CR-800 PSU Board

Discussion in 'Yamaha' started by cleverdick, Sep 6, 2017.

  1. cleverdick

    cleverdick Active Member

    Messages:
    183
    Location:
    Essex, UK
    Hi Yamahites,

    I have found an anomaly between the PSU schematic and the actual board - on which I would be glad to receive advice.

    Fusible resistor FR807 is shown on the schematic as 3R9, 1W, but on the board it's marked as 0.5W (in common with FR 804 and 805). The one currently in place is actually 4R7 (estimated 2W) and seemingly not fusible - being a reddish-brown colour. I guess this is non-original - although it does look Japanese - being marked RS2B 4.7 (ohm) K KOA.j.

    Obviously, I don't want to fit 0.5W if it's going to blow in normal use, nor do I want to fit 1W if it's not going to offer the requisite protection! (Basically, I'd like to see a photo of somebody's CR-800 PSU - which of course is the hardest board to get at.)

    Also, the four main fuses (F801-4): Would these be F or T-rated? The manual does list T fuses, but it's not clear if it refers to these, plus, it's unusual for output stages not to be protected with fastblow types.

    Cheers guys...

    Rich
     
  2. sssboa

    sssboa Active Member

    Messages:
    357
    pow1.jpg pow2.jpg pow3.jpg pow4.jpg
     
  3. cleverdick

    cleverdick Active Member

    Messages:
    183
    Location:
    Essex, UK
  4. cleverdick

    cleverdick Active Member

    Messages:
    183
    Location:
    Essex, UK
    Hey, that's really useful, I appreciate your time and trouble.

    Now, this is interesting because, on my board, the resistors are marked according to their power rating and not the fusing current, so I wonder which version came first? My schematic shows FR807 and 802 as 1W, the board has both marked as 0.5W, and your photo shows FR807 as 1W and FR802 as 0.5W (which in practice is the same as mine).

    Why did you do a re-cap? Was there a problem, or did it just seem like a prudent thing to do?
     
  5. sssboa

    sssboa Active Member

    Messages:
    357
    haha, I took pictures to remember how the caps go, I am happy you found the pictures useful.
    I recap now all gear I buy. Only one cap was certainly bad. If I remember well it was a single 47uF/80V. It showed 50% voltage loss, while all other caps up to 2%. Then filter caps were 4500uF out of 6800uF. Recapping tone board was a big task.
    Maybe you should look at the markings on resistors themselves, they are in mA. It can't be read from these low quality pics taken with a phone. I won't open the receiver any soon. Maybe around 6 weeks from now I will.
     
    Last edited: Sep 11, 2017
  6. cleverdick

    cleverdick Active Member

    Messages:
    183
    Location:
    Essex, UK
    I don't have the original resistors, it seems. They are fusible (being light grey matt, banded), with the exception of FR807. In other words, this one's been got at in a previous life.

    I only went this far having noticed a few fractured / dry joints on the wire terminations on this board. It was a noisy phono stage that started all this ;)

    Funnily enough, one of the transformer bolts is missing too!
     

Share This Page