153 - Pure analog goodness - Marconi TF2331 THD meter - but will it work?

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  • เผยแพร่เมื่อ 7 ม.ค. 2025

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  • @noakeswalker
    @noakeswalker 8 หลายเดือนก่อน +2

    Good fix for the sticky meter. I have had meters do that in the past, and it's usually been due to particles attracted to the magnet periodically jamming/slowing the meter movement. That hinged pcb construction used to be much more common back then I think - I've owned radio gear that was a joy to fix/modify because of this.

  • @davestorr6764
    @davestorr6764 8 หลายเดือนก่อน +1

    …..nice 🙂 That’s a beast of a chassis. I think for part 2 maybe the strip of cardboard could see an upgrade? Another great repair video, thanks.

  • @t1d100
    @t1d100 8 หลายเดือนก่อน +1

    Kudos to you, for a great find and repair! Yes, part 2, please. Kudos to geirendre (hardened grease,) jim (tiny scope) and cashew (PCB face,) for their comments. Tip = Many drawing programs have a function that will expand an array into an arc. So, you could make your own meter face. Even some of the open source offerings do this. If you have a 3D printer, you could make a decorative name plate, to replace the black cardboard (however, it is perfectly fine.) Cheers.

    • @TheHWcave
      @TheHWcave  8 หลายเดือนก่อน

      sadly no 3d printing (yet), of course I could always find a place that allows me to do a 3d print job. I could make new scale (done it before, last time for a high voltage meter, there is a video...) but I am wondering if the small meter dimensions is making this worth the effort

  • @davidv1289
    @davidv1289 8 หลายเดือนก่อน +1

    Well done! That is a very interesting chassis, I have seen a few pieces of HP gear with fold-out cards but not hinged chassis sections. As someone else suggested, you might try backing off the jewel tensioning screw (just a few degrees at a time, front and/or rear) and see if the original meter movement improves - can't hurt it. Regards, David

    • @TheHWcave
      @TheHWcave  8 หลายเดือนก่อน

      Yes, could try that. I am currently on a business trip so it will have to wait until I am back

  • @geirendre
    @geirendre 8 หลายเดือนก่อน +2

    8:00 My TF2331 doesn't have a shield over the distortion PCB eighther.
    I'm considering taking the shield from the powersupply and moving it there.
    I will be running mine from a DC power source anyways.
    BTW the 4 transistors on the distortion pcb was placed in sockets and the legs was corroded,
    so I removed the sockets and soldered the transistors directly to the pcb.
    Also i replaced the banana input jacks with new high quality ones.

    • @TheHWcave
      @TheHWcave  8 หลายเดือนก่อน

      Good tips, many thanks. Yes I may move the shield from the power supply. So far ethe distortion part has not given any trouble and the wild deflections caused by the phase knob are getting better (probably because I am using the pot more)

    • @geirendre
      @geirendre 8 หลายเดือนก่อน

      @@TheHWcave Just finished recapping and servicing (cleaning switches etc) mine TF2331, and it works great now.
      The manual states a current draw of 25mA, and mine clocks in at 24mA.
      Connected to my Uni-T AWG supplying a 1KHz tone I'm now able to dial it down to around 0.015 - 0.02% distortion.

    • @TheHWcave
      @TheHWcave  8 หลายเดือนก่อน

      @@geirendre Out of interest, did you do all electrolytic caps in all parts?

    • @geirendre
      @geirendre 8 หลายเดือนก่อน +1

      @@TheHWcave I ended up replacing all the orange/red caps.
      I measured the first few that I took out, and they all measured high, and with some level of leakage.
      So I decided to do them all. The only few I left was some small caps that I was not sure if where tantalum,
      they measured ok, so I left then in.
      There was also a few papercaps (Dubilier branded) that I replaces.

    • @TheHWcave
      @TheHWcave  8 หลายเดือนก่อน

      @@geirendre thanks for the info. I may have a good look at the other caps then

  • @ivolol
    @ivolol 8 หลายเดือนก่อน +1

    Could also do 330 ohms R + 100 ohms trimpot.
    If the instrument uses 10x and 3x units full scale ranges, I would be tempted to take a photo of the new meter's scale backsheet and then photoshop up a custom one with with both scales.

    • @TheHWcave
      @TheHWcave  8 หลายเดือนก่อน

      I thought about making a new scale but not sure if it would be worth doing. I may look into it ...

  • @geirendre
    @geirendre 8 หลายเดือนก่อน +1

    Nice, I Just got one og these meters myself.
    It worked on DC supply for 1 hour, then the notchfilter part stopped working.
    Havent had the time to look into whats wrong with it.
    Looking forward to part 2 of this.
    BTW did you try to loosen on the tiny screws on the needle in the instrument?
    Could be that it is stuck in old hardened oil.

    • @TheHWcave
      @TheHWcave  8 หลายเดือนก่อน

      No I have not touch them but will give it a try (I am currently on a business trip and not at home)

    • @geirendre
      @geirendre 8 หลายเดือนก่อน

      @@TheHWcave Just take one screw at a time or else you risk that the movement falls out.
      Lossen one screw a tiny bit, flush the bearing with IPA, and tighten the screw until the movement starts to drag, then back it of "just a smidge".
      Then do the same on the other screw.
      Everything looked ok in your instrument, so it must be something with the bearings,
      lets just hope you can clean it up.

  • @milantrcka121
    @milantrcka121 8 หลายเดือนก่อน +3

    Try to move the needle mechanically. If it drags, check the movement for the presence of ferromagnetic debris interfering with the movement of the coil frame. My old analog volt/amp meter (Avomet) had a similar problem. Tiny chip was removed with a steel wire to which the chip was attracted.

    • @TheHWcave
      @TheHWcave  8 หลายเดือนก่อน

      Ok, good call, I will check for debris

  • @jim9930
    @jim9930 8 หลายเดือนก่อน

    I would have been tempted to use a tiny oscilloscope instead of a different meter. Nice to see the waveform as you null.

    • @TheHWcave
      @TheHWcave  8 หลายเดือนก่อน

      I have connected a scope to the analog output (going to be in part 2. Its interesting but not really suitable for minimizing.

  • @cashewmilkfan
    @cashewmilkfan 8 หลายเดือนก่อน

    you can recreate an analog meter face as a 0.6 mm pcb and have it come out very clear and precise if you get it fabricated

    • @TheHWcave
      @TheHWcave  8 หลายเดือนก่อน

      i have done my own in the past by taking a photo and then editing a new scale, then printing it on good card material, I will consider that. Thanks