Started restoration on my CA-810 !

Discussion in 'Yamaha' started by Bert 1100, May 16, 2017.

  1. amr2

    amr2 Active Member

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    It's not too much offset, but If you decide to change the diff par, remember to match the transistors.
     
  2. Bert 1100

    Bert 1100 Super Member

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    I'll definitely be matching the pairs, or I'll end up with more offset :D.
     
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  3. amr2

    amr2 Active Member

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    427
    :jump:
     
  4. Artie

    Artie AK Subscriber Subscriber

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    Wow! Great job. And the cool thing about it is that when you're done, you'll have one of the nicest integrated amps that money can buy.

    On a side note, it would be worth it to archive that regulator solder image. That photo will definitely be worth a thousand words when trying to explain to someone what to look for when finding bad solder joints.
     
  5. Bert 1100

    Bert 1100 Super Member

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    Yes, that image came out particularly well. Only an iPhone 4s, cropped image....I find the iPhone is particularly good at close-ups...
     
  6. Bert 1100

    Bert 1100 Super Member

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    I put in quite a few more hours this weekend, with good results !

    I got the new bourns trimmers. replaced the one I thought was faulty. The problem of the idle shooting up occasionaly stayed :(.
    Did some more poking around and looking....and found this :

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    everytime I touched R456, the relay would click into protection. So I removed the flame-proof sleeves of those resistors (they must act like an insulating sleeve as well, with more heat going into the PCB)
    So after that no more going into protection at the touch of the PCB, but my idle is still unstable. :(:(

    Hmmmm, I just went in and redid most of the solder joints in this area of the PCB, and the problem is GONE :banana: I hope for good. I guess there was a bad solder joint somewhere...
    The idle now adjusts well on both channels and is stable. I'm happy with the trimmers installed on the bottom of the boards, for both channels.

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    So the function board went finally back in. Look how much clearance I have between the shafts and the caps : :confused:
    And I had to put in a washer between the function board "case" and the chassis rail, to raise that part of the function board by a couple of millimeters.
    The main caps are 75mm tall compared to the 70mm originals.

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    So then onto the lights : bulbs changed for 5mm "straw hat" (= wider angle) warm white leds. dropping resistors changed to equivalent of 1.8 kOhm.
    Since originally there are 2 in series, I put in series a pair of parallel 3.6kOhm 1/2 watt resistors. That gives me 20mA (nominal for my leds) and a heat dissipation of 1.44 watts (IIRC) so I should be fine with four 1/2 watt resistors...
    The original sockets were used, if the led's leads are not as flexible as the bulb's, they are flexible enough :)
    I took out the blue filter, I like it much more like this.

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    So, I just had to put it back together and try it out :D

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    So what's left ?

    - I want to put in modern 5-way speaker binding posts.

    - I need to repaint the grills, there was some awful glue left on that came off only with acetone, and part of the paint came off as well :eek:

    - I might take the meters out again : one had some spots due to a solvent I think, and I polished it more than the other, and the one more polished is a bit more white (more "yellowed" plastic came off I guess), it's harly noticeable but I see it...:crazy:


    With a lot of the vintage gear, I have a problem with smells. This one got cleaned as deeply as possible, and it is much better than at the start, but there is still this smell coming off when warm. Just a "warm electronics" smell, nothing bad, I don't mind, but my wife does not like it. We'll see how it goes, I hope I will be able to have it regularly in rotation :(.

    Oh, and the sound ? I had it on for quite a few hours, but did not do much "serious" listening.
    But I can say it sounds really good. Very balanced, pleasant. Often straight after a recap I find amps and receivers too bright. Not this one. The treble is nice and open, with a good sparkle.
    Overall is is quite detailed but not agressive. The bass is just right.
    And I like the adjustable tone controls, even if normally I run things all "flat"

    The adjustable loudness, I never really appreciated...I find the bass and particularly the treble become much too accentuated as you go further from the flat position. Maybe I just don't need it in my system :dunno:, which is a good thing !
     
    Last edited: Jun 19, 2017
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  7. Oldsansui441

    Oldsansui441 AK Subscriber Subscriber

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    Nice work, it looks great :thumbsup:. I like your meter LED's. You must have very well matched speakers as l wouldn't mind a loudness control on my CA-2010.
    As for the smell, l don't think you will ever eliminate it entirely, all of my units have had that same smell to varying degrees.
     
  8. Bert 1100

    Bert 1100 Super Member

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    I did change the diff pair with matched ksa992, went from 20 and 25 mV to 10 and 14mV. Not perfect but good enough ?
    What do the experts think ? the old transistors have an hfe mismatch of around 20...
    The new ones are matched, around 410, difference of no more than 2.
    Should i make up pairs with maybe a mismatch of 10 hfe, then put them in one way or turned 180 degrees and see what I get ?
    Or is 10-15mV plenty good ? I know it IS good.
     
  9. Bert 1100

    Bert 1100 Super Member

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    Speakers are the Monitor Audio Silver RX6. I'm very happy with them. I don't feel their tonal balance changes much from very low volume to loud.
     
  10. Bert 1100

    Bert 1100 Super Member

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    That's what I think as well. I wish my wife did not have such a good nose :D. Basically that's why I could not use my (restored as well) CR-820...
     
  11. amr2

    amr2 Active Member

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    427
    IMHO 10-15mV is plenty good
     
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  12. Bert 1100

    Bert 1100 Super Member

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    From Echwars' famous thread on DC offset :

    If you read:

    0 - 15mV: Damn good!! If you read '0V', you may have a capacitor output, or your meter is set wrong

    So yeah, "damn good" is good enough for me !
     
  13. Oldsansui441

    Oldsansui441 AK Subscriber Subscriber

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    That makes sense that those would have good bass response with the amp set flat.

    I think the smell gives a sort of nostalgic vibe, is your wife into scented candles by any chance :D.

    As amr2 said, your offset is fine.
     
  14. zaibatsu

    zaibatsu Active Member

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    441
    Looks really nice.
    I've done the same with those resistors in the past, IMO the insulating sleeve usually does more harm than good unless it's really close to other sensitive components, as you said it just reduces air-dissipation and heats the PCB tracks instead. It's not crazy to re-do 100% of the solder joints in my experience, often they can look fine but have micro-cracks that create problems later or when the gear is moved.

    For smells, I've found that all foam/rubber parts (especially around the transformer and heatsinks) absorb the smells and dissipate the wonderful aromas as they warm up - it helps to spray those with isopropyl alcohol - or remove/replace entirely depending on how dedicated you are.
     
  15. Gregory

    Gregory Radical Lab Animal

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    Nice work! Just found this thread, and I have a CR-2040 here with very cruddy PCBs.

    How did the inside of the bottom cover look? Was there any rust or corrosion? If so how best to restore?


    -Greg
     
  16. Bert 1100

    Bert 1100 Super Member

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    The bottom cover was not rusted but the zinc plating had become very dull and dark, both sides the same.
    What I did was give it a brushing, with something similar to a wire wheel but with plastic wires charged with abrasive, mounted on a polishing machine ( that sanding wheel is meant for bringing out the grain in wood)
    So it's now nice and shiny and it looks like the zinc plating is still there to prevent rust. I did not coat it with anything.
    I treated the cover of the function board in the same way, there are a couple of pictures up in the thread.
     
  17. Bert 1100

    Bert 1100 Super Member

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    This is what I used to shine up the function board cover and bottom cover. It gives a nice brushed finish as well.
    The sanding wheel is plastic with abrasive, it is meant for bringing the grain out in wood.
    I did not coat the covers with anything, so fingerprints end up showing as darker spots when the zinc plating oxidises.

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    Last edited: Jun 26, 2017
  18. Bert 1100

    Bert 1100 Super Member

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    The top grilles are painted, just a wipe down with acetone (did not remove the old paint totally) and a few coats with an ordinary spray can (RAL 9006)
    They look nearly like new.

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    Also I did not mention I put in an IEC mains connector. And I do have a three-wire cord with the earth connected to chassis.
    I did this on quite a few amps and receivers and never had a single problem. With equipment this old I think extra safety is a good thing.

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  19. Bert 1100

    Bert 1100 Super Member

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    I have now put in new speaker terminals.
    They are Pomona 6883, mounted on an aluminum plate.
    The amp has been in my system for the past 3-4 days and I think it sounds really great.
    I tested it at 1khz on my 8 ohm dummy loads, it puts out 26.7 volts just before clipping starts, which means nearly 90 wpc, both channels simultaniously, nice !
    I still want to sort out the (very) slightly different level of light on the meters, I think I just need to check the exact positioning of the leds, they are shining in slightly different directions, enough to make a small difference....

    All in all, I'm very happy with this amp. And importantly, its smell is now low enough to make it living-room worthy !

    The only thing that is bothering me is a mechanical buzz / vibration from the transformer that is audible, especially if the amp is sitting on a resonant surface....



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  20. Mr. Yamaha

    Mr. Yamaha Not so much Yamaha lately... Subscriber

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    Awesome job! Good inspiration for overhauling my CA-810 :bigok:
     

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