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  1. (*steve*)

    An alternative to 74ls173's design ?

    In addition to that, the internal circuit you see in the datasheet is normally labelled an "equivalent circuit" because the actual circuit may be quite different. As a very simple example, an xor gate may be shown as having an equivalent circuit consisting of a number of gated which implement...
  2. (*steve*)

    Zero ohm resistors.

    A zero ohm resistor had the same form factor as any other resistor. Since resistors are common, there are no problems getting them automatically populated on boards. It makes sense to house a link in the same package. Zero ohm resistors can be used to provide a link for the purpose you'd use...
  3. (*steve*)

    Time reversal transformation

    At the risk of sounding like a broken record, look for a set of identities written pretty much exactly in the form I have given. You won't find f() around anything, but you will find exactly the same mathematical transformation applied. When you find that pair of identities, you can determine...
  4. (*steve*)

    Successful Stanford Research SR530 lock-in amplifier repair

    Here's a question for you guys... I'm starting to give dipped tantalum caps quite a bit of side-eye. I've had a number of failures in a row caused by them now. My initial thought was to replace them with low-ESR electrolytic caps, but I wonder if that's a good idea. My next thought is to...
  5. (*steve*)

    Successful Stanford Research SR530 lock-in amplifier repair

    My rationale in using what is essentially a synchronous motor is that the speed should be very tightly controlled by the frequency. At high enough speeds, the disc will act like a flywheel and reduce jitter. At low speeds I am looking at using pwm to drive the motor from what equates to a low...
  6. (*steve*)

    Tektronix TDS3054 data acquisition failure

    I think that red spike is a problem with the display or the connection to it. Although typically such defects go the whole way across the display, not just part way.
  7. (*steve*)

    Strange Chinese battery. Need help finding charger.

    Chances are the charger is a 25.9V current limited power supply and contact that the cell balancing is either internal to the battery module or the scooter. What does the charging port look like and how many wires connect to it? (Is it 2 wires only?)
  8. (*steve*)

    Time reversal transformation

    He is required to produce a "time reversed" signal for a sin or cos input signal. If the input is sin(x) then a time reversed signal is sin (--x). Three bug hint I'd that the circuit is permitted to have a time lag. The question is more about a basic understanding of the various trig...
  9. (*steve*)

    Tektronix TDS3054 data acquisition failure

    If it was just the display, I would expect that the functions which show the frequency, period, rise time, etc would still give valid results. But I get your point.
  10. (*steve*)

    Time reversal transformation

    Look on this page https://en.m.wikipedia.org/wiki/List_of_trigonometric_identities
  11. (*steve*)

    Time reversal transformation

    Try something else that will make the function obvious.
  12. (*steve*)

    Successful Stanford Research SR530 lock-in amplifier repair

    I'm planning to make a variable speed chopper as my next construction project. I've got a bldc motor because I can drive it at a known speed very easily. They are also designed to connect to a propeller, and the same mounting can be used to fix it to a chopper disc.
  13. (*steve*)

    Tektronix TDS3054 data acquisition failure

    Nothing I do (so far) in changing horizontal or vertical timebase settings, or zooming on a "captured" signal does anything that changes the red lines or even causes the patterns on the display to change how one might expect given the changes. I have not seen the horizontal spacing or position...
  14. (*steve*)

    Tektronix TDS3054 data acquisition failure

    Another thing that strikes me is that it is entirely possible that even though the DC rails checked out as having the correct voltage, a failed capacitor could make one or more rails noisy enough to affect the operation of something critical in the signal acquisition path. I'll check that too.
  15. (*steve*)

    Tektronix TDS3054 data acquisition failure

    I think the odds are pretty good. As in the previous repair, the fix may turn out to be simple and cheap, but finding it takes quite a while. The cost of time is generally what makes these things BER. However, the lack of schematics can mean that it's doubly difficult to know where to look...
  16. (*steve*)

    Tektronix TDS3054 data acquisition failure

    Yeah, I've seen that before. This unit is very new compared to that one. The front panel looks similar, but the box is probably only 1/5th the depth. The 3054 has the form factor of most modern digital scopes. I've done some prodding with a wooden stick, and nothing much happened. I've used...
  17. (*steve*)

    Tektronix TDS3054 data acquisition failure

    Look what I've been asked to fix now: There's a few teardowns on YouTube (Dave Jones tried to fix a fault on one of these). Bugger all documentation, and only a few voltages C/- Dave, so I'm not hopeful. Everything after the data acquisition seems ok (not sure if that includes the memory)...
  18. (*steve*)

    Electronics Mortuary

    Do you really think this is beyond economic repair?
  19. (*steve*)

    Successful Stanford Research SR530 lock-in amplifier repair

    Whoever designed the fastenings for that shield either had incredibly small fingers or a very evil sense of humour.
  20. (*steve*)

    Successful Stanford Research SR530 lock-in amplifier repair

    Woo hoo! Here it is working. My signal generator's sync is apparently 90 degrees out of phase with the signal. The signal is just under 1mV at 48.7kHz. It's not completely obvious, but the max sensitivity is 100nV full scale, but you can then do a X10 on that too get 10nV The current...
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