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Sciaky model C.R.O.I. what is it?

Discussion in 'General Electronics Discussion' started by (*steve*), Jan 28, 2020.

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  1. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Here's my latest find. It looked interesting, but I don't know anything about it.

    IMG_20200128_200824_compress61.jpg

    It's 15.5 x 11.5 cm (x 11.5cm deep).

    Probably made in Australia. Capacitors are a mix of British and Australian made. Contains 2 x 6AM6 tubes and the display tube (so far unidentified). No obvious rectifier...

    Has someone snapped off banana plugs in the sockets?

    What the heck does it do?
     
    davenn likes this.
  2. shrtrnd

    shrtrnd

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    Jan 15, 2010
    Besides take-up room on your workbench?
    I don't know, never heard of the company before.
     
  3. Minder

    Minder

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    I used to work on Sciaky resistance welders, they used a Dekatron tube for timing, looks like one on the unit.
    Not sure what this unit did though?
    M.
     
  4. bertus

    bertus Moderator

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    Hello,

    It looks like an oscilloscope.
    The first oscilloscopes did not have a trigger function and had a free running oscillator as timebase.
    The trick was to adjust the frequency knob to have a steady picture on screen.

    From the wiki:

    Synchronized sweep
    [​IMG]
    Oscilloscope with synchronized sweep. "HOR. SELECTOR" sets horizontal frequency range (the capacitor); "FREQ. VERNIER" adjusts the free-running frequency; "SYNC. AMPLITUDE" sets the gain to the comparator.

    Early oscilloscopes used a synchronized sawtooth waveform generator to provide the time axis. The sawtooth would be made by charging a capacitor with a relatively constant current; that would create a rising voltage. The rising voltage would be fed to the horizontal deflection plates to create the sweep. The rising voltage would also be fed to a comparator; when the capacitor reached a certain level, the capacitor would be discharged, the trace would return to the left, and the capacitor (and the sweep) would start another traverse. The operator would adjust the charging current so the sawtooth generator would have a slightly longer period than a multiple of the vertical axis signal. For example, when looking at a 1 kHz sinewave (1 ms period), the operator might adjust the horizontal frequency to a little bit more than 5 ms. When the input signal was absent, the sweep would free run at that frequency.

    If the input signal were present, the resulting display would not be stable at the horizontal sweep's free-running frequency because it was not a submultiple of the input (vertical axis) signal. To fix that, the sweep generator would be synchronized by adding a scaled version of the input the signal to the sweep generator's comparator. The added signal would cause the comparator to trip a little earlier and thus synchronize it to the input signal. The operator could adjust the synch level; for some designs, the operator could choose the polarity.[13] The sweep generator would turn off (known as blanking) the beam during retrace.[14]

    The resulting horizontal sweep speed was uncalibrated because the sweep rate was adjusted by changing slope of the sawtooth generator. The time per division on the display depended upon the sweep's free-running frequency and a horizontal gain control.

    A synchronized sweep oscilloscope could not display a non-periodic signal because it could not synchronize the sweep generator to that signal. Horizontal circuits were often AC-coupled

    https://en.wikipedia.org/wiki/Oscilloscope_history

    Bertus
     
    Last edited: Jan 28, 2020
    hevans1944 likes this.
  5. Minder

    Minder

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    Looks like Sciaky is still in business https://www.sciaky.com/
    It was back in 1962 when I worked in their machines.
    Drop them an email, they may shed some light on it.
    M.
     
  6. Externet

    Externet

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    C.R.O.I ----guessing ?----> Cathode ray oscilloscope interface ?
     
  7. bertus

    bertus Moderator

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  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    The tube is shielded, but that CRT looks to be in the ballpark for size.

    When I first saw a picture of this, I assumed the dimensions we're about twice what they turned out to be. Even then, I thought it was a tiny display.

    When I pulled it out of the packaging I was quite surprised.
     
  9. hevans1944

    hevans1944 Hop - AC8NS

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    My first oscilloscope was an EICO 460K, built from a kit. It had a non-triggered, reoccurring, synchronized sweep like @bertus described in post #4, but with what I thought was a huge 4" CRT. It was pretty good for TV servicing, but I didn't find out until I went to Air Force tech school in 1963 that REAL o'scopes had triggered sweeps and calibrated time bases. And all the good ones were made by Tektronix, but at prices ordinary people could not afford. It was many years later that I finally was able to purchase a used Tektronix o'scope at a Dayton Hamvention for $300 cash money.

    Your o'scope looks like it might have a one-inch or maybe a two-inch CRT. IIRC, this size was popular with the first RADAR PPI (Plan Position Indicator) displays used during WWII. A lot of those CRTs became available on the surplus market after the war, repurposed for use as a "poor man's oscilloscope." Looks like a few wound up in commercial oscilloscope products too, like the one you have. I like the "wings" motif surrounding the CRT. It adds a bit of class. Excellent find Steve.
     
    (*steve*) likes this.
  10. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Yeah, the crt is about 1 inch in diameter.
     
  11. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Well, I'm feeling good enough to take a look at this unit. I've managed to source replacement capacitors.

    Here's what it looks like inside:

    Looking in the right side, there's quite a few paper capacitors and a 6AM6 tube (it's a "British made" Mullard tube). Behind that tube is the crt in a metal shield.

    IMG_20200328_082654_compress6.jpg

    The left hand side of the unit shows the 6AM6 tube ("Made in Great Britain" Miniwatt) and a couple more capacitors. Keen eye may be able to see the broken lead (dis) connected to the red input terminal.

    IMG_20200328_082716_compress9.jpg

    And the back. There is the mains lead, and it seems well secured. You've also got the valve sockets, a view of the transformer that's been hiding behind stuff in the other photos, and some large capacitors. Notably, you can see the capacitor on the lower right is "Made in Aust."

    IMG_20200328_082626_compress89.jpg

    I'm keen to power it up and see what happens...
     
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  12. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    No smoke!

    The filaments glow...

    IMG_20200328_092123_compress84.jpg

    And after some adjustments to the brightness and position...

    IMG_20200328_093003_compress47.jpg

    Woo Hoo! (Actually, it's a little disappointing that it works ;-) )

    The trace appears shifted to the right, and the vertical position seems to move the trace diagonally.

    The voltages inside are pretty moderate. The highest voltage measured was around 400V, and it bleeds of pretty quickly.

    So... Replace those capacitors!
     
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  13. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Oh, I'm almost 100% sure that there are banana plugs snapped off in those sockets, and the red one is clearly not original.

    Should I try to fix them? Replace them with normal banana sockets? Replace them with "safety" banana sockets? Install a BNC socket?

    What do you think?
     
  14. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Before:

    IMG_20200328_082626_compress89.jpg

    After:

    IMG_20200328_103148_compress44.jpg

    They've shrunk!
     
  15. Minder

    Minder

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    That would be a 'Valve' then!:p:D
    Max.
     
  16. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Well, it looked like there were banana plugs snapped off, but it turns out that insects had made their home in them! Sure looked like metal!

    It certainly would. I am just catering to all the members here that speak a language that's almost, but not quite, English.

    Quite a few of the capacitors are really hard to get at. So it's time to take this thing apart!

    IMG_20200328_111159_compress59.jpg

    Wiggling the CRT made the fancy bezel around it fall off. This out it was just glued in place. Then I removed the bakelite knobs

    IMG_20200328_113128_compress17.jpg

    Taking off the nuts holding the pots and switches almost allows the front to come off, but that red terminal post is a problem.

    IMG_20200328_113923_compress52.jpg

    Removing the red jack allows the removal of the front panel. This reveals couple of bolts holding the chassis together.

    IMG_20200328_114000_compress81.jpg

    And removing them gives me better access to everything.

    IMG_20200328_114746_compress1.jpg

    Removing the loctal CRT gives me even better access.

    IMG_20200328_120034_compress19.jpg

    Here are some of the replaced caps on the left hand side

    IMG_20200328_131303_compress82.jpg

    And the right hand side.

    Now I need to find some better terminal posts if I can.
     
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  17. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    I forgot to show you the CRT.

    IMG_20200328_142139_compress83.jpg

    And I connected up a signal generator to see how it behaved. First at 300Hz

    IMG_20200328_152352_compress37.jpg
    Sine

    IMG_20200328_152407_compress98.jpg
    Square

    IMG_20200328_152412_compress65.jpg
    Triangle

    Now 3kHz
    IMG_20200328_152641_compress18.jpg
    Sine

    IMG_20200328_152702_compress80.jpg
    Square

    On the fast timebase and the 5V range the 3db points are approximately 100Hz to 1MHz. The 3db points don't seem to change with the timebase, but they do with the voltage range. It's a lot less on the 10V range, but seems to increase in the higher voltage ranges.
     
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  18. bertus

    bertus Moderator

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  19. Minder

    Minder

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    As Sciaky is/was a specialized machine manuf., I suspect that may have been a piece of equipment used in the process of setting up or calibrating one of these M/C.s ;)
    M.
     
  20. hevans1944

    hevans1944 Hop - AC8NS

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    I think you should try to replace those "insect hotels" with common red and black, chassis-mount, banana jacks, NOT "safety" banana sockets, NOT BNC socket(s), and NOT five-way binding posts. Also avoid the temptation to replace the valves with transistors of any species, including any included as a part of an integrated circuit. IMHO it's okay to replace the knobs with new ones, even aluminum knobs, since you probably won't find bakelite equivalents to the originals. I think the whole point of "restorations" is to try to make them look and function as much like the original as possible without "cheating" by installing "modern" components. For example, you could replace the valves with op-amps and the CRT with a LCD display, masked to appear round, but that would be cheating. Replacing suspect capacitors (anything manufactured in the 20th Century) with modern equivalents is okay.

    Great find, Steve, and looks like a great re-cap job too. Hook this up to an audio amplifier and a microphone to catch the attention of, and to amaze, visitors to your domain.

    Look, Ma! I'm on TV! Er, sorta...

    Seriously, if you can find some way to amplitude modulate the cathode of that itty bitty CRT with analog video, this would make a really good "fit" to an NTSC lip-stick camera. Just add a few external electronic circuits, such as vertical and horizontal sweep and a sync circuit with horizontal and vertical blanking. Also add a VHS recorder for some real "steam punk" nostalgia.:cool:
     
    Last edited: Mar 30, 2020
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