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  1. dorke

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

    Well, Q709 is also wrong Vb=Vc ? Take the time to measure the above voltages (Q707 up to Q710) in the same conditions: 1.same GND reference for the (-)probe. 2.Volume at minimum.
  2. dorke

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

    Voltages are a bit of. and Q707 is wrong (it has 2 pins tied together) Could you please re- check all with (volume at minimum) and add Q709 as well.
  3. dorke

    simple radio amplification

    Read it like 14:30 ? ;)
  4. dorke

    Wire wrap circuit

    @colum, What kind of circuits are you going to build? Analog,Digital? What kind of technology and speed/frequency? What kind of packages are you planning to use?
  5. dorke

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

    Welcome back, Please measure the voltages on Q708 and Q710 relative to GND. Can you quantify "pretty hot" in degrees ?
  6. dorke

    Multisim - How do I find the Resonant Frequency (FR) on an LRC circuit?

    Hop, In Multisim the number of points chosen for calculations aren't necessarily the same as the points displayed. There is an option to chose the points displayed and lines connecting them. Absolutely ,a linear vertical mode would dramatize changes of the plot, although for filters the...
  7. dorke

    Multisim - How do I find the Resonant Frequency (FR) on an LRC circuit?

    A few things: 1.You should learn how to modify the default labels to have meaningful names ,like so: 2.Your simulation is fine,try this setting and display it in "full screen size". 3.This is the result:
  8. dorke

    Multisim - How do I find the Resonant Frequency (FR) on an LRC circuit?

    It is called "AC Analysis frequency response". Here you have a How to Video
  9. dorke

    Multisim - How do I find the Resonant Frequency (FR) on an LRC circuit?

    The method is correct but your answer isn't. You entered the wrong numbers for C=0.01e-6
  10. dorke

    How to remove solder from plated-through holes?

    And,don't forget to have your pants on...;)
  11. dorke

    How to remove solder from plated-through holes?

    For DIL packages 0.1"(2.54mm) pin spacing ,0.5mm is actually the width of the leg itself. The hole diameter is about 0.7mm. We have these Dinosaurs ICs for 50+ years,not a problem dealing with them. In terms of nowadays PCB/device sizes, it is indeed considered very large. via drill diameters...
  12. dorke

    How to remove solder from plated-through holes?

    @Alec_t, Sounds like you are doing things the wrong way! 1. A DIL chip doesn't have small holes ,they are large ,very large! 2. A 25W, and obviously a 15W iron are way too small for the job! 3. Never use a hand pump sucker it will most likely cause damage! 4. You need good quality iron...
  13. dorke

    Help me to understand this circuit

    Well, The diodes D2 and D3 are in parallel,so they would drop the voltage only by a single Vf . That Vf would depend on the specific diode and the current through it. You raise some good questions. Sometimes it is hard to get into the mind of a "designer" without knowing is...
  14. dorke

    LED burns when oscilloscope is connected to it

    Well, using a "standard mains operated non-isolated " scop to measure Mains isn't the way to go. There are several ways to by-pass this problem: 1. You can use a dedicated "differential isolated probe",expansive. 2. You can use a hand held scope (battery powered hence is isolated),very...
  15. dorke

    Wattage on things

    Let me add: In case the 1000W is the rated output power of the motor. What is the efficiency of the motor?
  16. dorke

    Voltage on a white LED.

    You shouldn't be surprised at all. The game when driving LEDs is the relations you get between current-Lumen-efficiency . Look at the graph(a high current LED): You get more Lumens as the current is increased(Red),but the efficiency drops(Blue). A designer needs to find the "sweet-spot" for his...
  17. dorke

    LED burns when oscilloscope is connected to it

    Most scopes(the vast majority) are not isolated. The GND of the input channel and probe are connected to chassis GND. It doesn't matter at all what the resistance of the prob is. As bob said the only thing to connect the prob to is GND in the tested circuit. One sure way to damage your scop...
  18. dorke

    Help me to understand this circuit

    I have removed part of my original post ,here it is again: Here is my view: The 2 Mosfets are shown to be enhancement mode : Q8- -N channel ,Q7- P channel. Q7 is a "high side switch" The voltage marked as " V_808 " will be present only after the voltage of the MP2307 output reached above...
  19. dorke

    General Purpose Programmer

    I don't now how things work in your area. Have you tried the "yellow pages" or any tech related similar thing, for "IC /memory Programming Services" ? These can be found worldwide even for hobbyers.
  20. dorke

    General Purpose Programmer

    Other ways to go about it: 1.Repair the ChipMaster 3000,contact the manufacture for that option, sometimes it is possible to get a working replacement till your unit is fixed. 2.Rent/lease a ChipMaster 3000,or any other suitable programmer,if you need it for a short period of time. Hope it...
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