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  1. dorke

    Trying to make a transistor cancel another transistor

    David, Please explain in plain words what is it you are trying to do and for what purpose. That is the only way to give you productive and meaningful help . BTW, I think stopping this time-wasting "game of guessing" is a worthy goal as well ... o_O
  2. dorke

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

    O.K. Please add the IC601 DCV tests. The list looks complete by now. You should contact Digikey for checking/resolving the Trs suffix issue. Then we shall approve the final list before purchase. When the parts do arrive, we shall re-construct(literally) the bad channel step by step from "left...
  3. dorke

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

    Here it is.
  4. dorke

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

    O.K All Trs and Diodes look fine. Including Q609 which has it's B and C wired together in the circuit, and D615/D617 which are Germanium ones. Q607 is a 5 pin device(dual Tr),so it's measurement isn't complete here, but I believe we have checked it before. 3 more resistors need to be replaced...
  5. dorke

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

    O.K Please check R651 and R653 as well.
  6. dorke

    Trying to make a transistor cancel another transistor

    "cancel",like matter and anti-matter ;) What are you trying to achieve?
  7. dorke

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

    Yes,gold is indeed 5%. Please check R659 and R661 as well.
  8. dorke

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

    Just to be on the safe side. I would re-check all "surviving Trs" : Q605,Q607,Q609,Q611,Q615 and diodes: D603,D605,D607,D611,D613,D615,D617.
  9. dorke

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

    Yes 1/4 is indeed 1/4 watt. We need to know the accuracy of the resistors,could you please post a pic of the corresponding resistors of the good channel. Resistors can be bought from any manufacture (unless they are very special type) from Ebay as well. Please check the following as well...
  10. dorke

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

    For Q625,Q623 we can use suffix "S" (or "T") whichever is available. Q621 2SD661-S or 2SC1815-GR Remember the matching pairs are: Q635/Q637 Sanken 2SA1215 -O / 2SC2921-O (suffix is the letter "O") Q631/Q633 couldn't find Sanken 2SA1667/2SC4381 suffix data. Q627/Q629 On-semi/Fairchild...
  11. dorke

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

    About Q625, Don't un-solder anything. I see you have Q623 with an "S" suffix, what suffix is there on Q624? Q631/Q633 look like a "modified" Q , more then anything else. Same on the other channel Q632/Q634 ?
  12. dorke

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

    The photo isn't clear enough. If possible, a better pic please. Most TRs have the logo of Mitsubishi (the triangle) Q631/Q633 suffix could be Q or R,very hard to tell. Q625 could have a "T" suffix,verify with the other channel Tr Q626. In general,another better way to get the suffix is to...
  13. dorke

    Having trouble identifying a diode needed for a repair.

    You can repair the traces with a simple wire,no need for trace material. By "What is written on the switch" I meant the "functionality label"-what is it switching. This equipment is probably operated by a 12V or 24V truck battery,isn't it? The voltage suppressor diode is probably protection...
  14. dorke

    Having trouble identifying a diode needed for a repair.

    You have 2 wires(red in the drawing) destroyed by over current (a short?)in the 2 diodes. The diodes look to be connected in a rectification arrangement. The 3rd diode 1N6282AG(yellow) is a 30V transient suppressor . The fact it is cracked means high voltage(>41V) was probably connected or...
  15. dorke

    Cheapest way to get data from multiple(100s) of sensors?

    A DVM is a Digital Volt Meter, the basic essential measurement tool,nothing can be debugged without it. You can get a basic, poor quality, entry level one for about 3$. Like the DT830,it should be fine for you. Don't know or use "Fritzing". I didn't check the 74HC595 connections. You have to...
  16. dorke

    Having difficulty identifying this resistor

    Welcome to EP. Yor resistor is 022x0.01 = 0.22 ohm 1%
  17. dorke

    Cheapest way to get data from multiple(100s) of sensors?

    Yes, there is a major problem. Assuming the sensor notation is "D" for diode and "T" for transistor. You need to connect a wire from the junction of T+ and the 3.3K resistor to pin 13 of the CD4051 instead of the blue wire now connected. A DVM should be used to de-bug this circuit,do you have one?.
  18. dorke

    Having trouble identifying a diode needed for a repair.

    They could be 1N5404 rectifier diodes Are those "3 black thick wires" coming from a line transformer ?
  19. dorke

    A simple circuit help

    welcome to EP. Could you please post a photo of the ICs(what is written on them),and LEDs you have. Are you sure it is a 9V battery you should use? The 74xx ICs will operate from a 5v battery a 9V one will destroy them! Do you know how to translate a Boolean equation into a circuit consisting...
  20. dorke

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

    We need to look at the suffix letter of the Trs as well. If visible/readable on the bad device that would be fine, if not then look at the corresponding Tr in the bad channel. e.g the batwings D845 R ,B755 R the suffix letter here is (R). That letter in Japanese Trs determines the Hfe range...
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