CR-820 In for a dial string and other items.

Discussion in 'Yamaha' started by Blue Shadow, Apr 2, 2018.

  1. Blue Shadow

    Blue Shadow I gotta get me a new title

    Messages:
    19,365
    Location:
    SE PA
    First off, the dial string was broken an inch to the left of the dial indicator so it gets a new string. But to get there I have to get the tuning knob off (for other cleaning and such), while I wait for dial string to arrive.

    I have the two set screws out of the tuning knob and it damn near won't turn even with some oil in the grub screw holes. Prying with spoons will bend the faceplate. Dental Floss, not going to happen.

    Anything I can do to hasten the removal short of flame? Maybe soldering heat will work if i can get the iron in that space. Maybe I need some liquid wrench in the grub screw holes.

    This unit is from a smoking home so it needs to be pulled apart and cleaned and the string replaced then the switches need a deoxit treatment before I evaluate it. Relay clicked in 3 seconds and both channels had sound. Without a complete recap what will keep this unit running another dozen years? Maybe just that relay timing capacitor I've read about? Any other must do work other than a complete recap? Thanks.

    Please check back, I'll have more issues with this fine machine.

    Here is the victim:

    CR-820a.jpg

    CR-820b.jpg

    You can see it does need some cleaning.
     
    Last edited: Apr 2, 2018

     

    Please register to disable this ad.

  2. Blue Shadow

    Blue Shadow I gotta get me a new title

    Messages:
    19,365
    Location:
    SE PA
    OK here is how to get that damn tuning knob off. Although coming in and writing the above gave the oil a chance, there is nothing turning in that area.

    Remove the two screws holding the thin rod inside the tuning mechanism that connects the tuning knob to the counterweight. Rotate the knob and rod (remember this is stuck) separately from the counter weight and remove the counterweight. Now continue to rotate the knob against the resistance of the glooogrease used when the unit was assembled on the rod inside the brass bushing until the knob with rod comes out of the receiver. Now you can work on the tuning knob at the workbench in the metal, wood and auto shop and not on the electronics bench.

    In this lousy picture the counterweight has been loosened and removed, replaced for the photo op. You can see the rod that is not wanting to come out of the brass bushing, not shown, that it rides in. This rod needs cleaning and relube for another few years of smooth troublefree life. Sony used the same glooogrease on the STR-V4 that had the same problem but I think its tuning knob did come off.

    CR-820c.jpg
     
    Last edited: Apr 3, 2018
  3. Blue Shadow

    Blue Shadow I gotta get me a new title

    Messages:
    19,365
    Location:
    SE PA
    Now that the faceplate is off we can look over what is there. 40 years of dust that just settled into the unit. It needs a good cleaning. Maybe tomorrow if it doesn't rain too much, this is an outside job. Last pic shows that pink/purple 33µF/16V cap used for the relay timer. I guess that is getting replaced.
     

    Attached Files:

    Last edited: Apr 3, 2018
  4. Blue Shadow

    Blue Shadow I gotta get me a new title

    Messages:
    19,365
    Location:
    SE PA
    @avionic, are there any gotchas or special replacements that need to be done when recapping this unit? It is getting a full recap, cleaned, transistors reseated, and the other normal refresh steps. Recommendations welcome.
     
  5. avionic

    avionic " Black Knights " Subscriber

    Messages:
    39,311
    Location:
    Fort Dodge, Iowa
    Pretty straight forward.
     
  6. Blue Shadow

    Blue Shadow I gotta get me a new title

    Messages:
    19,365
    Location:
    SE PA
    Cap List cause everyone wants to see a cap list.
    1 each .1 50
    3 each .22 50
    1 each .47 50
    2 each 1 25
    11 each 1 50
    2 each 1BP 50
    3 each 2.2 50
    2each 3.3 50
    1 each 4.7 10
    1 each 4.7 35
    1 each 4.7 63
    11 each 10 16
    2 each 10 25
    1 each 10 35
    2 each 22 25
    1 each 22 50
    4 each 33 16
    3 each 47 6.3
    2 each 47 10
    2 each 47 16
    3 each 47 25
    1 each 47 35
    4 each 100 6.3
    2 each 100 10
    2 each 100 16
    2 each 100 35
    2 each 100 50
    2 each 100 63
    2 each 220 6.3
    3 each 220 16
    2 each 470 6.3
    1 each 470 25
    1 each 1000 50
    2 each 10000 50 these are 35 x 85mm and you won't find any like that. they are also 15mm spacing for the leads again NLA.

    Guess I'm going to go with a bit more on both voltage and capacitance for these big uns. This because many of the larger caps today are delivered at 10% lower than value, well within the ±20% range. The higher voltage is because we are using a bit higher voltage today than back when this unit was built. So a 12000uF 63V cap should be fine, just modding things so it fits.
     
  7. Blue Shadow

    Blue Shadow I gotta get me a new title

    Messages:
    19,365
    Location:
    SE PA
    Well the unit is coming apart nicely, once one figures out how to remove the glued in PS caps without breaking the board.

    The relay in this unit looks fresh. Here is a pic of one of the contact sets that close when the relay engages.

    CR-820k.jpg

    Clean enough to eat off of it, but it is less than ¼" in diameter.
     
    Last edited: Apr 4, 2018
  8. Blue Shadow

    Blue Shadow I gotta get me a new title

    Messages:
    19,365
    Location:
    SE PA
    Well over 80 caps replaced, large PS caps cobbled into the unit and the frame around them adjusted to fit. Changed the bias VRs and set the bias today, got the unit cleaned over the last couple days and will be putting it back together.

    Checked the main voltages, 27.something should be 30
    and the three 12 volt points were 11.8 or so and a ±12.28 I guess. Hope these are close enough for Yamaha word or do I need to make some changes in the other parts of these circuits? Upped the main caps to 12000/63 a small bump up from 10000/50 to account for the new caps ±20% and usually being on the lower side of the specified size. And they are a decent size, so they look right.
     
  9. Blue Shadow

    Blue Shadow I gotta get me a new title

    Messages:
    19,365
    Location:
    SE PA
    Restring this thing is a pain so far. Looking for hints and secrets. Maybe I just need to be better at using thread.
     

     

    Please register to disable this ad.

Share This Page