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  1. (*steve*)

    My brand new oscilloscope

    Here is the cal signal. The trigger seems to be a bit "dicky". And the cal signal isn't 500mV, it's closer to 50mV
  2. (*steve*)

    My brand new oscilloscope

    Doh! I guess I don't. Do you know how long I spent looking for the calibration oscillator in the circuit diagram? Maybe I should run through the calibration procedure and see if everything can be brought into spec. Or maybe I should try to find what caused the horizontal width to reduce...
  3. (*steve*)

    My brand new oscilloscope

    Woo hoo! And now the focus works correctly too. Need to fix the cal output next.
  4. (*steve*)

    My brand new oscilloscope

    I knew these would come in handy one day. What? me? a magpie?
  5. (*steve*)

    My brand new oscilloscope

    The first step is to check the power supply. If it's doing something wrong then lots of stuff can be affected. Lots of high voltages, and my meter read up to 1000VAC and 500VDC :-( Not to worry, not everything needs to be measured with respect to ground. But placing the meter's ground lead...
  6. (*steve*)

    Buck Converter with PİC16F877A

    The stuff with bat1 and bat3 doesn't make any sense to me. The batteries seen to be rendered ineffectual by R3 that will limit the voltage to about 1/3V. For a high side switch, why are you not using a P channel MOSFET?
  7. (*steve*)

    My brand new oscilloscope

    For anyone repairing a scope, this document might come in handy. It's from Tektronix, but it's somewhat agnoistic to the brand or type of scope you have. Other than some particular Tektronix quirks, much of it applies to any analog scope.
  8. (*steve*)

    My brand new oscilloscope

    Partial success! The vertical position doesn't change with the vertical gain any more. The width of the trace doesn't vary with time. But the "brilliance" is fixed, and I can't get a better focus than shown (but I can do a lot worse). Also the cal signal is 50Hz, which is line frequency...
  9. (*steve*)

    My brand new oscilloscope

    I'll go with that being my meaning :-) The front cover us back on... Did I mention that a previous owner has disconnected the earth? At least they made it obvious. I know what this means, and I'll be careful :-)
  10. (*steve*)

    My brand new oscilloscope

    There's not a lot of room to replace those lamps with LEDs, so I might make a strip of surface mount LEDs... later. Another issue is that after reading the in-circuit values of many of these carbon composition resistors, about half read higher than the rated value. The worst I found was a 330K...
  11. (*steve*)

    Small SMD Fell Off Motherboard

    check out this: and this: and finally this:
  12. (*steve*)

    LED help

    Yeah (maybe), but the 1W LEDs in the video aren't on a star. CREE has a very useful document discussing thermal management. This doesn't give the relationship between die temperature and lifetime, but points to another document that gives similar information for each of many, many, many...
  13. (*steve*)

    My brand new oscilloscope

    Those are GP02-40-E3/54's. They're somewhat higher rated than 1N4007's :-) Those replacement rectifiers are probably OK up to 8kV -- The originals were rated at 3.5kV. I used 2 diodes because: Selenium rectifiers are more tolerant of transient high reverse voltage than silicon diodes The...
  14. (*steve*)

    Analog guitar amp with digital meter

    No, but the vocalists and other musicians (mostly guitarists) who have expressed interest in my tube preamp seem to think the same way as you. I'm happy to sell them what they want. I was simply congratulating you for figuring a way to extract more of their money. Unfortunately the musicians...
  15. (*steve*)

    My brand new oscilloscope

    Always one more step... Here is a failed graticule illumination lamp. I'm planning to replace it with a LED. Currently there is a 100Ω pot across a 13.5VAC winding with the wiper connected to two small 14V globes. I'm planning to half wave rectify the AC from the pot, filter it and use...
  16. (*steve*)

    Amateur (Ham) Radio and RC (Radio Controlled) Flight

    Sure, ATC would love that. So what classes of airspace do you fly your quadcopter in, and which ATC is responsible for it? How do you ensure that other aircraft can see and avoid you?
  17. (*steve*)

    Analog guitar amp with digital meter

    No, I'm just suggesting how these things are typically used. If you have a resetable device there is always a question as to whether it has been inadvertently (or not) reset, and it removes the capability of having a series of service intervals (replace output tubes every 200 hours, phase...
  18. (*steve*)

    Is it wrong to leave a transformer plugged in ??

    My advice would be to install a separate switch to remove mains power from the power supply. If it is already plugged into a wall outlet then that is sufficient. Even if you don't turn it on and off at this switch, you do have the capability of isolating the power supply if you need to...
  19. (*steve*)

    Is it wrong to leave a transformer plugged in ??

    I find it humorous that you say that, then indicate you have the same concerns. Not too many of us will think "Oh, he's in Thailand, I'll give him worse advice than I would to someone in another country."
  20. (*steve*)

    Analog guitar amp with digital meter

    Note the number of hours currently on the meter. Calculate the number of hours until the next service interval. Add these numbers together. Get a small piece of clean white paper and a non-erasable pen. Write on the paper "service at xxxx hours", where xxxx is the number calculated in step 3...
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