Hp Mx70

Collapse
X
Collapse
 
  • Page of 1
  • Time
  • Show
Clear All
new posts
Previous template Next
  • Gianni
    Badcaps Veteran
    • Jul 2008
    • 681
    • Italy
    #1

    Hp Mx70

    Yesterday I repaired a 17" CRT HP MX70.

    The problem appeared suddenly after some years of good work: moving the monitor or just knocking on it caused black screen, the image disappeared.
    Sometimes after turn on the screen remained black even if the video signal was present.
    The PS had no problem, the green Led was always on.
    After resoldering almost everything the problem was solved.

    I made this post because when I was cleaning up the PCB, I noticed a big yellow cap: CapXon 3.3uF 50V.
    I had no time to investigate where it was connected, so I would like to ask if someone here knows why it is so large and tall.
    Usually caps in the range of 1uF~47uF 50V have a diameter of 5mm~6.3mm, so I don't understand why this one is so large.

    TIA
    Gianni
    Attached Files
    "In the confrontation between the stream and the rock, the stream always wins...Not through strength, but through persistence."
    H. J. Brown
    Tags: None
    • Wizard
      Badcaps Legend
      • Mar 2008
      • 2296
      #2
      Re: Hp Mx70

      BiPolar capacitors have no polarity marking (noticed that?) and is MUCH much bulkier.

      It is used in the pincushion circuit in series with a pincushion coil (excited by PWM (there's is a FET on big heatsink near by. The small heatsink with another FET is for the horizontal scan S-cap (row of red poly caps and few more un-heatsinked FETs as well. This bi-polar cap is to "electrically" break this circuit into isolated circuits, bec one is working at low voltage while other side is about several higher voltages from horizontal circuit (within the capacitor's voltage ratings).

      Reason is the construction of capacitor is made of 2 capacitors in series with polaries facing each other as a unit.

      Better monitors doesn't use this cap, instead it uses a transformer.

      Cheers, Wizard
      Last edited by Wizard; 12-06-2008, 05:41 PM.

        Comment

        • Krankshaft
          Badcaps Legend
          • Jan 2007
          • 2328
          • USA
          #3
          Re: Hp Mx70

          Wizard beat me to it. That cap is a bipolar.

          The Toshiba (citizen chassis) with the vertical cap problem you helped me on had a bipolar like that too so thats how I know .

          Ahh no SMT components my dream board .

          On a related note does anyone know why CRT monitor neck boards need all of that shielding when TV CRTs don't?
          Elements of the past and the future combining to make something not quite as good as either.

            Comment

            • Gianni
              Badcaps Veteran
              • Jul 2008
              • 681
              • Italy
              #4
              Re: Hp Mx70

              @ Wizard: thank you very much for your explanation. I didn't notice the missing negative sign on the cap.

              @ Krankshaft: I suppose because CRT Monitor work at higher frequencies respect to normal TV.

              Ciao
              Gianni
              "In the confrontation between the stream and the rock, the stream always wins...Not through strength, but through persistence."
              H. J. Brown

                Comment

                • Wizard
                  Badcaps Legend
                  • Mar 2008
                  • 2296
                  #5
                  Re: Hp Mx70

                  And far more sensitive and need to shield magnetic leakage.

                  Cheers, Wizard

                    Comment

                    Previous template Next

                    Related Topics

                    Collapse
                    • tony359
                      Bipolar capacitor for vintage Apple CRT monitor
                      by tony359
                      Good day all,

                      I have a question about some old monochrome Apple monitors.

                      Inside those monitors there is one bipolar capacitor. From the schematics I have it's part of the horizontal linearity circuit.

                      A friend replaced a bipolar 4.7uF 25V capacitor with a Nichicon bipolar 4.7uF 25V. The cap popped after about one hour. The new capacitor was much smaller than the original one but that's not a surprise as the original one was from 1980. (I am not sure whether the original was was actually 4uF and was replaced with a 4.7uF?)

                      The new capacitor:...
                      08-12-2024, 03:27 AM
                    • Amminadabz
                      What to replace an unobtainable bipolar elctrolytic?
                      by Amminadabz
                      Howdy folks, its been a minute.

                      I'm working on a capacitor kit for my Korg C-15 digital piano, and it has a couple bipolar electrolytics (C27 and C34) on the analog board for which I can only find one direct replacement, but it's sold in multiples of 50.

                      I've got a couple work-arounds in mind (Ebay NOS, testing with the og part, swapping for a ceramic), but what part can I recommend that will be reliably obtainable in the future? Would a ceramic or MLCC (not entirely sure what the practical difference is) be a good general replacement for bipolar electrolytics? It's...
                      03-26-2023, 04:12 PM
                    • earz
                      Removing large LCD panels
                      by earz
                      I'm curious what techniques everyone uses to remove/move/lift large LCD TV panels when doing backlight repairs. I typically use two large suction cups, but lifting a 65" panel off a LG a month ago and I got a little too close to the wall and accidentally crammed the corner of the panel into the wall (gouged the drywall even) which resulted in a single crack all the way across the panel. Thankfully I just do this as a hobby on TV's that I scrounge up to repair and sell, so I didn't have to make a dreaded phone call to a customer.

                      That incident got me thinking about making some...
                      05-19-2021, 10:42 PM
                    • Adenitz
                      Replace electrolytic cap with bipolar one
                      by Adenitz
                      Hello,
                      can I use this cap:
                      https://www.tme.eu/en/details/ues1h4...tors/nichicon/

                      Capacitor: electrolytic; bipolar; THT; 47uF; 50V

                      to replace this capacitor: Electrolytic Radial E 47uF/50V 6.3x11 RM2.5 105°C Jamicon

                      What exactly I can expect to install bipolar electrolytic cap instead a regular one?

                      Thanks.
                      02-02-2022, 07:44 AM
                    • srs
                      Insignia NS-50DR620NA18 w/ large vertical lines & no picture
                      by srs
                      I'm not sure what to do next and came here since y'all helped me fix a 50" plasma TV back in 2014, which is still working!

                      A friend gave me an Insignia NS-50DR620NA18 50" TV that suddenly developed large vertical lines on it. He said he had no idea what might have caused it and has replaced it with a larger TV. He was going to throw it away.

                      I did not notice any bulged or leaking caps on any board, the voltages produced by the power supply match the voltage that the pins are marked. The backlight leds are working. I have tried cleaning the ribbon cables...
                      04-22-2023, 02:40 PM
                    • Loading...
                    • No more items.
                    Working...