a fisher ta-600 that I just had a shop rehab for me that the wife keeps pressuring me to finish. Thanks again bhamham
     
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