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  1. (*steve*)

    My brand new oscilloscope

    33V zener (green) looks like a good match to the higher Vf selenium rectifier: Practically speaking, the 27V zener (yellow) is probably the way I'll go. Any comments?
  2. (*steve*)

    My brand new oscilloscope

    Here is the graph of the replacement's Vf vs I curve: The curve in yellow is the replacement. Unfortunately all I could find was a 27V zener, not a 35V zener :-( The curve seems similar enough. What if I put a 13V and a 20V zener in series?
  3. (*steve*)

    maximize efficiency of a solar panel charging a Li-Ion battery

    Sorry, I thought I mentioned that in post #9.
  4. (*steve*)

    My brand new oscilloscope

    Here is the result of a test of the selenium rectifier: The two diodes are a little different in their characteristics. I have no way of knowing if this is due to the normal spread of Vf or if one of the devices has a fault. I'm going with the top graph because if you're talking about...
  5. (*steve*)

    My brand new oscilloscope

    Some of these call capacitors are pretty old. This one will be having its 50th birthday next year.
  6. (*steve*)

    Old philips pm3310

    There is nothing obviously burnt in the power supply. That doesn't mean it's not a power supply fault, but it means we may need to look further. The fact that the power supply seems to start up then shut down may indicate that either it is overloaded or is detecting something incorrect with...
  7. (*steve*)

    Old philips pm3310

    Take some well lit (not flash) photos and post them. A picture may give us enough information to suggest where to look. I posted a thread a while back about fixing the power supply in my Phillips scope. I'm my case the problem was pretty obvious though.
  8. (*steve*)

    Lab Volt Model 790A will not power up

    Yes, electrolytic capacitors require you place then in the circuit the correct way around. Before you remove existing electrolytic capacitors make very sure you record which way around the old ones were. If the is no polarity marking, the capacitors may not be electrolytic. It is also...
  9. (*steve*)

    Anyone know of any microcontrollers which can communicate via radio?

    Truly an example of lack of mastery. @CircuitMaster, I'm afraid I'm going to continue to call you out for the simplistic (and frequently false) statements you make. Please take to heart my suggestion that you try to make sure that your posts add information, not subtract from it.
  10. (*steve*)

    TI-84 Plus Calculator Bit the Dust

    Are you sure the batteries didn't cause additional problems? Can you post some pictures of the board. Congrats on finding the right screwdriver. We've been waiting for you to return :-)
  11. (*steve*)

    Charge time for lithium batteries

    Using the correct charger, the batteries are charged when the charger indicates they are. The time depends on the amount of charge remaining before you start to charge them, the capacity of the batteries, the charging efficiency, and the power the charger can put back into the battery (i.e. the...
  12. (*steve*)

    best wire for soldering, and do components have to breathe?

    The best type of insulation to be used when soldering is NO insulation. You must remove it in order to solder the wire. Components do not breathe. Some require airflow (for example airflow sensors or gas detectors) and others require cooling which (on terrestrial applications at least...
  13. (*steve*)

    Change in site ownership

    Are you having problems accessing the site?
  14. (*steve*)

    then what does jp1 and jp2 mean here?

    Look here.
  15. (*steve*)

    then what does jp1 and jp2 mean here?

    It could be. It's definitely NOT for swapping the transmit/receive pins (and that only works for 3 wire connections - that this is not). It's difficult to tell where the jumpers connect to, but I can see where they don't connect to :-)
  16. (*steve*)

    My brand new oscilloscope

    Oh it's a pig. I might have to remove the CRT and just try to get at the connections from the back of the board. Unfortunately there's a transformer partially in the way and all the stuff behind the various controls that I need to work around. And lots of wires too short to allow much...
  17. (*steve*)

    then what does jp1 and jp2 mean here?

    It means Jumper. Pull those blue things off and you'll find 2 pins. Those blue blocks contain a bit of metal that joins the two pins together. Typically it's for setting an option, but you'd have to look up the documentation to see what these are for. It *might* swap the transmit and receive...
  18. (*steve*)

    G & E Bradley CT471C

    If you havea schematic and a good description of what is going on, then we may be able to help. With neither of these (especially without any description of the fault) then there is no way to say if we can help.
  19. (*steve*)

    My brand new oscilloscope

    I did two things today. The first was construct a constant current circuit suitable for up to 0.5mA and a couple of hundred volts. Here it is: I'm testing it here with an 11V zener. And it works like a charm :-) The two 2k2 resistors in parallel give a current very close to 0.5mA. I...
  20. (*steve*)

    Change in site ownership

    Also... recent activity, posting history, etc uses unreasonably large fonts.
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