Recent content by cuda440

  1. cuda440

    What's wrong with this picture?

    I could add some.
  2. cuda440

    What's wrong with this picture?

    I have a SX-636 that I can't sell at $250, forget $800.
  3. cuda440

    Amos AK "Sawdust" has passed away "Saddened"

    I will always cherish the case he made for my SX-1050. As I have said in other threads, it looks good enough to eat. It may well be the last one of those he made. God speed.
  4. cuda440

    Project: Yamaha CR-820 (Rebuild)

    Thanks for the BOM. I've been using it on a friends 820. My first Yamaha. Heads up to anyone working on one of these or something similar. There is a two piece "T" shaped frame on the underside that supports the two main boards. To gain access to some of the parts for removal it needs to be...
  5. cuda440

    Cuda's SX-636 #2

    It sounds great (of course!), but I won't be keeping it as I have an SX-1050 and an SA-9500ii as daily drivers. This is the second 636 I have refurbed. The first one I did last year is currently on BT, but not getting any love so I think it will be heading to CL shortly. Too bad, really, as I...
  6. cuda440

    Cuda's SX-636 #2

    I found another long post about an SX-636 from Feb 2020. Among the various issues in that post was the same problem with bias being out of range no matter the VR adjustment, though the error was more like 40mv (L) and 30mv (R). The last post concluded that it's probably okay to leave it as is...
  7. cuda440

    Cuda's SX-636 #2

    I am just finishing up another SX-636 and trying to dial in the bias to the specified 20mv. The best I can get to is about 26mv. Should I be happy with this or dig into why I can't do better? The whole unit has received the usual recap and new silicon. Could the new parts be pushing the...
  8. cuda440

    Prettiest SX Receivers?

    I have the SX-1050 as my main squeeze, but I'm now admiring an SX-838 that I refurbed last year (after a year+ wait for parts). After the refurb I ran it for a bit to confirm my work then set it aside waiting for my son to take it. He's not ready for it yet, but I recently brought it out for...
  9. cuda440

    SX-850 In The House! Recap/Restoration Ahead!!

    Well whatever they are, the 850 I did didn't have them. And my 1050 doesn't have them or molex connectors either, though the 1250 may have molex. I wish they all had some kind of quick disconnect mechanism for the power transistor assembly. Would make servicing much easier.
  10. cuda440

    SX-850 In The House! Recap/Restoration Ahead!!

    I restored on of these 3 years ago, but mine did not have sockets for the power transistor heat sink bank like what you show here. I have a 1050 as my daily driver and it doesn't have anything like that either. What does the receiving end of those connectors look like?
  11. cuda440

    Cuda's next SX-838, need help

    Put the resistors back in to run/rerun the previous measurements on Q8/Q10 and Q12/14. Q8b -> Q10b = -2.2 -> -2.8 Q12e -> Q14e = 0.0 -> .265. Wait. What?! This IS the bias measurement, the one that wouldn't budge off of zero previously. So Mark, your comment earlier "strong suspicion 0.5...
  12. cuda440

    Cuda's next SX-838, need help

    Life in the way again, but I finally got R42 and R44 pulled out. Both read .5 ohms.
  13. cuda440

    Cuda's next SX-838, need help

    I didn't time to pull the resistor earlier today, but will be able to get to it in the next hour or so.
  14. cuda440

    Cuda's next SX-838, need help

    I believe I followed your instruction: "be sure raising and lowering VR4 voltage has a corresponding voltage effect upon Q8 b to Q10 b and Q12 e to Q12 e" (meaning Q14e). The two cells in the lower right corner reflected varying VR4: Q8b -> Q10b = -2.2 -> -2.8 Q12e -> Q14e = 0.0 -> 0.0 (no...
  15. cuda440

    Cuda's next SX-838, need help

    Here are the results: I didn't vary VR4 when measuring zero ref'd Q8-Q14. The outlier appears to be Q12 emitter.
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