Help restoring a Yamaha CA-600

Discussion in 'Yamaha' started by EmuMannen, Sep 2, 2017.

  1. EmuMannen

    EmuMannen New Member

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    I was looking for a CA-800 when I stumbled across a CA-600 in really great condition.

    ca600-1.jpg

    I live in Sweden and this one had the European rear panel with DIN sockets. The only defect I could find was a broken tab of the PRE-OUT/MAIN-IN coupler and also the washer missing. Apart from that and some minor oxide in the controls it looked to be in mint condition so I bought it.

    ca600-2.JPG

    I have grown pretty fond of this little amp and have used it on a daly basis for almost a year now. It just recently developed a faint hum on both channels everything else seems to work. I guess its some failing component in the power supply. I have found no reason to open it up until now and I am now contemplating what else to do except fixing whatever cause the faint hum?

    I am a systems engineer by trade, I am a pretty good solderer and I got a really nice soldering station and access to most instruments needed to do electronics work. I am however no electronics engineer and I have always had a tough time to grasp the deeper knowledge needed to do proper electronics fault diagnosis.

    I got the CA-600 service manual and I am pretty sure I can disassemble and assemble it without doing harm. Identify components and follow instructions but that is about it. I really don't want to screw up this piece of hardware so I better ask for advice first than to learn as I go. That is why I turn to you guys for help. Any advice where to start, what to do and especially what not to do?

    Should I take the opportunity and replace all the caps because it’s a fairly old pice of hardware or just try to identify leaking ones? Any other components worth replaying when I got it disassembled? What about cleaning circuit boards and connectors? Is there a way to restore the original pots or should I just stay away from such endeavours?

    I also got a question regarding my rear panel. It looks legit and stock but the labelling of the input impedance selector does not match any documentation I have found on this unit. It is supposed to set something like 30kΩ/50kΩ/100kΩ or MM/IM/MI, but mine is labeled TAPE REC LEVEL, HIGH/LOW 2/LOW 1. So it does not seem to be an input impedance selector for the phono 1 input at all, it seems to be a tape rec level of some sort. Has anyone seen anything like that before? I haven't been able to find any documentation of this configuration for the CA-600.

    ca600-3.JPG
     
  2. EmuMannen

    EmuMannen New Member

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    31
    I have started to disassemble the unit and got some additional questions. I was trying to asses what has been done to it previously. It looks pretty clean and tidy inside and most circuitry looks untouched.

    ca600-5.jpg

    I just wonder if the original components where marked with the purple dots or if they are replaced parts (look stock to me)?

    ca600-4.jpg

    Some components might have run a bit hot though...

    ca600-6.jpg

    But what about this volume circuit board? Anyone know what the white-grey stuff might be and what to do about it?

    ca600-7.jpg

    Thanks in advance for any help...
     
  3. avionic

    avionic " Black Knights" Subscriber

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    We have fungus among us.....:biggrin: ( mold or mildew)
    Alcohol and a brush will take care of it.:thumbsup:
     
  4. zaibatsu

    zaibatsu Active Member

    Messages:
    393
    • If you like the amp and listen to it daily then it's definitely worth recapping, you'll notice an audible improvement
    • It's generally good to use slightly higher voltage rated caps (esp. since modern ones are physically smaller)
    • For the white-grey stuff I'd try isopropyl first, otherwise try acetone
    • Solder joints in high heat areas can crack/fail so it's good to check and touch up any cold / dull looking ones (at least)
    • This amp has some 2SC458LG transistors I believe (shaped like an outhouse) which are known to get noisy, you can use KSC1845FTA from mouser as substitute
    You can probably find a lot of info on all these topics here if you do a search, especially posts by avionic ^^
     
  5. EmuMannen

    EmuMannen New Member

    Messages:
    31
    avionic and zaibatsu, thanks a lot for your answers, will do...

    Everything is coming apart quite nicely. I guess this is a great opportunity to clean as much up as possibly. I found some grime around knobs and on the backside of the control panel. What is best used for cleaning up the aluminum front panel? I don't want to risk damaging the labelling etc.

    Additional questions:
    1. I guess from your answers that isopropyl is best used to clean up the circuit boards. Is is wise to go over all of them, not only the ones with fungus, mold, mildew or whatever I might find?
    2. How to best loosen caps "glued" to the boards?
    3. Recapping equals replacing all caps, every one of them, right?
    4. About the 2SC458LG transistors, turns out the service manual isn't so straight forward after all. I find a reference to at least one 2SC458LG for the Power Supply Circuit Board (7) in the parts list. But the list has a whole bunch of transistors listed and seems based on region (O or Y), (C or D), (D), (C or D), (B or C) etc. Ref No. is plank for these items so I don't know what parts they correspond to on the Power Circuit Board that seems to have at least 7 transistors, Tr701 to Tr707. I wish the parts list had a reference to these Tr701 to Tr707 but it doesn't. Am I missing something here?
     
  6. avionic

    avionic " Black Knights" Subscriber

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    Unsolder them. The glue is crusty and brittle by now so.just rock them back and forth. Then I usually just have a little scraping to do to remove the rest of the glue from the PCB. I find and exacto crafting knife with a straight blade works the best.
     
  7. avionic

    avionic " Black Knights" Subscriber

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    Your over thinking this..If it has C458 printed on it and looks like a little "out house" replace it with a KSC1815 which is and exact replacement. or KSC1845 which is not quite exact but does the job.

    [​IMG]
     
    Last edited: Sep 2, 2017
  8. EmuMannen

    EmuMannen New Member

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    Will do, thanks ;)
     
  9. avionic

    avionic " Black Knights" Subscriber

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  10. avionic

    avionic " Black Knights" Subscriber

    Messages:
    35,183
    Location:
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  11. avionic

    avionic " Black Knights" Subscriber

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    You will find your answer on the schematic. TR's are identified in various places(legends) within the schematic diagram.
     
  12. EmuMannen

    EmuMannen New Member

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    Im located in Stockholm, Sweden. ELFA used to be my drop-by place but they have now moved their stock out of Sweden. I now buy online from Farnell, Mouser or RS (all available here in Sweden for online purchase).
     
  13. avionic

    avionic " Black Knights" Subscriber

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    If your trying to develop a parts BOM using the service manual. They are loaded with incorrect typo's. Go with whats actually installed on your amplifier.
     
  14. EmuMannen

    EmuMannen New Member

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    31
    Thanks for the advice. Had to stop working on it to attend a family dinner. I will hopefully manage to disassemble it all tomorrow. Seems like all boards are connected to each other with no connectors except towards the rear panel. Do I keep them connected to each other or should I desolder them to be able to handle each board by it self? I will let this take the time it deserve. I think I will go board by board and work up a BOM as I go.

    Got to appreciate the build quality of these old amps. They don't make them like that anymore...
     
    Last edited: Sep 2, 2017
  15. EmuMannen

    EmuMannen New Member

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    Ok, managed to get it all apart and I am now contemplating how far I should take this? I have no idea how to disassemble the main amp units. Looks like I have to desolder the transistors Tr613 and Tr 615 or are the pins from the board fitted into sockets on the transistors so that I can just pull the board apart from the heatsink where the transistors are fitted? No way to get to the back side of the board otherwise. Found some additional "fungus" but no leaking caps and all solders looks solid. The unit is fully functional so I guess my options are:

    a. Clean everything up and put it all together again and hope for the best.
    b. Desolder each board from the lead cords, work board by board and replace all caps and other components that would be beneficial to swap out.

    I am just afraid that I might break something if I attempt option b.
     
  16. zaibatsu

    zaibatsu Active Member

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    393
    I have no direct experience so can't say if this model has sockets or directly soldered transistors (maybe someone else can tell you, or you can shine a torch in and see), but it's not a big deal to desolder them if needed anyway - just make sure you suck all the old solder off to reduce the chance of trace damage.

    It's up to you if you bother recapping the unit - personally I'd make the decision based on how long you plan to keep it - if you still plan to get a CA-800 maybe it's worth saving the efforts for that, but if you're going to keep using the CA-600 on a daily basis for years to come then certainly it will be worth putting in the time.

    For reference - capacitors in these units don't often leak, but can measure high in ESR and low in capacitance without visual indication.
    If you wanted you could just try rebuilding the power supply section alone to see if it kills the hum. It could also be a poor ground solder connection somewhere.

    If you are careful I don't think you'd damage it.
     
  17. EmuMannen

    EmuMannen New Member

    Messages:
    31
    Thanks zaibatsu, I plan to keep this unit even if I find a CA-800. I also thought about just rebuilding the power supply section but it would be a shame now when it's all in pieces. I just want to keep it as original as possible. It seems like no ones been poking around in this one since it was new. I just love the way the cables been put together with some transparent cord and tiny tidy knots. My plan of attack is to desolder each board from the cable harness (and try to keep the way it's bundled up) and then work on each card individually. The only thing that scares me a bit is how to get to the backside of the main amp unit boards. The Service Manual list Transistor Socket and Transistor Pusher as parts of the Main Circuit Board. I guess the the pusher is either whats pushed into the sockets for Tr613 and Tr615 (or the one pushing Tr607 against the heat sink at the bottom of the board) and I hope the socket refer to sockets for Tr613 and Tr615, but there are no ref number or amount in the BOM just some Japanese scribbling in the remarks column. Its hard to make something definitive out just peeking between the board and the heatsink. What do you guys think based on these images?

    Solder joints of whatever connects the transistor with the board
    IMG_1834.JPG

    Heatsink and transistor
    IMG_1832.JPG

    Peeking between the heatsink (left) and board (right) closeup...
    IMG_1830.JPG

    Peeking between the heatsink (top) and board (bottom) closeup...
    IMG_1827.JPG
     
  18. willyrover

    willyrover Super Member

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    The sockets are circled in red. My guess is the "pushers" are the ones circles in green. They might unclip from the board?
    Removing the output transistors from the heatsink (And from their sockets) should allow the board to separate from the heatsink. Be careful with the ones circled in green making sure they are also free of the heatsink.
    IMG_1830.JPG
     
  19. EmuMannen

    EmuMannen New Member

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    31
    Thanks willyrover, pretty much what I suspected and I think I understand how to break the main boards apart now. I have started to desolder the board from the cable harness. I started with the three easiest ones but only managed to clean up two tonight. It takes way more time than I thought. The boards look quite neat at a first glance but they turn out to be quite dirty as soon as you start cleaning them. They sure didn't hold back on solder during the 70ts! It takes forever to remove whats left after I have desoldered the cables...
     
  20. EmuMannen

    EmuMannen New Member

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    31
    First card that I managed to clean up, the volume control card, nothing else to do with this board, right?

    IMG_1921.JPG IMG_1922.JPG
     
    Last edited: Sep 3, 2017

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