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A hard to resist problem

Discussion in 'General Electronics Chat' started by Justin Verrall, Dec 22, 2015.

  1. Justin Verrall

    Justin Verrall Member

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    Oh yeah I do have the tube. I took it out so I didn't break it
     
  2. throbscottle

    throbscottle Well-Known Member

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    Since you're fairly new to electronics, FYI I think KISS probably means the + and - inputs of the op-amps, not their power supply pins!
     
  3. Justin Verrall

    Justin Verrall Member

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    Hey I just tried buying the scope and they don't ship to NZ. I can't contact the seller either. What should I do?[​IMG]
     
  4. dave

    Dave New Member

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  5. Gasboss775

    Gasboss775 Member

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    Has money changed hands. If so contact eBay customer service. Why can't you contact the seller?
     
  6. Justin Verrall

    Justin Verrall Member

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    No money has luckily and they opted to not be able to be contacted.
     
  7. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    I'm lost. Cowboybob has been ranting about his tiny scope.

    ebay's "money back guarantee" works. I used it 1x with absolutely no issues whatsoever.

    I just got an instantaneous refund when I contacted a seller that a laptop keyboard wasn't as pictured. I got to keep the keyboards. I swear, the problem was resolved with the seller in like 15 minutes.
     
  8. Justin Verrall

    Justin Verrall Member

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    No money has been payed luckily and they opted to not be able to be contacted.
     
  9. spec

    spec Well-Known Member Most Helpful Member

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  10. Justin Verrall

    Justin Verrall Member

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  11. spec

    spec Well-Known Member Most Helpful Member

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    Don't worry it will help us to find out what is wrong. Your first port of call is to check all the supply lines. It is quite common for the reservoir capacitors to fail. That can take out the rectifiers. If there are any LEDs used for biasing, check those too. The potentiometers are low quality and tend to wear out too.
     
  12. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    spec: nice find

    What you really need now is a constant signal source. e.g. 1 Khz.

    You can use your meter in relative mode (db) to help isolate the stage.

    The difference of the inverting and non-inverting inputs of the OP amps is a place to start. Measured in normal mode and fail mode.
    Surely you can do that. Without looking at the schematic, let's say the difference should be close to zero.
     
  13. throbscottle

    throbscottle Well-Known Member

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    It's not hard to build an un-calibrated 'scope if you feel like the challenge. There was a very good book from Babini "how to build your own solid state oscilloscope". In the '80's I built it, worked well, very out of date now, (getting out of date even then) the tube must be antique! But the principle stands all the same. I built a very crude digital one too, with a 10 x 10 led matrix display, all hand soldered out of square 5mm LED's. It used a clock/counter as the timebase and some kind of bargraph controller (I think I designed my own because I didn't realise bargraph chips existed!) as the vertical control. Worked ok but not very usable.
    If you can source the materials, building a simple 'scope is an educational project in lots of ways, and you end up with a useful piece of equipment at the end of it.
     
  14. throbscottle

    throbscottle Well-Known Member

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    I'm intrigued Justin - what 'scope did you order? I don't see a model mentioned earlier in the thread?
    You could check out alibaba and banggood too.
     
  15. Justin Verrall

    Justin Verrall Member

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    I didn't order a scope I was trying to order a PSU
     
  16. throbscottle

    throbscottle Well-Known Member

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    Bit of a typo there, then :angelic:
     
  17. spec

    spec Well-Known Member Most Helpful Member

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    That caught me out too :)
     
  18. Justin Verrall

    Justin Verrall Member

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    Got me there ;) I've never been good at spelling.
     
  19. spec

    spec Well-Known Member Most Helpful Member

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    Big mistakes are no mistakes. Little mistakes are big mistakes. :cool:
     
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