Another Kenwood KA-5700 Recap & BOM

Discussion in 'Kenwood-Trio/Kensonic-Accuphase' started by Spenser, Aug 24, 2017.

  1. Spenser

    Spenser AK Subscriber Subscriber

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    I have a good-condition, working KA-5700 purchased a few months ago from a Pittsburgh Antique Radio Society friend who had it in his possession for several years. He found it gathing dust on a shelf at the now defunct Mason TV Repair, Route 30, Irwin, Pa.

    Offset: L 10.0mV R 36.3mV
    Bias: L 34.0mV R 45.4mV

    Hopjohn, I thank you for your 3/12/15 thread "KA-5700 Poor Dynamic Range." Wondered if you could field a few questions.

    Others if you have time and interest, your observations and suggestions please.

    1. Would you still go 16V on substitutions for the 10V electrolytic capacitors? I started to select some 25V and thought to stop and ask what you think today.

    2. In my due dilligence on pre-amp -- obvious power-handlers looks like you opted for Nichicon PW (C3,4,17) .

    I was wondering what flavor you selected for emitter-related C11,12,15, 16. Are those KW's? Or what would you select today?

    Did you use KLs in the power amp C35,36?

    3. By the way beautiful-looking work. Super pictures. Other aesthetics aside, how do you pull off such magic-glue-removal results? It appears as if the brown gunk never polluted the PCB.

    4. If you were changing out the filter capacitors in the power supply, among the many purchase options what would you choose today? As you know the original manufacturer components are Elna 6800uF42V.

    Note: might keep the original filter caps if they test good; depending on what you and others think.

    Please let me know if it would be helpful for me to post schematics.

    Thanks.
     
    Last edited: Aug 24, 2017
  2. hopjohn

    hopjohn Kenwood Krazy Subscriber

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    Spenser

    1) It's kind of a catch 22. The 16V capacitors wont spec as well a 25v, but either are better than a 10v would be. Though, using a higher voltage cap means it wont meet it's working voltage threshold to perform in circuit optimally (which is apparently around 85%). Personally I'd take my chances with the better spec'd cap so I'd use either a 16v or 25v cap, probably whatever I had on hand.

    2) I'd stick with the leaded caps that I used back in that thread UFW1J682MRD or the KW UKW1J682MRD

    3) Use a good low ESR cap like a Panasonic FC at 3,4,11,12. Use a KL low leak at 17. Use audio/ film caps at 13, 14.

    4) To remove glue I use a Popsicle stick with a sharp widdled edge, a small pencil sized dowel rod with a widdled edge, or my longest fingernail and helluva lot of time and patience. It sometimes helps to soak the glue with alcohol or acetone to soften it. Just be careful not to scrub a wet area or it can remove the silkscreening. Just let it soak awhile and then dab up any excess wetness before you scrape.

    I took a look at the schematic. No need.
     
  3. Spenser

    Spenser AK Subscriber Subscriber

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    Hopjohn, thanks for all this. I appreciate your time and effort. Looking forward to trying Panasonic FCs. Ah I see on C17 why the KL series low leak. Take care.
     
    Last edited: Aug 25, 2017
  4. 8xlaxx

    8xlaxx Super Member

    Very timely post. I snagged one of these amps today along with the KT-5500 Tuner.

    Is there a possibility of @Spenser or @hopjohn putting together a parts list for Mouser or another company for these caps and parts?

    Thanks in advance.
     
  5. Spenser

    Spenser AK Subscriber Subscriber

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    Hey 8xlaxx, I'm going off on a tangent here as usual -- I have two of those tuners. Thinking of cleaning up one and doing minor modifications detailed on FM Tuner Info site http://www.fmtunerinfo.com. I'll post BOM soon (for KA-5700 electrolytic capacitors). -Spenser
     
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  6. 8xlaxx

    8xlaxx Super Member

    I'll look into that link for sure. Thank you @Spenser

    I hit up @EchoWars and @gort69 for some buying tips and cleanup help, etc. Nice piece of gear. Looking forward to putting it into service and your BOM here (when you complete it).

    Sorry if I hijacked your thread for a post or two,... please continue! :lurk: Will be watching with interest.
     
  7. Spenser

    Spenser AK Subscriber Subscriber

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    Kenwood KA-5700 BOM

    Schematic ID (space) Original Component Specs (space) Mouser Part # (space) New Component Specs

    Edited to include Hopjohn's changes.

    C3,4 22uF10V 647-UPW1C220MDD6 22uF16V
    C11,12 100uF10V 667-EEU-FC1C101 100uF16V
    C13,14 3.3uF25V 505-MKS2B043301HJSSD 3.3uF50V
    C17 47uF16V 647-UKL1E470MEDANA 47uF25V
    C15,16 330uF25V 667-EEU-FC1V331 330uF35V
    C33,34 100uF10V 647-UPW1C101MED 100uF16V
    C35,36 10uF25V 647-UKL1V100KDDANA 10uF35V
    C39,40 47uF10V 667-EEU-FC1C470 47uF16V
    C41,42 47uF50V 667-EEU-FC1J470 47uF63V
    C43,44 10uF50V 647-UES1H100MPM 10uF50V
    C55 10uF25V 647-UKL1V100KDDANA 10uF35V
    C56 330uF50V 647-UKL1H331KHD 330uF50V
    C73,74 47uF10V 667-EEU-FC1C470 47uF16V
    C77 100uF16V 647-UES1C101MPM 100uF16V
    C78 100uF16V 647-UKL1E101KPDANA 100uF25V
    C79 10uF50V 647-UPW1J100MDD 10uF63V
    C80,81 6800uF42V 647-UKW1J682MRD 6800uV63V
    C101,102 .47uF50V 505-MKS22.2/50/5 2.2uF50V

    D7 YZ-140 512-1N5244B 14V1/2W Zener

    RL1,2 24V Relay 653-MY4-02DC24 General Purpose Relay
    D16 1S2076 512-1N4148 General Purpose Power Switching Diode
    Q26 2SC1213 512-KSC2690AYS BJT NPN (Relay Transistor)
     
    Last edited: Sep 14, 2017
    8xlaxx likes this.
  8. hopjohn

    hopjohn Kenwood Krazy Subscriber

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    A few adjustments

    Cm55/56/78 Low Leak
    Cm35/36 Low leak or Audio grade

    I didn't check your uf and V values you'll need verify it based on INSTALLED values not the S/M parts list if you haven't done so. I assume you have since you have diameter measurements.

    Also note the original filter caps have a lead spacing of around 10mm, but there is some fudge factor there so the 12.5mm lead spacing of the new caps should fit snug, but will work.
     
  9. Spenser

    Spenser AK Subscriber Subscriber

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    Aha! Cm35/36 and Cm56/56 I suspected. Cm78 though? I'm curious the function this capacitor performs. Thanks!!
    Great point! (I hadn't yet.) Thanks!!

    Edit: Have since checked installed values and all electrolytic capacitors in the amplifier are as per the service manual parts list.

    One other question.

    If you could refer back to your original thread, was Echowars saying, of all the diodes, only Dm7 (YZ-140), might warrant replacement as a matter or routine? Just wondering; not saying I've heard that this diode is a common-failure-component or anything. Thanks.
     
    Last edited: Aug 27, 2017
  10. 8xlaxx

    8xlaxx Super Member


    @Spenser

    I have found that the one mounted in mine is totally clear and the inner workings can be seen.

    Please post pics of your step-by-step progress. Thank you!
     
  11. Spenser

    Spenser AK Subscriber Subscriber

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    Thanks, 8xlaxx. You helped me ascertain that the relay in mine is a different version; and that the ones in yours and Hopjohn's probably also are factory. Mine has a black cover. Yours and Hopjohn's are clear-covered.
     
    Last edited: Aug 27, 2017
  12. hopjohn

    hopjohn Kenwood Krazy Subscriber

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    Kenwood sourced relays from various manufacturers, but in any case they'll sometimes be black and sometimes be clear.

    Use a MY4-02 DC24 replacement

    I don't know what he was thinking in his response on that one, you'd have to ask him, but I'd replace the relay diode Dm16 1S2076 with a 1N4148 as well as the relay transistor. Qm26 2SC1213 with a KSC2690AYS.

    None of the other transistors used are on the naughty list so I'd leave them alone unless you run into high offset, which from your stated figures looks pretty normal for this amp. After working on three of them they were all close to the same as what you have. If you wanna be anal you can try gain matching Qm7/9 and Qm8/10 2SA640 with some ZTX795 (watch the pinout differences). I did that once with minimal improvement.

    Cm78 is a decoupling cap, probably not critical to be a low noise variety, but that's what Kenwood used in several of the 5700's I've seen, so why buck the trend?
     
    Last edited: Aug 26, 2017
  13. Spenser

    Spenser AK Subscriber Subscriber

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    Perfect. Thank you!
     
  14. Spenser

    Spenser AK Subscriber Subscriber

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    Just a post here to let any watchers know project still active. Mouser shipment arrived today. Appears -- at-a-glance -- to be in order. Cleaned up the unit a bit more. Now beginning to remove old components and see about cleaning off glue. Side Note: while awaiting parts did a little research and prepared draft BOM for Kenwood KT-5500 tuner recap. Thanks.
     
  15. 8xlaxx

    8xlaxx Super Member

    Thank you for posting the update!

    Both units and the potential recap for each are of great interest to me.

    :needpics:
     
  16. Spenser

    Spenser AK Subscriber Subscriber

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    Ha that's funny, 8xlaxx. OK. OK.

    Thanks again, Hopjohn, for the glue-cleaning tips. I found if I use a Q-tip and put a little isopropyl alcohol around the base of a glued-in-cap; let that work some while taking out some others; then circle back and very carefully work under the capacitor edges a bit where possible with an Exacto knife, razor blade (EDIT it has since been recommended and Iagree; keep blades away from PCBs); the isopropyl alcohol helps loosen and make it an easier job getting those buggers out of there. Then as you said a little ispropyl and carefully work on the remaining glue with a fingernail and other tools you suggested, after evaporated, so as not to damage the silk screening (see Hopjohn;'s advice above Post #2).

    I'm going to add here that "Maas metal polish," works wonders on RCA jack cleaning; and I believe keeps them that way for a while due to a lubricant-finish that lingers after buffing. See last picture below.

    IMG_20170909_190357263_HDR[1319].jpg IMG_20170909_191913924[1318].jpg IMG_20170909_191508203_BURST000_COVER_TOP[1317].jpg
     
    Last edited: Sep 9, 2017
  17. hopjohn

    hopjohn Kenwood Krazy Subscriber

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    Nice work!

    I wouldn't put a blade anywhere near a PCB, but I hear what you're saying about using the alcohol as an initial softening agent of the glue as a good idea. As long as you've got the leads WELL desoldered you should be able to gently rock a cap back and forth to work it loose of the board. You shouldn't need to do any cutting. Pioneer used glue that seemed to dry a bit stiffer so those can be a bit of challenge, but Kenwood glue seems a little easier to deal with.

    Your photo shows a DEC manufactured protection relay with their black covers. Just an example of something other than an Omron branded one being used as I referenced earlier in the thread.

    Something else you can play around with, if you want to experiment, is using a shield atop the acrylic meter assembly. What I've done in the past is use some heavy white card stock ( I think It was a backer board for a comic book to give you an idea ) traced and cut to match the shape. Once cut, neatly poke a couple holes where the light assembly mounts using the existing screws. All said it makes for better, more evenly lit meters and without making any bulb changes.
     
  18. Spenser

    Spenser AK Subscriber Subscriber

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    Thanks.

    I think you're right about keeping blades clear of any PCB. That was the cavalier coming out in me. Ongoing challenge I have.

    Nice idea on a way to get better, more even meter illumination. I will do a little experimentation. I like meters.

    Got ithe amplifier back together. Works. Sounds very good. Need to run it for some hours and see what it does. Check the bias and offset. For now I would say the draft BOM could be declared good.

    Still not sure whether going to change out the relay. I have a new Omron, and the associated transistor and diode.

    Say, you might have noticed D7-Zenner went on the BOM. 8xlaxx said Gort69 said it was something he would do.

    IMG_20170909_235754499_HDR[1324].jpg IMG_20170910_000128850_HDR[1323].jpg
     
  19. Spenser

    Spenser AK Subscriber Subscriber

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    Offset:: L 10 .0 mV R 36.3 mV
    Bias: L 34.0 mV R 45.5 mV

    i.e. unchanged

    My nearby record shop Northern Audio so far has been unable to supply me with a copy of an Iron Maiden. Any that come in go right back out. I may have to check in with the venerable Jerry's Records in Squirell Hill.

    Here is a picture of the amplifier running. Four or five hours now still sounding very good. I agree the improvement in sound quality is remarkable.

    I will now alter the title of the thread to include BOM for searchability

    Thanks again.

    IMG_20170911_204941586[1331].jpg
     
  20. hopjohn

    hopjohn Kenwood Krazy Subscriber

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    I would replace the relay as recommended by others. Why wouldn't you, if you have the parts? :dunno:

    Edit: I cant see with enough detail to be sure, but if you are using slo-blow fuses, those should be fast blow fuses.
     

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