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Oscilloscope UNAOHM G4020 = BECKMAN 9020

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    #16
    Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

    This is where the second scope would be good. Because we are getting sweep output from the back (but how good of a ramp output is it? Aha..need another scope.) the sweep generator is working as far as I can tell. This output is directly used for the X deflection through R6001 and R961.

    But you say you can move the X dot from left to right with the X pos potentiometer, so the X amplifier is working depending on T908. But one can't work without the other.

    Some observation is conflicting here. Well, unless if one of R6006 or R961 is broken, HG1 connector is broken, or the wire broke...
    Last edited by eccerr0r; 08-02-2018, 11:10 AM.

    Comment

      #17
      Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

      Originally posted by eccerr0r View Post
      This is where the second scope would be good. Because we are getting sweep output from the back (but how good of a ramp output is it? Aha..need another scope.) the sweep generator is working as far as I can tell. This output is directly used for the X deflection through R6001 and R961.

      But you say you can move the X dot from left to right with the X pos potentiometer, so the X amplifier is working depending on T908. But one can't work without the other.

      Some observation is conflicting here. Well, unless if one of R6006 or R961 is broken, HG1 connector is broken, or the wire broke...
      Thank you very much for your detail research.

      BEAM FINDER ok

      And the Y ... I can't see any vertical lines, only one dot.
      Vertical Final Amplifier is ok

      Any control before this blocks?


      " ... have you looked inside yet? ..."
      search for any ...


      Regards,

      Ruy

      Comment

        #18
        Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

        Show a photo of the insides to us, I picked out one wire from the schematic, perhaps we can find that wire in a picture for you to inspect, at least visually, if you don't have another scope to check it.

        But wait, you say vertical amplifier is OK, so if you feed in an AC to the vertical inputs, you should be able to see a vertical line, perhaps requiring the use of the beamfinder button. If you're not getting any vertical line with an AC input, then we have some strange dual failure that my be just a switch problem.
        Last edited by eccerr0r; 08-02-2018, 07:45 PM.

        Comment

          #19
          Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

          Originally posted by eccerr0r View Post
          Show a photo of the insides to us, I picked out one wire from the schematic, perhaps we can find that wire in a picture for you to inspect, at least visually, if you don't have another scope to check it.

          But wait, you say vertical amplifier is OK, so if you feed in an AC to the vertical inputs, you should be able to see a vertical line, perhaps requiring the use of the beamfinder button. If you're not getting any vertical line with an AC input, then we have some strange dual failure that my be just a switch problem.
          This is great ... Thanks.




          " ... say you can move the X dot from left to right with the X pos potentiometer, so the X amplifier is working ..."

          I can move CH 1 and Ch 2 dot up and down with the Y POS I, II potentiometer, I deduce
          "Vertical Final Amplifier is ok" ?


          " ... the use of the beamfinder button." Please explain.

          Regards,
          Ruy
          Last edited by neuron; 08-02-2018, 08:46 PM.

          Comment

            #20
            Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

            If you can move the Y pos pots and its respective dot can be moved up an down, it demonstrates quite a bit is working - multiplexer is working, and yes, the Y finals are working. Doesn't show much about the preamp condition.

            But what can you do with the X position, from the front panel, anything at all?

            If the trace that would have shown a vertical line off screen is brought to the center with beamfinder, then you would be able to see it with beamfinder depressed. It's just proof that the vertical input amplifiers are working too.

            Comment

              #21
              Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

              still waiting for picture upload.

              Comment

                #22
                Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

                Originally posted by eccerr0r View Post
                If you can move the Y pos pots and its respective dot can be moved up an down, it demonstrates quite a bit is working - multiplexer is working, and yes, the Y finals are working. Doesn't show much about the preamp condition.

                But what can you do with the X position, from the front panel, anything at all?

                If the trace that would have shown a vertical line off screen is brought to the center with beamfinder, then you would be able to see it with beamfinder depressed. It's just proof that the vertical input amplifiers are working too.


                " ... say you can move the X dot from left to right with the X pos potentiometer, so the X amplifier is working ..."



                With the CAL signal?
                I will test

                " ... still waiting for picture upload."

                working

                Best Regards,
                Ruy

                Comment

                  #23
                  Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

                  Doesn't matter what the Y source is, you could set your input attenuators to 10mV and touch your fingers using the highly prevalent line frequency noise that should be everywhere if you're in an urban or suburban environment.

                  Depending on the edge rate of the calibrator output vs you time/division, you may just get two dots...

                  Comment

                    #24
                    Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

                    Originally posted by eccerr0r View Post
                    Doesn't matter what the Y source is, you could set your input attenuators to 10mV and touch your fingers using the highly prevalent line frequency noise that should be everywhere if you're in an urban or suburban environment.

                    Depending on the edge rate of the calibrator output vs you time/division, you may just get two dots...
                    Thank.
                    Attached Files

                    Comment

                      #25
                      Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

                      In pag. 54 R410 +24V EXT S601

                      In page 55 HG1 GB S601
                      to 56 SWEEP SIGNAL T703

                      More JPG to analyse

                      Regards,
                      Ruy
                      Attached Files

                      Comment

                        #26
                        Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

                        Okay, wait. Now I see horizontal lines. This means that the horizontal amps and oscillator is trying to do something. What are the settings and input that generated this picture? This is why if it's possible I'd like to see the picture of the scope's screen output AND the settings of the scope at the same time, with pictures of probes hooked up to the inputs. This would help rule out communications issues when typing in descriptions of what you see.

                        Now what I don't know is if the vertical amplifiers are working since we are seeing horizontal lines.

                        After reporting what are the settings and input that described how you got those horizontal lines shown, can you move those lines left/right and up/down, all the way, with the X-pos and Y-pos potentiometers. Also what happens when you add in a sinusoidal Y-input from the attenuators if you aren't already (set input to say 10mV and touch the pin of the probe).
                        Then take a picture if it changes from the shown picture.

                        Also while you're at it: measure all power supplies except the CRT second anode and CRT cathode voltage. You may have a weak power source that would explain both X and Y issues if you indeed have both issues. I ask not to measure the CRT second anode and cathode voltages because these are likely several thousand volts, and most people don't have the equipment to safely measure these.

                        (unrelated to the scope, just beef about cameras:
                        Also another thing I wish people had the capability of doing: using a tripod and making long exposure shots of the screen. It's an advanced photography technique that many cell phones can't do - in the realm of requiring DSLRs or at least better software/hardware that allows turning down the camera's sense amplifiers...)
                        Last edited by eccerr0r; 08-04-2018, 07:04 PM.

                        Comment

                          #27
                          Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

                          Originally posted by eccerr0r View Post
                          Okay, wait. Now I see horizontal lines. This means that the horizontal amps and oscillator is trying to do something. What are the settings and input that generated this picture? This is why if it's possible I'd like to see the picture of the scope's screen output AND the settings of the scope at the same time, with pictures of probes hooked up to the inputs. This would help rule out communications issues when typing in descriptions of what you see.

                          Now what I don't know is if the vertical amplifiers are working since we are seeing horizontal lines.

                          After reporting what are the settings and input that described how you got those horizontal lines shown, can you move those lines left/right and up/down, all the way, with the X-pos and Y-pos potentiometers. Also what happens when you add in a sinusoidal Y-input from the attenuators if you aren't already (set input to say 10mV and touch the pin of the probe).
                          Then take a picture if it changes from the shown picture.

                          Also while you're at it: measure all power supplies except the CRT second anode and CRT cathode voltage. You may have a weak power source that would explain both X and Y issues if you indeed have both issues. I ask not to measure the CRT second anode and cathode voltages because these are likely several thousand volts, and most people don't have the equipment to safely measure these.

                          (unrelated to the scope, just beef about cameras:
                          Also another thing I wish people had the capability of doing: using a tripod and making long exposure shots of the screen. It's an advanced photography technique that many cell phones can't do - in the realm of requiring DSLRs or at least better software/hardware that allows turning down the camera's sense amplifiers...)

                          The settings:

                          https://www.badcaps.net/forum/showpo...2&postcount=11

                          https://www.badcaps.net/forum/showpo...8&postcount=14

                          TIME / DIV is 5us, 10us - trace ( tail ) with 1 cm.


                          " ... can you move those lines left/right and up/down, all the way, with the X-pos and Y-pos potentiometers. ..."

                          YESSSSSSSSSSSSSSSSSSSSSSS
                          I explained in previous post

                          "... CRT second anode and cathode voltages because these are likely several thousand volts ..."

                          -1867 V
                          1,9KV


                          Best Regards,
                          Ruy

                          Comment

                            #28
                            Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

                            Which settings go with which picture, and you have NO external input?

                            So you're saying "tall" when the picture shows "wide" ... This is why I'm confused!
                            Last edited by eccerr0r; 08-04-2018, 08:06 PM.

                            Comment

                              #29
                              Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

                              a good clean is an idea, there are solder balls and splats all over the underside of that board!!

                              Comment

                                #30
                                Re: Oscilloscope UNAOHM G4020 = BECKMAN 9020

                                This is dated 1988 so the electrolytic capacitors look pretty old. If there is AC hum, the ripple would make the trace/dot into a bar.

                                I would check the +140VDC rail, and filter cap C524 47uF 250V, used for both the CRT X (horiz) AND Y (vert) deflection amps, and is part of the +260V rail.
                                I would check the +260VDC rail, and filter cap C523 47uF 250V, used for the CRT X (horiz) deflection amps.

                                Comment

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