Search results

Search Forums New Posts
  1. dorke

    Pair 2 Analog to Digital Converter Chip

    You can do it with a single ADC ! What you need are two " SaH(Sample and Hold) circuits" . You trigger them both at the same time and the points you sampled are frozen for you to measure with that single ADC.
  2. dorke

    List of older 74xx devices

    Many,if not most,are obsolete parts. Anyways, you should designate the parts as 74XXXXXX (six Xs!), to cover families like HCT ,ALS ,LVT , ALVT , CBTLVD etc. see details here under technology. and here a 2016 very useful Logic devices selection guide.
  3. dorke

    Technics SA-828 Receiver from 70s- Is it worth trying to save this aging patient?

    Iceman,I'm back. I shall have more time for a while. About the SA-1010. It is a more complicated unit,it has a uC in the loop for setting the final stage into proper working conditions (a "pre-heat" state). But in general the work on the SA-828 may help. Just to be come back on the same...
  4. dorke

    Technics SA-828 Receiver from 70s- Is it worth trying to save this aging patient?

    Hi Iceman, I'm very busy lately. My apologizes on the delay,it will take some more time,hope you have the patience.:( BTW, I have just got a Technics receiver model SA-1010 ,it is a 120W monster(the bigger brother of the SA828). Guess what? It has one working channel(great sound) and one bad...
  5. dorke

    Technics SA-828 Receiver from 70s- Is it worth trying to save this aging patient?

    The issue of replacements isn't that simple: 1. There are Trs which must be complimentary pairs i.e if you don't have one of a pair you have to replace both with another suitable complimentary pair. The pairs are: Q635 and Q637. Q631 and Q633. Q627 and Q629. Q623 and Q625. 2. The "suffix...
  6. dorke

    Technics SA-828 Receiver from 70s- Is it worth trying to save this aging patient?

    Nothing suspicious in the photo of the speakers terminals. Yes,please provide links to the devices offered . Please post a photo of the original Trs,so all part number detailed may be viewed clearly. I will go over them next week.
  7. dorke

    Technics SA-828 Receiver from 70s- Is it worth trying to save this aging patient?

    Cleaning=using Deoxit on contacts of switches, pots etc. The quick twist-type speakers terminals are known to cause problems. Can you post a photo? Cleaning them may help. Go over the solders with a magnifying glass,any suspicious point should be re-soldered and/or cleaned with a cotton swab...
  8. dorke

    Technics SA-828 Receiver from 70s- Is it worth trying to save this aging patient?

    Well, I agree with you on # 163 ,but it looks like that isn't the case here as per previous posts. The problem is intermittent indeed. IC 1002 is the device that monitors for "faults" and puts the receiver in protection if one is found. There is a test point(on the board containing IC1002)...
  9. dorke

    Technics SA-828 Receiver from 70s- Is it worth trying to save this aging patient?

    Yes, Aux and Phono have different paths in the receiver. Plus, the phono itself can produce problems (needle /dust etc.). So let's stay with the AUX alone for now. You should verify that the right channel performs well in all conditions: Try changing/playing with output related...
  10. dorke

    Technics SA-G90 With "Overload" message.

    You may get help from Technics-US here
  11. dorke

    Technics SA-G90 With "Overload" message.

    Is this model SA-G90,the correct one? Google doesn't find anything like it.
  12. dorke

    Amp In Protection Mode

    That is nice to hear.:) Our work here is done ...at last.
  13. dorke

    Amp In Protection Mode

    Is that the mid point voltage? What about the "4 resistors" voltages? Edit: If these are the resistors voltages,your amp should play well now. You can try it with music and speakers,at low volume first then crank it up.
  14. dorke

    Amp In Protection Mode

    At zero volume. And after 5 minutes warm up. Try trimming the left channel down closer to the right channel reading with VR601. Then remeasure R645,R647 voltages relative to R646,R648 voltages.
  15. dorke

    Amp In Protection Mode

    Minimum volume=zero volume=no volume. One more thing I forgot to say, let the amp worm up for about 5 minutes before you take the readings.
  16. dorke

    Technics SA-828 Receiver from 70s- Is it worth trying to save this aging patient?

    The relay should click . No speakers for now.
  17. dorke

    Amp In Protection Mode

    Rick , I would check again the center pin of the white resistors, DCV(200mV range) relative to GND for both channels. The left channel readings above are a bit un-equal. What do you get?
  18. dorke

    Technics SA-828 Receiver from 70s- Is it worth trying to save this aging patient?

    Yes, you should be able to hear the speaker. When in protection mode, please measure the voltages relative to GND on IC1002,it is a 9 pin single-in-line package,no prob slip! This IC should be found on a little board called SUP22910B. What is the pair they offered for Q631/Q633? About the...
  19. dorke

    Amp In Protection Mode

    Rick, Only at minimum volume please ! You have marked the resistors the wrong way ! For the left channel you have a single white resistor , Measure with both probes on R645 then both probes on R647 they should be both on that same resistor. For the right channel you have the other single...
  20. dorke

    Technics SA-828 Receiver from 70s- Is it worth trying to save this aging patient?

    Q633 is blown, Q631 looks fine but please remove it(if you didn't already). Q631and Q633 should be a matched pair ,so if Q633 original can't be found both should be replaced. DCV on IC601. Please look at #147, regarding the schematics as well.
Top