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Naomi CRT Swap issue
lilshawn:
--- Quote from: ID4 on June 29, 2022, 06:18:13 am ---
Toshiba (A68KSM696X):
Lh 0.196mh
Lv 13.8mh
Rh 0.6 ohms
Rv 6.9 ohms
I have another philips tube (A68ESF002X43):
Lh 0,309 mh
Lv 5,2 mh
Rh 0.340 ohms
Rv 4,680 ohms
Remember that I'm using a philips tube (A68ESF002X11) with the Toshiba original yoke (A68KSM696X)
If I hypothetically use directly the A68ESF002X43 philips tube including his original yoke, with the nanao or the sanwa chassis, I would have to modify the chassis to make it compatible with the philips yoke's Lv 5,2 mh, in that case what capacitos need to be changed? and what values?
--- End quote ---
unfortunately, major modifications such as this are outside the scope of my expertise... but with the inductance values of those coils being as out as far as they are with each other as they are, i suspect the donor tube's yoke has been designed with its own frequency in mind and modifying the cassis enough to drive it would greatly reduce the yokes lifetime... allow me to explain a bit.
when a company designs a yoke for a tube, you tune it to be near the oscillation frequency you plan the ultimate output to be. ideally you'd have it at the same frequency as a single scanline to be the most efficient. of course, there is a fair bit of leeway either way and we often sacrifice efficiency for the convenience of an already existing off-the-shelf part by tweaking the tuning.
there is a particular model of monitor that is capable of switching frequencies between 15khz, 25khz, and 31khz... the yokes are disintegrating on them because when operated out of their manufactured ideal range... while they do "work", they produce copious amounts of heat, making the plastics and resins in them used to build them and hold them together, break down and literally fall apart. the reason for this is that different value yokes are used for lower frequency monitors (single frequency) opposed to those monitors that operate in higher frequency resolutions. trying to "shoehorn" a yoke that was made to display a particular frequency, and be driven using a completely different frequency, is really bad for it. tweaking a little bit is okay, but with the values your suggested replacement has, way too much.
while I don't doubt you COULD get this yoke to work with whatever resolution your original monitor is, whether you SOULD or not depends on how long that yoke is going to last being driven under those conditions. like, if your donor LH was 0.201 or 0.180 id say you could probably be fine swapping it and just adjust some settings and be good, but being 0.113 out is too much to just yolo it. you can also tell your donor tube runs a way different resolution than your existing tube, just by the vertical yoke value. 5.2 vs 13.8 if the donor was 4 to 6...maybe.
again, I'm not saying it's impossible, its just you have to factor in how the yoke itself was originally designed and kind of work with that as well.
ID4:
--- Quote from: lilshawn on June 29, 2022, 10:42:01 am ---
unfortunately, major modifications such as this are outside the scope of my expertise... but with the inductance values of those coils being as out as far as they are with each other as they are, i suspect the donor tube's yoke has been designed with its own frequency in mind and modifying the cassis enough to drive it would greatly reduce the yokes lifetime... allow me to explain a bit.
when a company designs a yoke for a tube, you tune it to be near the oscillation frequency you plan the ultimate output to be. ideally you'd have it at the same frequency as a single scanline to be the most efficient. of course, there is a fair bit of leeway either way and we often sacrifice efficiency for the convenience of an already existing off-the-shelf part by tweaking the tuning.
there is a particular model of monitor that is capable of switching frequencies between 15khz, 25khz, and 31khz... the yokes are disintegrating on them because when operated out of their manufactured ideal range... while they do "work", they produce copious amounts of heat, making the plastics and resins in them used to build them and hold them together, break down and literally fall apart. the reason for this is that different value yokes are used for lower frequency monitors (single frequency) opposed to those monitors that operate in higher frequency resolutions. trying to "shoehorn" a yoke that was made to display a particular frequency, and be driven using a completely different frequency, is really bad for it. tweaking a little bit is okay, but with the values your suggested replacement has, way too much.
while I don't doubt you COULD get this yoke to work with whatever resolution your original monitor is, whether you SOULD or not depends on how long that yoke is going to last being driven under those conditions. like, if your donor LH was 0.201 or 0.180 id say you could probably be fine swapping it and just adjust some settings and be good, but being 0.113 out is too much to just yolo it. you can also tell your donor tube runs a way different resolution than your existing tube, just by the vertical yoke value. 5.2 vs 13.8 if the donor was 4 to 6...maybe.
again, I'm not saying it's impossible, its just you have to factor in how the yoke itself was originally designed and kind of work with that as well.
--- End quote ---
Hi!
Thank you for the very useful explanation.
Ok That is if I combine the A68ESF002X43 tube and yoke with the Nanao or Sanwa chassis, I will not do that, is better to keep using the A68ESF002X11 with the Toshiba original yoke and fix the magnetic issue.
In another way I have two Hantarex Polo Star that I know are directly compatible with the A68ESF002X43, that is another optión although I prefer to use the nanao, so this is last option.
Thanks!
ID4
EvilSal66:
Hi to all, i'm new in this forum, i saw this topic and I wanted to ask if in the end the swap of the tube was a success or not. Thanks
ID4:
Hi!
Finally I have managed to make the tube swap successfully :applaud: (sorry for the delay), as soon as I have time I will present details and conclusions.
ID4:
Hi!
The problem is that to make the toshiba tube yoke fit well with the philips tube, the yoke has to slide further in, and the philips tube is depeer than others, so it doesn't allow the yoke to slide further, as you can see in this photo from arcade proyects:
https://www.arcade-projects.com/attachments/ms9comp-jpg.53807/
So there was no way for the image to fit correctly, perhaps someone with more knowledge could be able to adjust it, but it seems that there is no way precisely because of the depth of the tube
I could use the philips tube with its original yoke changing the chassis for a Polo Star one, I tried it and works perfectly but the idea is to use the MS2932 chassis.
So I decided to try with another tube, I have found a tube that has less depth than the philips, taken from an LG TV
And WOW It has worked perfectly with toshiba tube yoke and MS2932 chassis, I haven't even entertained in a tight fit, just a basic fit, even the curvature fits to the millimeter with the bezel of the Naomi: