Problem Toei Chassis/Tube Swap

[jerryspaghetti]

Ok this is a little complex but here goes....

I have two 25 inch monitors that originally had Toei Chassis. The two chassis were beyond repair & missing entirely from the monitors.

After a good bit of research I narrowed replacements down to Nanao MS8 and MS9 chassis. Not all will work but specific models are supposed to with some minor adjustments needed.]

So I done some tube testing with the Nanao chassis and have the following results...

Toshiba tube A59JMZ90X
MS9-29 chassis - Very narrow image and screen bows when try to fill horizontally even with jumper in Wide position (SEE PIC 1). Possibly needs a resistor changed on the neck board according to forums?
As an experiment I also tried...
MS8-29 chassis - Full coloured decent image but screen is strobing/flashing. May not be compatible at all with this tube.
MS8-25FTB chassis - Weak colours, weak performance from flyback including raster lines even when dimmed to near total dark. Bad geometry. Suspect a faulty chassis as below.

Hitachi tube A59KFS61X10
MS8-29 chassis - Worked ok but a little soft and a very dim image even with flyback/brightness/contrast ramped up (SEE PIC 2). Resistor for heater will need to be changed to increase brightness. Not sure if this will solve the sharpness though....
MS8-25FTB chassis - Weak colours, weak performance from flyback including raster lines even when dimmed to near total dark. Bad geometry. Suspect a faulty chassis as others have reported better results with this set up. Will get it serviced and do more tests…
MS9-29 chassis - Worked almost perfect. Very crisp and clear but horizontal width cannot be fully adjusted to fill whole screen even with jumper set to Wide (SEE PIC 3) UPDATE I adjusted B+ (needed to go up 7-8v which may be risky) and fills the screen horizontally with a nice sharp image which can be fully adjusted by all controls (SEE PIC 4 and link to YouTube vid)

Thanks for all the advice so far. Will continue to test and hopefully save others the heartache later.

 

[TheDaddy]

I have just started to look into CRT screens as I have never messed before , What a mind field ! Did you read this with the universal chassis ??

https://www.ukvac.com/forum/threads/are-these-any-good.86715/#post-601319

Wont be as good as what you have if you can get them working but always an alternative incase.

Dave.

 

[jerryspaghetti]

I actually do have a decent quality Intervideo Universal Chassis which is superior to the cheap Chinese ones but I may pick one up just to see what they're like.

If I did i'd definitely reflow the whole thing and probably upgrade all the caps before hooking it up. Would make a serious difference i'd expect.

 

[TheDaddy]

If you do update us on if they any good !!! I would personally check for dry / bad joints and fire it up and use. Replaced caps if and when needed !

Yeh them Intervideo ones look better quality !

Dave.

 

[jerryspaghetti]

If you do update us on if they any good !!! I would personally check for dry / bad joints and fire it up and use. Replaced caps if and when needed !

Yeh them Intervideo ones look better quality !

Dave.

Will do mate. It's on the ever growing list of things i'll never do. Just below the skirting in the hallway

 

[gunblade]

you need to read the inductance and impedance of the yokes to make sure they match the chassis
heater resistor is easy to find, follow the heater pin from the crt socket to the chassis - if picture is too dark halve the value of the resistor

 

[jerryspaghetti]

you need to read the inductance and impedance of the yokes to make sure they match the chassis
heater resistor is easy to find, follow the heater pin from the crt socket to the chassis - if picture is too dark halve the value of the resistor

Excellent, will look at that resistor and double check the impedance. Not sure I have the meter to read inductance. Need to check.

 

[gunblade]

the inductance reading is critical when matching yokes to chassis

 

[jerryspaghetti]

the inductance reading is critical when matching yokes to chassis

See I never even considered it. Everything I read mentioned yoke impedance and neck size/socket type but never the inductance. So annoying

Would that explain the narrow screen or the strobing one?

 

[gunblade]

perhaps you have a fault on the ms9, try it on the other tube - ms9 have a horizontal size limit pot as well as width jumper and horizontal size

 

[jerryspaghetti]

perhaps you have a fault on the ms9, try it on the other tube - ms9 have a horizontal size limit pot as well as width jumper and horizontal size

MS9 working well on its own tube

Will try it on the other tube also

 

[jerryspaghetti]

So MS9 works almost perfectly in the Hitachi tube but about 25mm narrow either side (See Pic) even with the jumper set to wide.
Adjustment of remote board and pots on side of chassis helped pin cushion but couldnt stretch the screen to full width.

 

[gunblade]

h.s lim not helping at all?

 

[jerryspaghetti]

h.s lim not helping at all?

I'll give it another go tonight but tried every pot on the remote and the side of the chassis itself and this was the best I could get.

If I increase the horizontal on the remote or the chassis anymore it just starts bowing top and bottom and stays where it is in the middle. Bowtie shaped is the best I can describe it as but will get some more pictures later.

Its soooo close!

 

[gunblade]

next step if h.s lim does not help is to check the b+ is 75v if its running at 15khz

 

[jerryspaghetti]

next step if h.s lim does not help is to check the b+ is 75v if its running at 15khz

Excellent, i'll try that. Need to work out where to connect the multimeter for that test

 

[gunblade]

r967, the large ceramic resistor and heatshield for ground

 

[jerryspaghetti]

r967, the large ceramic resistor and heatshield for ground

Thanks man

 

[jerryspaghetti]

St Patricks weekend got me too wobbly to mess with these but just about recovered and will have another look at these tonight.

I have found this handy webpage that alludes to the resistor swap but would need expert opinion on what to do with that resistor....

https://gamerepair.info/hardware/35_nanao_ms9_29

The tube i'm very close to pairing (albeit with the slightly narrow image) is a Hitachi A59KFS61X10. So is R532 the resistor that needs replacing to solve my width issue? And what resistor should I replace with? I'm referring specifically to the passage....

''Like many tubes, the A68KJU96X is designed to have a heater voltage of 6.3V. This voltage is a function of the resistance of the heater filament as well as the current-limiting resistor.
The heater resistor for the MS9-29 is located at R532, and is tucked between the LOPT (Flyback) and the heatsink.
On the MS9-29N22, MS9-29T, and other submodels that are intended for use with the A68KJU96X tube, the heater resistor is a 3.3 ohm resistor.''
Thanks

 

[thegreathopper]

I don’t think that affects the width is more to do with the contrast.

Check this thread, I swapped the 3.3 for a 1.5 ohm resistor.

Nanao chassis, Hitachi tube?

I received two Super Neo 29 Candy cabs today, and I'm excited to get them up and running. The seller shipped them with the original Hitachi A68LFP227X tubes, but said that the Toshiba chassis were dead and he was including a pair of Nanao MS9 chassis instead. But... The connectors are...

www.arcade-projects.com