Help an Idiot not Destroy a Yamaha CR 2040

Discussion in 'General Audio Discussion' started by 0r0b0r0s, Nov 13, 2017.

  1. 0r0b0r0s

    0r0b0r0s New Member

    Messages:
    20
    Hi, I live in the middle of nowhere, with few options for fun, so when a post popped up on CL regarding a "barn find" Yamaha CR 2040 I was like, might as well look, the pictures are blurry but that's a beast to be respected. I ended up grabbing it for $75 because it was very dusty, very grimy, and none of the lights came on during a quick-n-dirty plug in.

    Well, what's the worst that can happen, except a hernia, because it weighs almost 50 pounds, and felt like much more because my arms resemble noodles on good days, and this wasn't one of my good days.

    I got it home, managed not to destroy it or myself getting down the very flexible wooden stairs (circa 1875 or so) leading to my dirt-floor basement, and there I actually had enough foresight to not place it right on the dirty workbench but first placed it on a pile of boxes, carefully laid down my best dirty rag, and THEN put it on the workbench.

    Whadda mess. I cleaned it as much as I could bear, jammed it into a safety outlet (trips if you breathe on it hard), threw on my cheap basement speakers that were $30 20 years ago, and used my phone as AUX input. I held my breath and pushed "On." Stuff happened. The input knob was missing so I had to flutter about, and used some pliers to get it rotated over. Boom, thar it was, sound. Fired right up, output, both channels. But no lights. Hmmm.

    Probably a fuse. It wasn't a fuse, all 3 I could easily find tested fine. I pulled one of the bulbs out; yeah, it was dead. That meant that all the lights were really dead (except power light/stereo mode lights). How much use was required to get into that condition? The other possibility is that it was left on 24/7 for a while and when the lights failed somebody stuck it in a closet for 35 years. I could see that as well.

    Anyway, I de-oxyed the hell out of the pots, found one possibly-broken push switch related to something I would probably never need, and wondered what I should do.

    The cover was nasty plywood and falling apart along one of the edges. And everywhere else. I glued it all up and clamped it.

    I ordered some replacement LED lights.

    Is that all I really need to do? Should I actually try to clean the interior, which risks me doing something stupid?

    Can I just replace the lights, put on the cover, give it a quick polish, and hook it up to my system? I don't care about "restoration" even a bit, as long as it works it's good. It's gonna live under my desk anyway.

    Is there something I should do / check or just blissfully continue to carry on?

    (clueless in the middle of nowhere)

    IMG_2208.JPG IMG_2208.JPG IMG_2208.JPG IMG_2207.JPG IMG_2203.JPG
     
  2. N8Nagel

    N8Nagel AK Subscriber Subscriber

    Messages:
    5,275
    Location:
    Sterling, VA
    I would download the shop manual and adjust amplifier bias and offset to spec. It's rare that a unit that old that has not been recently serviced is anywhere close to in spec.
     
    darkblue94 likes this.
  3. 0r0b0r0s

    0r0b0r0s New Member

    Messages:
    20
    I have a multimeter but have never adjusted bias or offset... can you point me to a place where I can read about it for the 2040 or the method in general?
     
  4. N8Nagel

    N8Nagel AK Subscriber Subscriber

    Messages:
    5,275
    Location:
    Sterling, VA
  5. 0r0b0r0s

    0r0b0r0s New Member

    Messages:
    20
    Thank you!
     
  6. N8Nagel

    N8Nagel AK Subscriber Subscriber

    Messages:
    5,275
    Location:
    Sterling, VA
    Also, grabber probes are your friends here. You do not want to be playing with 2x regular probes AND a screwdriver simultaneously, you only have two hands. Also multiple meters can help as you can then check bias and offset simultaneously and not have to hook/unhook stuff until you go to the other channel.
     
  7. Dingman

    Dingman Do you know where your towel is?

    Messages:
    1,816
    Location:
    Des Moines, Ia
    N8 is right - just do the simple bias\offset adjustments and call it good.

    If it's working OK for you, don't mess around inside - and like he said, be very careful making those adjustments - alot of people blow stuff up by slipping with an exposed probe.
     
  8. 0r0b0r0s

    0r0b0r0s New Member

    Messages:
    20
    If I don't care about using it as a tuner at all, do I still have to fuss with the bias/offset which sounds scary to me, because I'm really bad at all this stuff?
     
  9. petehall347

    petehall347 the brandy coffee man

    Messages:
    23,793
    Location:
    uk.. the middle bit
    keep a check to see if it runs hot or sounds bad ..if not leave well alone .
     
  10. N8Nagel

    N8Nagel AK Subscriber Subscriber

    Messages:
    5,275
    Location:
    Sterling, VA
    Those have to to with the amplifiers, not the tuner. I would not mess with any tuner adjustments at all because those require some specialized equipment to dial in, the odds of you making reception better are vanishingly slim and the odds of making it worse are pretty good.
     
  11. 0r0b0r0s

    0r0b0r0s New Member

    Messages:
    20
    Copy that. I'll look at the service manual and see if it seems scary; if so I'll just pretend I don't know anything about it.

    Is there some really basic test I can do to see if things are COMPLETELY whacked?

    Yeah I just looked at the service manual I'm not messing with that. Dummy loads, etc. Over my head. Plus it can kill me.
     
    Dingman likes this.
  12. N8Nagel

    N8Nagel AK Subscriber Subscriber

    Messages:
    5,275
    Location:
    Sterling, VA
    easy test: stick your meter probes in the "B" speaker outputs and set speakers to "A+B" with meter set to DCV

    Ideal would be a reading of .010VDC or less as a rule of thumb

    Alternately - a start up or shut down thump may be a sign of excessive offset (note: some older units will thump and that's just the way they are, but I don't think your unit should be a thumper)

    this only works on a non-cap-coupled unit but I believe that your CR-2040 falls in that category
     
  13. 0r0b0r0s

    0r0b0r0s New Member

    Messages:
    20
    There is a quite loud pop when I shut it down but I read somewhere that this is also an effect of having all the lamps burned out; they pick up or drain some of the excess current during shutdown. Well, that was the claim; I'm not saying it is true, but it might help after I get them replaced.
     
  14. 0r0b0r0s

    0r0b0r0s New Member

    Messages:
    20
    I'll do the test on the speaker outputs tonight; thanks; that's the level of testing I am capable of!
     
  15. eiraved

    eiraved AK Subscriber Subscriber

    Messages:
    1,380
    Location:
    Antelope Valley, CA
    Do you own an air compressor? Blow the dust out of the top and bottom thoroughly with the compressed air. You don't want any dust inside which could cause a fire when the receiver heats up!
    I believe you are correct there about the lights. If you plan on using the unit, but don't plan on changing those lights anytime soon, you need to save the speakers from that loud pop. Turning the volume to 0 or placing the speaker selection to "Off" prior to powering the system down will prevent that audible pop.
     
    Last edited: Nov 13, 2017
  16. Robisme

    Robisme Sansui Enthusiast Subscriber

    Messages:
    11,542
    Location:
    Martinez California
    Yamaha wired the lamps in series pairs, so if one goes out, so will its pair. So, all the lamps are most not likely bad, but should be replaced.

    You may want to see how the lights are wired and pick one set of pins for LEDs.

    There may be a service bulletin on the CR-2040 as well.

    Rob
     
  17. 0r0b0r0s

    0r0b0r0s New Member

    Messages:
    20
    hey I checked one of the b outs it is 203 mv dc is that ok the other one coming up sorry on phone


     
  18. 0r0b0r0s

    0r0b0r0s New Member

    Messages:
    20
    the other one says 107 mv dc gud enuff?
     
  19. wmgwizard

    wmgwizard Super Member

    Messages:
    3,137
    Location:
    Browns Mills NJ
    You may want to ask the mods to move this to the Yamaha board.

    Avionic and some other top notch guys hover over there and are a wealth of knowledge regarding Yamaha gear.

    Your DC offset is a bit high and may also be part of your turn off thump.

    Bulbs are wired series/parallel so one going out will make others not work. Not sure I'd recommend changing to LED's, they may collectively draw more current and cause other issues, that and they just don't give off that vintage glow.

    The 2040 is a workhorse and will serve you well once you get the bugs worked out.

    Be careful cleaning as the anodizing tends to flake off leaving silver "blotches".

    Clean the inside with some compressed air and a soft paintbrush to loosen the stubborn stuff.
     
  20. OMGCat!

    OMGCat! AK Subscriber Subscriber

    Messages:
    1,867
    Location:
    San Diego, CA
    You got a killer deal on that receiver for sure even if it's not in the best of shape cosmetically.
    The offset is a bit high but not too terribly so. The offset adjustment is the safer of the two if you only want to do that.
    The bias adjustment is where people tend to explode their amp because they didn't use grabbers and/or didn't read the manual before going in screwdrivers ablazin'.
     

Share This Page