CR1020 Restoration Guidance

Discussion in 'Yamaha' started by LFazio51, Nov 25, 2017.

  1. LFazio51

    LFazio51 AK Subscriber Subscriber

    Messages:
    207
    Location:
    Beaumont, Texas
    Hopefully that's not a "lurk" waiting for me to fail Bert!! lol! I'm sure I'll continue to run into more unexpected problems. Not the best design to "cut your teeth" on!
     
  2. Bert 1100

    Bert 1100 Super Member

    Messages:
    1,139
    Location:
    Planquiri, Switzerland
    Definitely not :(
    Just a very informative thread with great photos, that's all...:)
    Keep up the good work, we all learn from such threads, even the masters were happy to get a part number for the Molex header !
    :beerchug:
    Hey, it's no wonder a couple of traces lifted when you see how cooked the board is....
     
    Mrv8q and LFazio51 like this.
  3. LFazio51

    LFazio51 AK Subscriber Subscriber

    Messages:
    207
    Location:
    Beaumont, Texas
    Man it fits like a glove TOO! :banana: Can't wait to get it installed so you guys can check it out!
     
    Oilmaster likes this.
  4. Oilmaster

    Oilmaster Drillers do it deeper Subscriber

    Messages:
    1,130
    Location:
    Paris & The Hague
    This is BY FAR the best board I have seen; they are usually much much worse :(
     
  5. Oilmaster

    Oilmaster Drillers do it deeper Subscriber

    Messages:
    1,130
    Location:
    Paris & The Hague
    Hereby some photos of a CR-2020 PSU capacitor board in a more common state.
    This is from the CR-2020 that I fully restored (a full detailed thread will come sooner or later)
    A second used board that I bought off eBay was not much better....

    AK-18.jpg


    AK-19.jpg

    AK-20.jpg

    AK-21.jpg
     
    Last edited: Dec 18, 2017
  6. Bert 1100

    Bert 1100 Super Member

    Messages:
    1,139
    Location:
    Planquiri, Switzerland
    This was the board from a CR-2020 I did not long ago....I guess I was lucky :)
    IMG_3893.jpg
     
  7. Bert 1100

    Bert 1100 Super Member

    Messages:
    1,139
    Location:
    Planquiri, Switzerland
    :yikes: :yikes:
     
  8. Oilmaster

    Oilmaster Drillers do it deeper Subscriber

    Messages:
    1,130
    Location:
    Paris & The Hague
    Hereby an example of the TO-220 transistors (TR712/715) mounted on the chassis behind the VU meters.
    I am not happy with the wiring that I did.....they might have been a bit longer and smaller gauge.
    But it was the wire that I had in stock, and I had to return the unit to the owner.
    The wiring would have been redone more charming if I had the time.
    You'll need a shoulder washer under the screw and TO-220 SIL pad to isolate the metal back of transistors from the chassis

    Some AKer did it nice(r) using a PC board type 3-pin connector for a cooling fan; that may work out very nicely indeed :)

    AK-30.jpg
     
    Beau Geste, rottalpha and LFazio51 like this.
  9. Oilmaster

    Oilmaster Drillers do it deeper Subscriber

    Messages:
    1,130
    Location:
    Paris & The Hague
    You were ! ;)
     
  10. LFazio51

    LFazio51 AK Subscriber Subscriber

    Messages:
    207
    Location:
    Beaumont, Texas
    WOW! You really know how to make a guy feel lucky Avionic - and I mean that sincerely! :)

    Component Measurement & Testing
    I've still got to remove the 10k 1/2wt resistor and both 4.7k bleed resistors but after that, I'm moving forward with the installation of new components. If there are some measurements that should be taken on these diodes, please share now while the board is relatively free of most components.

    Lifted Pad Photo
    Also, I have to share the dam pic of the trace I lifted while cleaning!! I'm so pissed over that - it's such a rookie mistake!! That's my last forey into being a "bull in a china shop" on this one! :mad:

    IMG_0484.JPG

    Pad Bypass
    Ok, the attached pic below indicates the path I'm taking to mitigate one of these lifted pads. I'm pretty sure I'll be ok doing this but will need to remove the "jumper," open the pcb hole a little more, and re-install both the jumper and 33ohm resistor. The circle indicates the location on the trace side of the board where the pad is lifted. I'd like to get someone's blessing on this before proceeding.

    CR1020 E.Cap Bd. Pad Bypass.jpg
     
  11. Oilmaster

    Oilmaster Drillers do it deeper Subscriber

    Messages:
    1,130
    Location:
    Paris & The Hague
    It's not you, it's the rather poor board quality (it may happen with any other board in that unit, be aware).

    Regarding that track issue, I would scrape off the green solder mask from the failed isle toward the next isle (where the jumper arrives), install the new resistor at normal location, then bend the leg across the nude track and solder the whole thing up.

    If you are worried about that track coming off sooner or later, the trick is to 'squeeze' the PCB between two sides.
    Difficult to explain, but it takes a relatively cheap "lead forming tool" that creates a "kink" in the resistor's leg.
    When you then bend the leg on the solder side, the PCB is then squeezed between two sides of the leg.

    https://www.ebay.com/itm/1-pcs-Plie...231841?hash=item2848275fe1:g:T1kAAOSwcj1aIRsC

    (this model can be found half price elsewhere)

    Regarding the diodes: a serious assessment would take a load test, which will be out of your reach.
    But using the diode test function on a regular multimeter should give 0.50~0.60 volt in one direction only.
     
    Last edited: Dec 18, 2017
    LFazio51 likes this.
  12. avionic

    avionic " Black Knights " Subscriber

    Messages:
    37,355
    Location:
    Fort Dodge, Iowa
    Oilmaster.....
     
    Beau Geste and LFazio51 like this.
  13. LFazio51

    LFazio51 AK Subscriber Subscriber

    Messages:
    207
    Location:
    Beaumont, Texas
    Pad Bypass
    Here's a photo of the trace side just behind the photo where I indicated I was taking a "new route" with the 33ohm resistor.
    IMG_0483.JPG
     
  14. Oilmaster

    Oilmaster Drillers do it deeper Subscriber

    Messages:
    1,130
    Location:
    Paris & The Hague
    hmmm...

    will a challenge without rivets.....
     
    LFazio51 likes this.
  15. LFazio51

    LFazio51 AK Subscriber Subscriber

    Messages:
    207
    Location:
    Beaumont, Texas
    BTW gentlemen, I need to get some jumper wire. If anyone has some specs, ...well then, hook a brother up!
     
  16. LFazio51

    LFazio51 AK Subscriber Subscriber

    Messages:
    207
    Location:
    Beaumont, Texas
    As I sit and consider all comments in this thread, I can't help but wondering, AM I REALLY THAT LUCKY? :dunno: :whip: I'm still on the E.Cap board and one (and every AKer familiar) can only speculate what other obstacles will be encountered. I believe these units sound good but I'm not sure that they perform well enough to endure every difficulty they present when considering there are lots of good sounding receivers in this era. But as you indicated earlier, once I get to my Marantz 2265, LIFE WILL BE GOOD! ...if this unit doesn't become the reason I ditch the hobby first!! o_O
     
    Mrv8q likes this.
  17. avionic

    avionic " Black Knights " Subscriber

    Messages:
    37,355
    Location:
    Fort Dodge, Iowa
    I just use scrap component lead clippings.
     
    LFazio51 likes this.
  18. Mrv8q

    Mrv8q Well-Known Member

    Messages:
    616
    Location:
    Los Angeles
    You guys are scaring me with the pix of those boards! I will open my 1020 now with trepidation, but really,
    my hat is off to all who have posted, commented, advised, and taken great photos!

    Looks like it will be next year before I get back into my 1020 to heal a diminished left channel.(Already done the
    Deoxit shuffle).
     
  19. LFazio51

    LFazio51 AK Subscriber Subscriber

    Messages:
    207
    Location:
    Beaumont, Texas
    Power Supply C. Board -1: Proposed changes to TR712/715 for improved cooling
    Oilmaster and others have proposed and alternate location for TR712/715 to gain efficiency in cooling. This seems to be a very interesting modification considering the heat generated by both these particular components and overall design. And while the option to mount these just beneath the panel meters on the horizontal flat plate would appear to be a good one, it seems a location requiring less modification may be appropriate as well. This led me to consider the primary heat sink. It seems that if you could fabricate a bracket that would attach to the existing bolts, extend horizontally, then elbow down, so that the transistor could use the external surface for both a mount and cooling, you would improve overall cooling in a manner less invasive to the original design. Upon further consideration, I decided to make a quick prototype (see pics below) to get the old creative juices flowing. I took some scrap 1/8" aluminum, some quick measurements, and began to cut and bend. I was worried that the heatsink bolts would not be long enough to add another 1/8" created by the aluminum, but I was able to get a few turns and secure both the bracket and heatsink back to the frame. Unfortunately, 1/8" is the maximum height you can add, which leaves no room for anything isolating this bracket if desired.

    CONSIDERATIONS:
    This location appears to be extremely appropriate at first glance but I believe its necessary to consider the effects of heat developing from the main heatsink and its transmission to the bracket, ultimately heating the transistor. It seems obvious that the transistor rate of cooling would need to outpace the heat transmission from the main heatsink. I feel the design of the bracket, along with it's coupling to the main heatsink, can reduce or eliminate this issue entirely. An insulator of some kind inserted between the bracket and main heatsink would significantly reduce the transfer of heat. Adding additional surface area should also help the heat generated by the transistor AND heatsink for which it's mounted, cool much quicker, therefore, cutting some "fins" into the sides would seem appropriate (see hand sketches below).

    Overall, I believe this is a reasonable idea but am certain it can be better, especially with the input from those monitoring this thread. I also believe it makes this thread more interesting, which is always a good thang! Please understand, I'm well aware that these modifications are not nearly as necessary as those associated with the CR2020, I'm simply enjoying the hobby and viewing this modification as a way to build skills. Hopefully this idea will peak some interest and get everyone's creative juices flowing and the net result is something for all to use. So, please comment freely and provide as much direction and constructive advice as possible.

    Prototype Pics
    IMG_0491.JPG
    IMG_0492.JPG

    Hand Sketch of Proposed Changes
    TR712-5 Heatsink Mount.JPG
     
  20. LFazio51

    LFazio51 AK Subscriber Subscriber

    Messages:
    207
    Location:
    Beaumont, Texas
    Wow! That work is absolutely beautiful!! :bowdown:
     

Share This Page