C-85 RCA upgrade

Discussion in 'Yamaha' started by stoutblock, Jun 6, 2012.

  1. stoutblock

    stoutblock If it sounds good, it is good... Subscriber

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    Yamaha C-85 RCA upgrade

    I completed the upgrade of the RCA terminals on my C-85.

    It's not that hard but very time consuming. The original terminals are the weak link on these early Yamaha Preamps IMHO. If you use tight interconnects you can pull the original terminal ground sleeves off in a snap. I have also seen these get loose over time and even standard interconnects will cut out if you wiggle them.

    This is a great upgrade modification and this C-85 sounds very solid now. You have to slightly drill out some of the holes in the PCB for the wire to replace the original bracket mount. I used AWG 21 cast copper wire. It is important to ground it just like the stock setup. You will also need to run a new ground to the rear plate and the PCB.

    These RCA locations are very close together but there is still room for most RCA interconnects. Depending on the terminals you are using, the isolation washers need to be trimmed very slightly.

    Next will be my C-2X but I will be using even better terminals and wire on that modification. It is basically the same setup as the C-85.

    [​IMG]

    [​IMG]

    [​IMG]
     
    Last edited: Jun 5, 2013
  2. elrod

    elrod AK Subscriber Subscriber

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    Looks fantastic. You did a great job on it! Love to see it on you C-2x when your done.
     
  3. stoutblock

    stoutblock If it sounds good, it is good... Subscriber

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    Thanks. I have to say that I think the Pre sounds better with the mod. It might be my imagination but I would characterize it as more revealing. The C-85 is a decent pre in the first place so this was well worth the work. Due to the quantity of connections I could not see using super high end connections but I have no complaints.

    Waiting for the wire (VH Audio's UniCrystal OCC) for the C-2x (Friday) and I think it deserves some better connectors (CONNEX-53451). I will also post some pictures when it is done.
     
    Last edited: Jun 6, 2012
  4. tubed

    tubed Lunatic Member

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    Wonderful job!
    Both my C-85 and C-2 have RCA issues, cold solder???
    I'd love to attempt a replacement like yours but wonder at my level of acuity at such an attempt:)
    Where on the PCB would I attempt solder re-flow for a temporary/permanent fix?
     
  5. stoutblock

    stoutblock If it sounds good, it is good... Subscriber

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    Typically the problem is not on the PCB attachment. It is in the RCA fitting itself. There is a mechanical join between the ground shield and the bracket that works loose. You need to desolder the whole bracket itself from the PCB and toss it. Then install new RCA terminals directly to the back plate and wire to PCB. This might seem extreme, and purists might cringe, but the stock RCA terminals are a POS. These Pre's are worthy of much better...

    [​IMG]

    (Picture from Mark's C-2X)
     
    Last edited: Jun 7, 2012
  6. Chris Brown

    Chris Brown AK Subscriber Subscriber

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    Very informative pictures.

    I have a C-80 and it has a few jacks on the back that are intermittent. Luckily for me they are on the inputs that I don't use at the moment, but it still makes me wonder when one of the jacks that I actually use will begin to experience problems.

    Are the stock jacks unworkable? No one would argue that your hard work is a solid upgrade over stock, but in my case, the difference between fixing the existing jacks and doing a repair on the level of yours would likely exceed my soldering skill threshold.
     
  7. pfcs49

    pfcs49 Phil Subscriber

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    Eagerly anticiPating the C2-X

    Having re-soldered both my C85and my C2-X I'm real interested to see how you make out with the C2-X. You can break trail for me! It will be quite interesting to see how viable this is to do on the C-2x. Good luck!
     
  8. stoutblock

    stoutblock If it sounds good, it is good... Subscriber

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    I don't think there is much you can do with the stock jacks. Even if they are working, you have to wonder if the mechanical connection can perform as well as a direct solder connection? A little corrosion and you would think there could easily be some fidelity limitations? I don't see how you can get in there and solder the mechanical connection? I use the Radio shack de-solder tool (with the bulb) and the old jacks come right out with a little wiggle and pull. I use a dremel 3/32" engraving cutter (111) to open the holes. Just twist it with your fingers (don't use the dremel as it could be too aggressive). I tin the tips of good 21 AWG wire, tin the RCA connections, then join. The grounding grommets are a little tricky. To match the stock setup each phono RCA needs to be grounded directly to the PCB. I solder the wire to the grommets first and then install the grommets. On the other connections you can ground both the left and right together for each pair. I made a little assembly jig that matched the Yamaha spacing and soldered each pair of grommets together before putting them on the terminals. It is crowded once the RCAs are installed so do as much work before assembly as possible. Installing the RCA and getting the nuts tight and all aligned takes a couple of beers. Once you have the back panel all complete then install to the case. Use tweezers to get the wire into the PCB holes. Again tin the wire first. Solder on the backside the wire to the PCB just like you would anything else.

    The C-2x is the same exact job as the C-85 (and C-xx for that matter). I already removed the old jacks from the PCB and installed the new jacks on the back panel. Just waiting for the wire (should be today). Again, I will post pictures when I am done.
     
    Last edited: Jun 8, 2012
  9. pfcs49

    pfcs49 Phil Subscriber

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    Both of my preamps had cracked joints at the circuit board.
    It's been five years since I did the resoldering but I recall that the C2-x was very inaccessible. But I've been wrong before!
     
  10. lunchbox22

    lunchbox22 Well-Known Member

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    What diameter wire did you use to connect the jacks to the pcb?
     
  11. stoutblock

    stoutblock If it sounds good, it is good... Subscriber

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    AWG 21 cast copper wire
     
  12. brutal

    brutal YamaHoarder

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    Nice work, but the mismatched jacks would bug the shit outta my OCD tendencies.
     
  13. lunchbox22

    lunchbox22 Well-Known Member

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    Thanks! Any suggestions as to where to source some of that cable? I've only found two places, both of which want 10 bucks to ship 1 foot!
     
  14. stoutblock

    stoutblock If it sounds good, it is good... Subscriber

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    that's what I get for buying in bulk!

    [​IMG]
     
    Last edited: Jun 19, 2013
  15. bob06

    bob06 Addicted Member

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    I change all the rca's on my C-4. The C-4 has lots more room.
     
  16. stoutblock

    stoutblock If it sounds good, it is good... Subscriber

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    http://www.vhaudio.com/wire.html
     
  17. stoutblock

    stoutblock If it sounds good, it is good... Subscriber

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    The C-4 has much better RCA terminals than the C-85, 80, etc. It is the direct connection to the PCB that is mostly at fault (which the C-4 does not have).
     
  18. Audio Fan

    Audio Fan First Class, Second Hand Subscriber

    Was just wanting to see what options are available for address the shortcomings of the C-80 and found this thread. Any chance the pics can be reposted?
     
  19. stoutblock

    stoutblock If it sounds good, it is good... Subscriber

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    Give me a few days to see if I can find them.
     

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