Basic recap and restore BOM parts list on Kenwood KA-4002 integrated amp

Discussion in 'Kenwood-Trio/Kensonic-Accuphase' started by dlucy, Apr 24, 2017.

  1. dlucy

    dlucy dlucy67 (Doug) Subscriber

    Messages:
    2,112
    Location:
    Philadelphia, PA
    kenwood_ka-4002_solid_state_integrated_amplifier.jpg

    Performed a recap and basic restoration on a small Kenwood integrated amp KA-4002 and it sounds great. The KA-4002 has a cap-coupled output, so it has a warm sound kinda like tube gear and very much so the "1970's vintage sound".

    • All electrolytic caps and "noisy" small signal transistors replaced.
    • Electrolytics caps in audio path replaced with Nichicon KL series or metalized film.
    • All replacement caps chosen for 70% working voltage (or lower) and for best price-point (i.e. if a 50V replacement was more expensive than a 63V one, then I chose the 63V one).
    • Output caps replaced with same-capacitance-value to maintain the design's same low end rolloff.
    • Added snubber caps to the power reservoir and output caps.
    • High-stress resistors (e.g. output transistor emitter ones) replaced with high wattage metal film resistors.
    • Rectifier bridge replaced with modern version.

    I built a larger spreadsheet with ALL caps, all resistors, all diodes and all transistors... just in case someone needs a reference or I get bored and OCD and replace everything with modern versions.
     

     

    Please register to disable this ad.

  2. dlucy

    dlucy dlucy67 (Doug) Subscriber

    Messages:
    2,112
    Location:
    Philadelphia, PA
    The BOM parts list for the recap and restore:

    Power supply

    C301 LKG1J472MESCCK
    C301(snubber) ECQ-E2104KB
    C302 ECQ-E2223KF
    C303 ECQ-E2223KF
    C311 667-ECQ-U2A104KLA
    D1 KBL02-E4/51
    R311 RN65D1002FRE6

    Tone amp

    Ce25 MKS2C041001F00KI00
    Ce26 MKS2C041001F00KI00
    Ce27 UKL1V100KDDANA
    Ce28 UKL1V100KDDANA
    Ce64 UPW1J221MPD
    Ce65 UPW1H221MPD
    Ce66 UPW1H101MPD
    Ce67 UKL1V470KPDANA
    Ce68 UKL1V470KPDANA
    Qe5 KSC1845FTA
    Qe6 KSC1845FTA

    RIAA or EQ or phono stage

    Ce1 ECQ-E1335KFB
    Ce10 UKL1V100KDDANA
    Ce11 UKL1V101KPDANA
    Ce12 UKL1V101KPDANA
    Ce15 UKL1V100KDDANA
    Ce16 UKL1V100KDDANA
    Ce2 ECQ-E1335KFB
    Ce69 UKL1J100KED
    Ce70 UKL1J100KED
    Ce70 UKL1V100KDDANA
    Ce8 UKL1V100KDDANA
    Ce9 UKL1V100KDDANA
    Qe1 KSC1845FTA
    Qe2 KSC1845FTA
    Qe3 KSC1845FTA
    Qe4 KSC1845FTA

    Main amp

    C121 UKL1H102KHD
    C121(snubber) ECQ-E2104KB
    C221 UKL1H102KHD
    C221(snubber) ECQ-E2104KB
    Ce45 MKS2C041001F00KI00
    Ce46 MKS2C041001F00KI00
    Ce47 UKL1V471MHD
    Ce48 UKL1V471MHD
    Ce49 UKL1V100KDDANA
    Ce50 UKL1V100KDDANA
    Ce51 UKL1J100KED
    Ce52 UKL1J100KED
    Ce55 UKL1V470KPDANA
    Ce56 UKL1V470KPDANA
    Ce57 UKL1J470KPD
    Ce58 UKL1J470KPD
    Ce59 FK22C0G1H224J
    Ce60 FK22C0G1H224J
    Ce61 UPW1J470MPD
    Ce62 UPW1H101MPD
    Ce63 UPW1H101MPD
    Qe10 KSC1845FTA
    Qe9 KSC1845FTA
    Re100 CPF3R47000JNB14
    Re91 CPF3R47000JNB14
    Re92 CPF3R47000JNB14
    Re93 CPF3R47000JNB14
    Re94 CPF3R47000JNB14
    Re95 CPF34R7000FKB14
    Re96 CPF34R7000FKB14
    Re99 CPF3R47000JNB14
    VRe1 3386W-1-102LF
    VRe2 3386W-1-102LF
     
    MaartenVB and Kyocerafan like this.
  3. dlucy

    dlucy dlucy67 (Doug) Subscriber

    Messages:
    2,112
    Location:
    Philadelphia, PA
    The before images:

    IMG_6294_AKsmall.png IMG_6334_AKsmall.png
     
    8xlaxx, MaartenVB, Kyocerafan and 2 others like this.
  4. dlucy

    dlucy dlucy67 (Doug) Subscriber

    Messages:
    2,112
    Location:
    Philadelphia, PA
    And the results:

    IMG_6355_AKsmall.png
     
  5. dlucy

    dlucy dlucy67 (Doug) Subscriber

    Messages:
    2,112
    Location:
    Philadelphia, PA
    Kyocerafan likes this.
  6. greenglass

    greenglass New Member

    Messages:
    1
    Location:
    West Hills, California
    Nice work sir. How many work hours to do it?
    I have 2, KA 4002's and 1, KA 2002. I do not have the skills to do what you do.
    I am looking for someone in Los Angeles to do some work if and when the amps need it.
    Thank You Sir
     

     

    Please register to disable this ad.

  7. dlucy

    dlucy dlucy67 (Doug) Subscriber

    Messages:
    2,112
    Location:
    Philadelphia, PA
    The KA-4002 has a very simple layout and is physically small. The replacements are very straightforward and easy to access. I'd say I could do all the parts above in just 4 hours. If I was doing just the recapping, it would be 2 hours.

    That being said, I'm just a hobbyist. A professional could have a completely different approach to work and billing.
     
  8. quaddriver

    quaddriver 120 What's per channel Subscriber

    I stumbled across this and am working a newer version of the 4002 (it says kenwood and not trio on it) I had to restore a channel thus far, besides the entire recap and the problems so far are the noisy/severely degraded 458's

    I have also done the bias trans and will be turning to the drivers as it has noise in it, like fm static. It might be the goofy protection circuit or that lone 2sc971 in the tone board - be interested in seeing what subs you have worked out.

    ETA: the static noise was in the 'protection'*(more on that later)

    my subs: Qe19 2SC734 --> KSC1815
    Qe17,18 2SC715--> KSC945CG (you can use a KCS945CY)

    * kenwood protection: in many cases on the older units is a solid state circuit with no relays that simply drains input signal to ground. I find on most, like 95% of the kenwoods that I get, that using protection - which does not means 'save the outputs' - eats itself in some way.

    Also, depending on which SCM you get D5,6 is listed as 1N60 in one, 1S2076 in another and the subs would be 1N60-99 for the former or a simple 1N4148 up to a 1N4007. using 'replace what you found' methodology, I used the Ge vs Si repalcements.

    Very clean sounding now. Gotta sub up the phono section and I think your KSC1845F across Q1-4 is ok.

    outputs ok and considering doing the drivers..they are not symmetric given that the amp is quasi comp. The 2SC1212A is a KSC2690 in my book. do you concur?
     
    Last edited: Jan 11, 2019
    dlucy likes this.
  9. MaartenVB

    MaartenVB New Member

    Messages:
    5

    Hi, new guy here. Sorry to kick this older thread. I have a ka4002 i want to upgrade/restore. I just started exploring the possibilities and expanding my extremely limited knowledge. Is it possible to sent your spreadsheet to me you mentioned in the first post? I think it will come in very handy. Thanks a lot.
     
    dlucy likes this.
  10. dlucy

    dlucy dlucy67 (Doug) Subscriber

    Messages:
    2,112
    Location:
    Philadelphia, PA
    AK doesn't allow XLS to be sent. I'll send you a PM.
     
    8xlaxx likes this.
  11. MaartenVB

    MaartenVB New Member

    Messages:
    5
    Many thanks Doug!
     

     

    Please register to disable this ad.

  12. quaddriver

    quaddriver 120 What's per channel Subscriber

    thats ok, I always append to old threads new info...Doug..pls send me a copy of your list too...Id like to compare...

    ps: more info for posterity...the Q3,4 2SC871 in the phono board (the non-a model) is 'B-C-E' if you are looking at the label. The KSC1845s we will use to replace as you know are 'E-C-B' (finding 2SC871 actual data is rarer than honest politicians. But the A model uses the 2SC1416A which we know is KSC1845 replaceable.)

    To get around the second stage possible having a higher hfe and since all my 1845s are F's, I used a matched set at hfe=371ish for Q1,2 and a matched set at hfe=402ish for Q3,4. Having 1000 on tape (literally I do) makes it easy to find ranges..

    I have finished the 4002 (but waiting for mouser to drop me some new 1000uf-35's in axial flavor for the cap-coupledness) and it sounds good on std input and really good and clear on phono.

    I have a different method to set idle - you can pin to R91/92 on the main board using the pins on the edge and since they are technically the ONLY resistors DIRECTLY affected by the bias I come up with 9.4mv across them (at .47ohm) to get 20ma reading. I find that the other pair will slight lag by about 1.5-2mv as this machine is NOT exact balance and you have to let it warm up a lot. when I got into setting it from the PS (previous service) there was 70mv across these resistors (yikes). Both the 4002 and 4002A have the same idle spec. I always try to set idle slightly lower than spec, but within 15%. But thats me.

    On and yeah, the goofy DPDT on/off switch suffers the same corrosion kenwoods love. D5 and a little q tip action get the smootchz out of the completely and utterly open switch.
     
    dlucy likes this.
  13. dlucy

    dlucy dlucy67 (Doug) Subscriber

    Messages:
    2,112
    Location:
    Philadelphia, PA
    For Qe20 on the tone board, I replaced the original 2SC971 with a KSC2331.

    For Qe17 and Qe18, I think you're right and KSC1815 or KSC945 are fine, just pay attention to he pi out order and buy the "C" center collector version if that matches better.

    For Qe19 I used KSC2383.

    For Qe13 and Qe14 where the original was 2AC984 or 2SC1212A, yes, I used a KSC2690 and that worked well.
     
  14. quaddriver

    quaddriver 120 What's per channel Subscriber

    For Qe20 I used a KSC2690AYS. the old 2SC971 had a heat sink on it and while the 2690 has higher ratings, I also added a copper To-220 heatsink from something I scrapped and it does sit warm, not hot, but warm.

    BTW - I messed up and since corrected it, I had listed Qe17,18 as 2SC871 cuz, well I had a brain fart, according to my notes it was was a 2SC715. hence my choice of the KSC945CG - the Ft was more in line. (I wanted to be higher, not lower than original)
     
    dlucy likes this.
  15. dlucy

    dlucy dlucy67 (Doug) Subscriber

    Messages:
    2,112
    Location:
    Philadelphia, PA
    MaartenVB likes this.
  16. quaddriver

    quaddriver 120 What's per channel Subscriber

    holy kee-rap....the replacements if you zorch the D155s are at best almost $11 each times 4...making a totally blown amp pretty much a total...
     
    dlucy likes this.

     

    Please register to disable this ad.

  17. dlucy

    dlucy dlucy67 (Doug) Subscriber

    Messages:
    2,112
    Location:
    Philadelphia, PA
    Good point. However, this is one of those applications where using a TO-220 instead of a TO-66 would give you modern, cheaper, better devices for a replacement.
     
  18. quaddriver

    quaddriver 120 What's per channel Subscriber

    good point...a couple (4) TIP40-somethings might do well here, prolly even re-use 95% of the heat sink...
     
  19. dlucy

    dlucy dlucy67 (Doug) Subscriber

    Messages:
    2,112
    Location:
    Philadelphia, PA
    I prefer the MJE150xx series (for no real reason), but I haven't used the 2SD155 specs to lookup which of the MJE's would work.

    For instance, if MJE15034 met the specs, then they'd be $1.31 each. Much more affordable.

    Edit: The MJE15028, MJE15030, MJE15032, or MJE15034 would all work fine.
     
    Last edited: Jan 14, 2019 at 7:11 PM
  20. quaddriver

    quaddriver 120 What's per channel Subscriber

    for no reason in partic, IIRC I saw that echo had once posted (and mebbe others) about sockets that accept the legs of a stock TO-220 and let you wire out the back? then just bolt the 220 to the sink using some mica and run the wires to the wires already there since the 66's are 'offboard' from the main board and away we go.

    We elect you to try it first :)
     

Share This Page