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  1. dorke

    Amp In Protection Mode

    I think something bad may have happened to R629(1.5K) and/or R641(1.2K). Please disconnect the receiver from power. Measure the DC voltages on R629 and R641 and make sure it is zero! Only if there is indeed no voltage on the resistors check them in ohm(non-diode mode!). You can compare the...
  2. dorke

    Amp In Protection Mode

    You have the pins correct. I see you have re-measured Q609,the results are different(#9 vs #14). Please repeat the measurement another time so we know what we have. Q609 voltages are all wrong ! 11.82 V ==>E 14.10 V ==>C 12.61 V ==> B Q609 11.0 V ==>E 13.1 V ==>C 11.6 V ==>B The reading on...
  3. dorke

    Amp In Protection Mode

    Rick, What about the measurements in #10 ?
  4. dorke

    Amp In Protection Mode

    Q603 reads on its 3 pins... 0.72 V ==> E 1.33 V ==> B 44.9 V ==> C If these are indeed the "pin notations", then Q603 and the voltages on it are fine. Q609 voltages are all wrong ! 11.82 V ==>E 14.10 V ==>C 12.61 V ==> B Please verify the "pin" names as I noted them. Q609 looks to be...
  5. dorke

    Oh man...gotta love chinese sites...

    Here they are ;)
  6. dorke

    Battery charger circuit

    First question to ask is what is the voltage range allowable for your "digital" devices. For your circuit to work it should be something like 2.25-5.25V ,is that so? Second question is ,Do you need the entire "digital " circuit working when the USB isn't connected or just keep the RTC running...
  7. dorke

    Amp In Protection Mode

    As expected there is DC voltage on the output of the left channel AMP. Please put the volume at minimum and check the voltages on Q603 and Q609 relative to chassis GND.
  8. dorke

    Amp In Protection Mode

    Rick, you have counted the pins from the wrong side,it should be like that: 1) - 0.73 V 2) 0.03 V 3) 0.63 V 4) 0.00 V 5) - 0.74 V 6) I had to switch the meter to 200V & i got a reading of 44.1 V 7) 0.00 V 8) 0.58 V 9) 3.13 V There are some problems here: pin 8 (0.58V) is too low. pin 3...
  9. dorke

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

    O.K. Give us a call when you are back. The fuse will only blow if there is excessive current through it ,this isn't the case this time. The tuner issue may or may not be relevant,needs further investigation. When powering-up do you still hear the "relay click" ? Please check your speaker...
  10. dorke

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

    I have just noticed this. Well , Some info is found in the schematics, like part numbers of devices and some voltages. Other is analyzing the schematics and calculating/estimating. Others are "general expected values " of devices values like Si vs. Ger In general , I would say electronics...
  11. dorke

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

    When connecting the speaker wires, turn off the receiver to prevent accidental shorting with the speaker wires. When the speaker is already connected ,power the receiver up.
  12. dorke

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

    Not important,you can put the black probe in the middle.
  13. dorke

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

    That is good news indeed.:) When you power up the receiver you should hear a " relay click" after about 3 seconds or so. Does that happen? If so,put the volume knob at it's minimum , check the DC voltage(lowest range possible) on the "good "right channel speakers terminals(back panel). What do...
  14. dorke

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

    Looks much better. If you can , 1. Go over the entire board and inspect for bad solders,like the one you fixed. 2. Go over the entire board and gently remove all the solder "splashes "(red), especially near bare solder points,use a fine screwdriver or similar tool. Take care for them not to...
  15. dorke

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

    Needs some rework: Trying to read the PCB: Blue area- are the heat-sink pads-they are bad joints(lumpy ,not shiny),for this you should set the iron to 400C(probably with a 3mm tip if you have one,or a larger iron ). but are not very important ,as they have no electrical connections just...
  16. dorke

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

    Q617/Q619 are probably fine as well. Please re-insert Q631/Q633(in there correct location and orientation) and show a photo of the soldering work(top and bottom) . Re-connect(good solder joint) the cut transformer wires(2 grey and one green). Isolate them well, preferably with shrink tubing...
  17. dorke

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

    Q627/Q629 are fine as well, though you probably swapped the red and black writing on the previous post. Now lets test Q617/Q619.
  18. dorke

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

    Q631/Q633 are fine. Leave them out of the board for now. Please check Q627/Q629 in-board.
  19. dorke

    Miniature Speaker to Laptop Audio Jack

    The Laptop connector is of the stereo type (has 3 connections). You should use that type to connect to it properly,at the other end use only 2 of the 3 wires,one signal and one ground. Leave the other signal wire not connected.
  20. dorke

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

    Yes Z601,Z602 are fine. The diodes D615-D621 reading of .26 is low for a silicon diode, but these are OA99 germanium diodes,they are fine. Any progress with Q631/Q633 and Q627/Q629 ?
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