MS2930 comes into focus after ~5 minutes: new caps and flyback

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    • MS2930 comes into focus after ~5 minutes: new caps and flyback

      Hi All,
      My MS2930 was acting strangely
      -popping
      -picture not always appearing on start up

      So I recapped it and had similar results minus the popping.

      I decided to try a replacement flyback, same as here in my 2931 arcade-projects.com/forums/ind…-screen-randomly-expands/

      I did adjust the HV pot as well to reduce the picture size like on the 2931 in the thread above. I have not checked the B+ voltage as I've been unable to locate and information on what this value should be for the 2930.
      Everything looks good now however the image on screen is reduced in size and out of focus on start up. After about 5 minutes the picture enlarges and then comes into focus. Its not a huge deal but I'd like to address it if I am able. Also hoping it is not indicative of a failing tube?

      Most of what I am finding online is suggesting that the flyback should be replaced... I do have another spare that I am thinking of trying out. I have also seen some suggestions to clean/inspect the neckboard/socket.

      Has anybody had a similar experience to this? Can anyone provide B+ information for this monitor?

      EDIT: after 15 minutes of being shut down then powering back on the image looks good on startup. It takes maybe an hour of being shut down for it to "lose focus"

      images here

      Thanks much,
      -Andy

      The post was edited 1 time, last by snakeGrave: more details ().

    • snakeGrave wrote:

      I decided to try a replacement flyback, same as here in my 2931 arcade-projects.com/forums/ind…-screen-randomly-expands/

      I did adjust the HV pot as well to reduce the picture size like on the 2931 in the thread above. I have not checked the B+ voltage as I've been unable to locate and information on what this value should be for the 2930.
      Everything looks good now however the image on screen is reduced in size and out of focus on start up. After about 5 minutes the picture enlarges and then comes into focus. Its not a huge deal but I'd like to address it if I am able. Also hoping it is not indicative of a failing tube?

      Most of what I am finding online is suggesting that the flyback should be replaced... I do have another spare that I am thinking of trying out. I have also seen some suggestions to clean/inspect the neckboard/socket.

      Has anybody had a similar experience to this? Can anyone provide B+ information for this monitor?

      EDIT: after 15 minutes of being shut down then powering back on the image looks good on startup. It takes maybe an hour of being shut down for it to "lose focus"

      nem wrote:

      Which part of the of OP did you actually read? He did the flyback and he's not losing focus.

      Although this said, maybe the replacement flyback is a dud. Swapping it doesn't take that long. Might as well rule that one out.
      Okay...first @nem, I am going to give you the benefit of the doubt, that you did not mean this, as condescending and discourteous as it comes across.

      I read the post. It very clearly states, that he did replace the flyback, and NOW the picture starts out of focus, warms up into focus after five minutes, and if you power the monitor down for an hour, and boot it back up, it comes up with no focus again.

      He says he has another spare flyback to try....which I was suggesting he should.

      That loss of focus, and regaining it on warm up, is usually a failing flyback, as notated here - repairfaq.cis.upenn.edu/Misc/REPAIR/F_monfaqb.html - which also contains testing instructions on how to ensure that the diagnosis is accurate, rather than the issue being with the tube, or with components on the neckboard.

      It's entirely possible that the currently installed, replacement flyback has issues, especially if it was used, which I assume it is, as to my knowledge, flybacks for this series are unobtanium.

      I'm perfectly fine with any guidance I put forth, being taken with a grain of salt...as i'm not an expert at any repair discipline, only reasonably competent at a few. However, I most assuredly attempt to read, before contributing.
    • Hey guys first off thanks for your input!


      Yes I am thinking it is a good idea to try my last spare flyback or maybe the one from my previous thread where it made the screen "expand".

      I actually ended up having more issues with this monitor last night while I was fooling around with it. The amount of blue in the picture shot off the charts. I tracked the source of that problem down to a tiny bjt on the neckboard it had developed a short between two of its legs. I suspect it was cause by me messing with the HV pot like a dummy. Once pulled the picture looked better... which I found weird. I ordered what I think are suitable replacements(BF299) and will pop them in when they arrive. I will also pop in my last flyback in the meantime to see if that makes a difference.

      EDIT: also @nem I used a capcit from arcade parts repair. Some of the voltage values seem to be rated higher than on the original caps but the capacitance values are the same

      The post was edited 2 times, last by snakeGrave ().

    • did you say the picture size is small when out of focus?
      if yes then it could be the b+ low or unstable, you would need to monitor the b+ to see what is happening- the b+ at fuse F701 and should be between 175 and 180v

      i do know of other issues where focus can be out and then snap in ok, this can be down to the crt socket itself- they can become corroded or oxidised
    • @gunblade
      yes it is slightly reduced in size at start up when it is out of focus, maybe 2 inches on each side and also bad pincushioning.

      I did check the B+ yesterday after I found your post in another thread it was pretty spot on at 180V I however can not recall if I checked it while the image was in focus or not. I will take a measurement at start up and after 5 minutes of running next time and take note.

      I have been wondering about the crt socket since this monitor was quite dirty. Where is the best place to source a socket? are they standard among CRTs? Seems like another inexpensive fix that is worth doing while I have the monitor out of the cabinet.

      EDIT: it looks like a 9 pin socket?
    • i am trying to work out if you have two seperate faults or one, a low b+ will cause size issues but would need to be very low to cause a focus problem. The pincushion can be down to low b+ but can also be down to an issue in the horizontal size circuit

      the crt socket is standard 9 pin type, plenty of stockists in the US i would imagine

      i do not think this is a flyback issue but who knows, imo you should monitor that b+ on cold start and report back
    • Cap kit caps can be sometimes off. Do you remember replacing a physically larger sized cap with a smaller one? Like this:

      Sharp Image Repair (CRT Repair service in Las Vegas, USA)

      bagheera369 wrote:

      Okay...first @nem, I am going to give you the benefit of the doubt, that you did not mean this, as condescending and discourteous as it comes across.

      Nah, you shouldn't have given me the benefit of the doubt. Re-reading it now it did come off as an asshole reply from me. Apologies.

      My guess is the replacement flyback won't fix this issue, but it's good to rule things out, especially since it's a 15 minute job.
    • nem wrote:

      Cap kit caps can be sometimes off. Do you remember replacing a physically larger sized cap with a smaller one? Like this:

      Sharp Image Repair (CRT Repair service in Las Vegas, USA)

      bagheera369 wrote:

      Okay...first @nem, I am going to give you the benefit of the doubt, that you did not mean this, as condescending and discourteous as it comes across.
      Nah, you shouldn't have given me the benefit of the doubt. Re-reading it now it did come off as an asshole reply from me. Apologies.

      My guess is the replacement flyback won't fix this issue, but it's good to rule things out, especially since it's a 15 minute job.
      Apology accepted sir. We're all just trying to lend a hand, where we can. :D
    • @nem yeah here is a picture of C703 soldered into my chassis

      the one from the kit is definitely reduced in size... I'll try and grab a more appropriate replacement I am having a hard time finding low esr caps rated for 250V and above

      EDIT: I found these but I'm skeptical and cant seem to locate a datasheet

      EDIT2: I'm considering trying these unless someone here has reason to suggest it is a foolish idea :P the listed ESR is .08 ohm compared to the .2 ohm that nem measured in his linked to post. Also Aluminum organic?

      The post was edited 1 time, last by snakeGrave ().

    • snakeGrave wrote:

      EDIT2: I'm considering trying these unless someone here has reason to suggest it is a foolish idea

      @Hatsune Mike used aluminum organic caps in his MS9-29 Solid-State "High Life" capacitor replacement kit.

      I think that's the cap I would go for. I won't promise it will make any lick of difference, but at least it will be more in spec than whatever you have there currently.
    • Do also be careful when fitting in more modern low ESR caps that it doesn't have a degenerative effect on circuits that rely on a particular ESR. A good example would be filter capacitors for the input and output of an LDO. I got bit by this when I recapped my PFX with mostly solid state caps. One 330uF cap had to be reverted to an electrolytic because I otherwise got a pretty ugly jailbar pattern on the screen.

      For the MS9 though, they have been working great.
    • -swapped out the caps for low esr ones
      -replaced the socket on the neck board
      -reflowed some joints
      -swapped out janky anode cap for one from the stock flyback

      Still somewhat erratic when powering up. I did recently get something to read humidity in the room and it appears as though this crt is pretty sensitive to varying humidity.

      I fired it up with ~ 70% humidity and it took far longer to come into focus than a day or two later when it was ~ 50% humidity in the room. Some days it fires right up in focus, I did not have the means to measure humidity on these days.

      My other MS2931 monitors don't seem to mind the varying humidity though... does this make much sense?
      -
    • New

      Switched out the fly back again with one from a different batch I guess.

      I tried two from a batch that was labeled 20200501 and both gave funky focal results. I’m pretty sure that I have one from that batch in my other ms2931 though and it’s been working great.

      I tried one from a different order, labeled 20191102 and everything seems to be working out nicely after some minor adjustments.

      still need to run it for a few hours to see if the results hold up but it is looking like it was indeed a fly back issue. Thanks for the help!

      The post was edited 1 time, last by snakeGrave ().