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Kenwood KA-1000 recap?

Discussion in 'Kenwood-Trio/Kensonic-Accuphase' started by Cosmin2000, Apr 18, 2013.

  1. Cosmin2000

    Cosmin2000 Active Member

    Messages:
    141
    Location:
    China/Romania
    Hello, AK members!
    I recently bought a very rare, sought for, Kenwood KA-1000 stereo amplifier.:banana:
    First, I must say that I'm very impressed with the sound of this vintage beast, it's one of the best sounding integrated I've listened so far. The amplifier is European version on 220V and functions well in it's factory version. So, one question arise: it is possible to upgrade this amp by replacing the 33 years old vintage electrolytic capacitors? Will this be worth it? Or I just have to leave it like it is, factory built? Any experiences with the recapping process of this amp? Thanks in advance?
    Pictures here:
    https://plus.google.com/photos/116706320971586318484/albums/5868155179918733729?banner=pwa
     
  2. dr*audio

    dr*audio Fish fingers and custard! Subscriber

    Messages:
    17,964
    Location:
    Cleveland, Ohio
    This is a very nice amp. I uses a Sigma Drive output stage, licenced from Nelson Pass. I have worked on this model several times. EVery couple of years I have to replace some driver transistors because they run them hot. Also the factory soldering is horrible, lots of bad solder joints. So go through it and replace the caps if you want, touch up all the bad solder joints, and I would replace all the pre driver transistors in the tall TO-92 cases, those are the ones that go bad. Also look for bad solder joints in the regulated power supply.
     
  3. Cosmin2000

    Cosmin2000 Active Member

    Messages:
    141
    Location:
    China/Romania
    Thanks, dr*audio! I've noticed that the amp is getting really hot, especially on the pre-driver part of the top cover. The question is: by replacing the transistors will the sound alter from the original which, I must say, suits my tastes. As for the new capacitors, I've selected the new developed 105°C Nichicon KA:
    http://www.hificollective.co.uk/components/nichicon_ka.html
    Has anyone experienced with the sound of these?
    I've worked in the past with Nichicon KZ Muse, FG and as bipolar signal caps Mundorf ECap.
     
  4. dr*audio

    dr*audio Fish fingers and custard! Subscriber

    Messages:
    17,964
    Location:
    Cleveland, Ohio
    Replacing the transistors will not change the sound, but if you don't replace them, sooner or later the sound will stop.
     
  5. Cosmin2000

    Cosmin2000 Active Member

    Messages:
    141
    Location:
    China/Romania
    IMG_0315.JPG Condensatori de schimbat KA-1000.JPG IMG_0320.JPG IMG_0321.JPG IMG_0339.JPG

    Reviving an old topic. Because I enjoy so much the sound of the Kenwood KA-1000, and because it has 36-37 years, I intend to make a full recap this summer.
    Also, because in Romania the mains voltage was raised from nominal 220V to 230 V+-10% I am a little worried about the main 10000 microF/63V ELNA CEW filter caps which, according to the schematics, have just 1V DC difference from the real voltage applied to them, e.g. 62V CC. Therefore, some 71V or 80V replacement main filter caps are mandatory.
    So far, I have bought the electrolytic replacement caps and even some new film caps which I intend to install after the electrolytics.
    A few information about this amplifier:
    - it has two different enclosures: KA-1000PS, and KA-1000 amp linked by a multi-pin socket which feds the AC voltages from KA-1000PS to KA-1000;
    - KA-1000PS has three transformers, two big ones for each channel and a smaller one for power on control;
    - KA-1000 has the Sigma Drive circuit which uses four wires to connect to each speaker only for Speaker A;
    - the KA-1000 has a dual-mono configuration, with separate power supplies for preamp (regulated +-60V from +-73V) and each main amp channel (+-62V);
    - filtering for each power amp channel is made with two ELNA CEW 10000 microF/63V (C73, C74,C75,C76);
    - filtering for preamp is done with C69,70 (470 microF/100V) in parallel with C67,68 (330 microF/100V)
    Here is a picture with the amp and some inside pictures with the actual caps in the Kenwood KA-1000.
    All the electrolytics are ELNA RE series, while a few other caps found in phono board are marked TRIO (interesting, no?).
     
    Last edited: May 16, 2017
    Ds2000 likes this.
  6. Cosmin2000

    Cosmin2000 Active Member

    Messages:
    141
    Location:
    China/Romania
    I think this is the first Kenwood KA-1000 recap here on AK (I never saw another attempt on this forum).
    Here is the plan:
    1. Preamp power supply capacitors (which are mounted on the amp board X09-1610-10, see picture 1):
    # C69,70 470 microF /100V will be replaced with ELNA RJH 105 deg 680 microF /100V ( measured with a UNI-T 890D multimeter they have 708 microF and 714.6 microF)

    # C67,68 330 microF/100V will be replaced with ELNA RJH 105 grade 680 microF /100V (measured capacity of 698.3 microF and 702.5 microF) or should I keep the original capacity by installing two Nichicon PM 105 deg 330 micro/100V (measured 345.1 microF and 347.7 microF)?

    # C65 33 microF/100V will be replaced with Panasonic GE 105 grade 33 microF/100V (measured 33.2 microF!)
    Obs. : C69,70 C67,68 will receive each a small shunt film capacitor WIMA MKS2 1.5 microF/100V.

    2. Capacitors from the phono preamp board, the one found in the side of the amp (see picture 2!):
    # C11,12 100 microF/10V
    ELNA Silmic II 100 microF/16V (measured 94.5 and 93.88 microF)

    # C17, 18,19,20 100 microF/35V
    ELNA Silmic II RFS 100 microF/63V (measured 98.8,100.4,100.8, and 100.5 microF)

    # C13,14 470 microF/10V
    PANASONIC 470 microF/25V 125 deg (measured 460.7 and 467.1 microF)

    # C 15,16 10 microF/35V BP - Signal capacitors!
    FOCAL MKP 6.8 microF/250 V J + Shizuki MKP 2.2 microF/100V K (measured 6.8 and 6.68 microF for MKP Focal, and 2.22 și 2.21 microF for Shizuki MKP)

    # C 29,30 470 microF/63V
    ELNA RJH 105 grade 680 microF/100V (measured 689.9 and 688.1 microF!)
    Obs: With the exception of C11,12 every cap from this board will receive a small NCC 0.33 micro/63V shunt film poliester capacitor

    3. Capacitors from FADER board circuit (see picture 3!)
    # C19,20 22 microF/16V
    ELNA Tonerex II 22
    microF/50V (21.6 and 21.7 microF)

    # C21,22 100 microF/16V LL
    Panasonic 125 deg. 100 microF/16V(measured 99.2 and 99.5 microF)

    # C23,25 10 microF/16V LL
    ELNA Silmic 10 microF/35V (measured 9.7 and 9.8 microF)

    # C24 470 microF/6.3V
    Panasonic FC 105 deg 470 microF/25V (measured 506.5 microF)

    # C130 47 microF/50V
    Nichicon KL 47 microF/63V (measured 46.4 microF)

    4. Capacitors from TONE CONTROL circuit (see picture 4!)
    # C13,14 0.22 microF/50V - These are electrolytic capacitors!
    NCC poliester film 0.22
    microF/63V (0.221 și 0.222 microF)

    # C31,32 2.2 microF/50V
    ELNA Silmic II 4.7 microF/50V (measured 4.62 and 4.65 microF) - I am wondering if is ok with the increased capacity from 2.2 to 4.7 microF???

    # C33,34 22 microF/16V
    ELNA TONEREX II 22 microF/50V(measured 21.3 and 21.4 microF)

    5. All other electrolytic capacitors found on amp board X09-1610-10 - picture 1!
    # C11 100 microF/10V
    PANASONIC 125 deg. 100 microF/16V (measured 92.88 microF)

    # C 29,30,59,60 2.2 microF/50V BP
    Nichicon BP-P
    2.2 microF/50V (measured 2.2 microF)

    # C61 220 microF/6.3V
    ELNA Cerafine 220 microF/25V (measured 218.8 microF)

    # C63 100 microF/25V
    ELNA TONEREX 100 microF/50V (measured 96.5 microF)

    # C109,110 47 microF/10V
    ELNA Silmic II 47 microF/50V (measured 46.2 and 47.5 microF)

    # C128 10 microF/50V
    Nipon Chemicon
    10 microF/71V (measured 9.3 microF)

    # C133 100 microF/6.3V
    PANASONIC 125 deg. 100 microF/16V (measured 93.88 microF)

    # C83,84,85,86 2.2 microF/63V
    NCC axial
    2.2 microF/75V (measured 2.2 microF)
     

    Attached Files:

  7. Cosmin2000

    Cosmin2000 Active Member

    Messages:
    141
    Location:
    China/Romania
    Pictures with the new capacitors.
     

    Attached Files:

    Last edited: May 14, 2017
  8. paul_ral

    paul_ral Active Member

    Messages:
    121
    Good job! De unde ai luat condensatorii?
     
    Cosmin2000 likes this.
  9. Cosmin2000

    Cosmin2000 Active Member

    Messages:
    141
    Location:
    China/Romania
    Some film caps are on my replacement list also. These will be replaced mainly with NISSEI film caps, while only two of 1500pF, found in the back of the main amplifier board will be replaced with silver-mica from Cornell Dubilier.

    # C55, 56 0.047 microF 5%
    NISSEI 0.047microF/100V

    # C91,92 0.01 microF 5%

    NISSEI 0.01uF/100V

    # C111,112 0.033 microF 10%
    NISSEI 0.033uF/100V 2%

    #C119,120,121,122,123,124,125,126 0.022 microF 5%
    NISSEI 0.022uF/100V 5%

    # Back board caps (see picture 3!):
    CORNNEL DUBILIER 1500pF/500V
     

    Attached Files:

  10. scimitar12

    scimitar12 Active Member

    Messages:
    233
    Location:
    Sterling, VA
    I used to own a KA-900. The sound was superb but boy, did it run hot.
     
  11. Cosmin2000

    Cosmin2000 Active Member

    Messages:
    141
    Location:
    China/Romania
    Yes, scimitar12, this series from Kenwood-Trio is notorious for runing very hot, but it sounds very special when the speakers are connected to the Sigma Drive circuit. My KA-1000 runs always with the top cover removed for two reasons: better air flow and, most important, to look at the innards from time to time....:D
    5142628_orig.jpg Sigma Drive.jpeg
     
  12. Cosmin2000

    Cosmin2000 Active Member

    Messages:
    141
    Location:
    China/Romania
    POWER SUPPLY Capacitors

    Kenwood KA-1000 has dual mono configuration, each channel having a transformer and two 10000 microF/63V ELNA CEW capacitors. The new filtering caps will be a combination of NICHICON KS 8200/71V paralelled by a Cornel Dubilier 380LX 1500 microF/80V. On top of these I will mount a SHIZUKI 2.2 microF/250V ±10% MKP.

    All in all, I will be very close to the original 10000 microF capacity. The capacity of the Nichicons is 7.8-7.9 mF, very close to the one specified by the manufacturer.

    The capacity of each blue CD 380LX is 1.4 mF. Also, good figures, close to the rated capacity denoted on these caps and within the tolerance range of ±20%.
     

    Attached Files:

    Last edited: May 31, 2017
  13. Cosmin2000

    Cosmin2000 Active Member

    Messages:
    141
    Location:
    China/Romania
    IMG_20170606_225710.jpg
    IMG_20170607_002922.jpg
    IMG_20170606_225427.jpg

    I have started the recaping process with the preamp power supply caps. The capacity was raised from 470 microF/100V to a 680 microF/100V 105°.

    Moreover, some Elna Silmics and Tonerex II have been installed in the tone control circuits. I found two 2.2 microF caps with a capacity of 3.4 and 3.6 microF, definitely out of capacitance range!

    Each of the preamp power supply caps was decupled by a Wima MKS2 1.5 microF/100V.
     
    Last edited: Jun 9, 2017
  14. Cosmin2000

    Cosmin2000 Active Member

    Messages:
    141
    Location:
    China/Romania
    IMG_20170607_002847.jpg
    IMG_20170608_012336.jpg
    IMG_20170608_012411.jpg
    IMG_20170608_012103.jpg

    Next, another pair of preamp power supply caps, located in the center of the amplifier board, 330 microF/100V were changed also with 680 microF/100V Elna RJH 105°. Also, they were each paralleled by a Wima MKS2 1.5 microF/100V film caps. Two1500pF caps located on the back of the amp board were replaced by Cornell Dubilier silver mica 1500pF/500V.
     
    Last edited: Jun 13, 2017
  15. Cosmin2000

    Cosmin2000 Active Member

    Messages:
    141
    Location:
    China/Romania
    More pics... the relay circuit capacitors were replaced with Nichicon BP-P bipolars, main power supply replaced with Nichicons KS 8200 microF/71V, shunted by film Shizuki 2.2 microF/250V.

    IMG_20170610_014912.jpg
    IMG_20170619_185709.jpg
    IMG_20170618_191534.jpg
    IMG_20170620_151547.jpg
    IMG_20170618_170842.jpg
     
    Last edited: Jul 19, 2017 at 3:37 AM

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