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Kenwood Model 650 Rescue

Discussion in 'Kenwood-Trio/Kensonic-Accuphase' started by gort69, Apr 14, 2018.

  1. gort69

    gort69 AK Subscriber Subscriber

    Messages:
    1,090
    Location:
    Vancouver, WA
    Bought this about 3 months ago - as usual I paid too much for it. The 650 is notorious for its scarcity and they seldom show up in any condition, this one being pretty much trashed. It was advertised as not working, no other details given. But it's a 650 and I saw potential.

    The left channel was blown badly. I have a feeling this thing sat in this state in a very dirty place for many years. I knew I was in for a big job when I removed the bottom cover and chunks of emitter resistors fell out, saw several parallel resistor repairs, 10,000uf filter caps in place of the original 18,000 uf-ers, a 33k ohm resistor where a 100 ohm should be and so forth.

    Here's the condensed version of the process - repaired the left channel, blew up the left channel again, repaired it again and made some upgrades, made exact same changes to right channel, then commenced with a complete overhaul and makeover.

    Pictures

    This is how it looked when I got it - notice the splotchy pink/purple fading to the "bronze" faceplate. Yuck. More on that later.

    P1011309.JPG

    Left channel damage - 3 of the 4 Sanken outputs blown, 3 of the 4 emitter resistors, plus board components. All 8 outputs were replaced with OnSemi MJ21193G/94G.

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    Repaired the damage, replaced all 4 emitter resistors and got the channel working. Ran it on the bench for a few days, then got the bright idea to try an ebay 2sb536 for one of the drivers that had blown originally. That lasted for about 20 minutes, then this happened. (lesson learned, no lecture necessary!)

    P1011360.JPG

    This took out 3 of the 4 OnSemis, a couple transistors on the board, and of course the ebay special. This is an early unit - serial # 330xxx. Later versions have this board with significant changes. Re 17,31 &32 were upped from 1/4W to 2W,the big axial cap Ce9 was eliminated and Re30 was replaced with a jumper. I upgraded the 3 resistors (3W), but left Ce9 as I wasn't comfortable eliminating it. All other resistors were swapped out for 1/2W metal film. The right channel got the exact same treatment.

    P1011368.JPG

    Once both amp boards were working properly, I moved on to the rest of the overhaul.

    Power supply rebuilt. The nice thing about this board is that it's easily removed from the amp. There is a lot crammed on to this little bugger. The regulators run wicked hot, so care needs to be taken not to lift a solder pad or two. I had one slightly lift but it didn't tear and I was able to save it.

    P1011369.JPG

    Tone and pre-amp boards recapped - no other changes made. This is when to do a thorough pot and switch cleaning. The bass pot on this was horribly dirty but was able to successfully clean it. Note the white trace outlining - later boards were dark green. Also, this one has the X08-1470-10 pre-amp board. Later models used a different board.

    P1011394.JPG

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    Contrary to popular belief, you don't have to unbolt and manipulate the transformers to replace the filter caps in these. This makes it very easy to get to the cap clamps and also easy to replace the relay and diode which are on the rectifier board. (clip the wires to the filter caps before getting the amp into this position - ahem)

    P1011380.JPG

    An overhead view of how grimy this thing was.

    P1011345.JPG
     
    Last edited: Apr 14, 2018
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  2. gort69

    gort69 AK Subscriber Subscriber

    Messages:
    1,090
    Location:
    Vancouver, WA
    Once the overhaul was complete and all adjusted and dialed in (it works flawlessly) I had to figure out what to do about the horrid cosmetics - the faceplate in particular Some would say say leave it be and clean it well and that it's part of the history of the unit, etc. I get that, but this thing was Fugly. The downside to dyed anodized aluminum is that it fades, esp the older stuff. I wanted to see if I could have it successfully redone. I searched online for anodizing shops in my area (Portland, OR). I found that most anodizers deal in large batches and won't do single items/small jobs. I couldn't find a single shop that would do bronze, which was my preference. I did find 2 or 3 shops that would do a single item. Since bronze wasn't an option (and I would not ship it to some remote corner of the country) I was pretty much left with leaving it as-is, having it done in clear anodize or having it done in black. Clear anodize was out, as that would would make it look just like a 600 and I already have one of those, so black it was.

    I didn't want to just take it in and have it done without knowing how it would turn out, so I took them a so-so KA-9100 plate to have done as a trial run. I also took my laptop along with photos of repro Marantz faceplates to show them the look I was after. They suggested that they could certainly do it, but that after they chemically stripped it that I pick it up and take it home and polish it, then bring it back for the anodize/dye/seal. The metal prep and finish has a huge impact on the final appearance.

    First thing to do is to remove the lettering - lacquer thinner and a toothbrush makes it easy.

    This photo is after having the original anodizing removed. I built a fixture from scrap wood to hold the thing and to act as a fence. I cut a chunk of 2 x 4 that slides exactly between the rails and stapled a piece of white 3M Scotchbrite (finest) to it. I lubed the thing with soap and water and had at it, keeping all of my effort in the horizontal to maintain the brushed finish. Once happy with that I polished it with Mother's aluminum polish, rinsed it off and too kit back for the anodize/dye.

    P1011411.JPG

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    Brought it back home and filled the lettering back in with white nail polish. I like like the look a lot.


    IMG_0709.JPG

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    This cost me a whopping $60 plus supplies. So I took the plunge and went through the same process on the 650.

    Here is a before photo of the "naked" 650 plate - you can see how badly faded it was. Fortunately, it was virtually free of scratches. It had a couple of edge nicks that I smoothed out prior to anodizing.

    IMG_0714.JPG

    And here it is reassembled to the amp. I'm very happy with the look. I will say that these pictures don't come close to doing it justice.

    IMG_0725.JPG

    IMG_0732.JPG

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    That's pretty much it. The top cover is in getting a satin black textured powdercoat done and I have to reinstall the bottom cover.

    Special thanks go to @hopjohn - as usual - for his fabulous 500 restore thread and his invaluable parts list, as well as putting up with my pestering via PM. To Electro-Chem Metal Finishing in Portland, OR https://www.electrochempdx.com/ and to @rjsalvi for not talking me into having it done in lime green :) And to Kenwood back in the day for using stamped and filled lettering throughout most of their lines.
     
    Last edited: Apr 14, 2018
  3. Grenadeslio

    Grenadeslio Super Member

    Messages:
    2,183
    Yowzaaaaaaa

    I like
     
  4. rjsalvi

    rjsalvi Well-Known Member

    Messages:
    537
    Location:
    San Diego, CA
    Red! ...not lime green! smh... :D
     
  5. Alobar

    Alobar Pulling out of the Last Chance Texaco.. Subscriber

    Messages:
    5,312
    Location:
    SE Alaska
    That thing looks awesome!!
     
  6. Felix123

    Felix123 New Member

    Messages:
    7
    Great job! I wish I was as ambitious as you ! I'll just be happy to get my KA 6000 recapped and working properly. If you don't already, you should offer up your services so we can save these pieces of musical art for the next generation ! ! !
    Felix
     

     

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  7. hopjohn

    hopjohn Silver Face Subscriber

    Messages:
    1,079
    Location:
    Dallas, TX
    Wow Al, truly, one of a kind. The amp boards were a heck of a wrestling match, but with persistence, as always, you came out on top. Thanks for sharing all the details of the anodizing, looks great.
     
  8. punprankster

    punprankster AK Subscriber Subscriber

    Messages:
    978
    Location:
    New Jersey
    Wow.o.wow.o.wow.o.wow.
    That is a thing of beauty.
    That bekongs in a museum of modern art.
     
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  9. oldboats

    oldboats Active Member

    Messages:
    116
    Location:
    Fargo, North Dakota
    I am impressed yet again. Stunning work.
     
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  10. theophile

    theophile Pheasant Plucker. Subscriber

    I agree with you. There will always be those who maintain that the original context is best. It is a fair thing to argue simply because in every other sphere original condition is a high priority for sale pricing. However, in this case you are merely satisfying yourself. Heck, under that circumstance, you could have had the faceplate powdercoated Ferrari Red with the lettering re-scribed. In other words, to please yourself, there are no wrong moves.

    Appearences are in the eye of the beholder but to me it is reminiscent of the Sansui black face integrateds of the mid '70s. Reminiscent. I don't think that I have seen the Kenwood Supreme Series knobs, switches and lettering look better in any other context. The contrast between the faceplate and the (cleaned and polished) knobs etc is absolutely gorgeous.

    Hat's off to you. A loving restore and a personal touch that has enhanced the unit. Bravo.
     
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  11. jackflack

    jackflack AK Subscriber Subscriber

    Messages:
    17
    Location:
    Antioch, California
    Looks like a Sansui now
     

     

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  12. dpdatl

    dpdatl AK Subscriber Subscriber

    Messages:
    610
    Location:
    North of Atlanta
    But better :rflmao: cuz its a Supreme. I am a little biased...
     
  13. dpdatl

    dpdatl AK Subscriber Subscriber

    Messages:
    610
    Location:
    North of Atlanta
    I would display that even it did not work. Thank you for sharing with us.
     
  14. oldboats

    oldboats Active Member

    Messages:
    116
    Location:
    Fargo, North Dakota
    Something worth checking out - since you are a person not afraid to tackle things yourself.

    Then you can do any color you can locate or mix dye for.
     
  15. gort69

    gort69 AK Subscriber Subscriber

    Messages:
    1,090
    Location:
    Vancouver, WA
    I thought about it! The equipment needed and the supplies are fairly extensive and I don't have any of it. Burners to heat the dye and the sealing baths, power supply, battery acid, lye, tubs etc. Then what to do with it when I'm done. This was kind of a one shot deal and thought it best left to pro. When I mentioned I'd thought about doing my self to the guy at the anodizers he only said 'We know a trick or two'

    But thanks for the reply! - I think I watched about 50 DIY anodizing videos on Youtube
     
  16. cnyel1967

    cnyel1967 AK Subscriber Subscriber

    Messages:
    1,013
    Location:
    Ohio
    I'm a sucker for the black faced with chrome knob Sansui's and many of the "Euro" black and chrome pieces and I have to say, had Kenwood actually sold a unit like this- I would have purchased one years ago! Love it.....great job!
     
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  17. fernarias

    fernarias Super Member

    Messages:
    1,097
    Location:
    Merced, CA
    I've always liked the gunmetal finish on these. Too bad they fade to that purple pink color that people call bronze (and black Yamaha's fading to purple, yuk). But this looks very nice and it definitely different than other kenwood 70s gear. Very good job and good price at 60 bucks. Now please post a picture of it sitting in it's rosewood case. You do have a nice rosewood case for it, yes?
     

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