Hitachi with MS9 low focus

[kernelchagi]

Hello. I have a recapped nanao ms9 with an hitachi tube. The monitor is losing focus when i turn up the contrast to what i consider "normal" levels. Convergence was messy but i fix it already touching the rings.
Could this focus problem improve with a new flyback? I have a new flyback compatible (not original) wich i could try, but im not sure if it gonna improve something.

Maybe i G1 mod the nanao and this will help? Besides this the monitor looks good with no burn.

[nem]

I would try rejuvenating the tube.

[thegreathopper]

Sounds like your monitor has done a lot of hours, may just be an age thing.

[PrincessPrinPrin]

This is something that can be diagnosed easily with a HV probe. You check voltage with focus wire disconnected from CRT socket and if lower than normal it's the flyback whereas if it's at the correct level and adjustable it's the socket or the tube. Focus voltage is ususally 25 to 30% of anode voltage.

[nakajima]

is your chassis a ms9-29SU or is it another ms9?

I understand that the specifications for the Hitachi tube are slightly different.

A friend indicated that if a different MS9 chassis is used in Hitachi tube, the resistor R532 must be changed to 1.5Ohm 1W (instead of a 3.3Ohm). Please, can someone with more technical knowledge confirm this?

@Nebula ?

[grantspain]

do that heater resistor value change first

[kernelchagi]

do that heater resistor value change first

Ok thanks a lot gonna have a look. Btw whats your opinion on the g1 mod of this thing? Why do you think it has all the circuit made but they didnt decide to include it at the end?

[grantspain]

never done that g1 mod, i did remember seeing a post about some time ago
replacing that resistor is a 5 minute job with little expense so try that first, the problem is not knowing whether your tube is weak or just not matched to the chassis

[chriszhxi]

I have a ms9-29t(pcb D1), a ms9 auto switch without label(pcb C1), they are just as sharp as my Toshiba PD1843 or PD2367, I also have a ms9-29N22(pcb C1) and a ms9-29NDR23W, they are not as sharp as previous two. Those are all recapped, so it really depends on the chassis itself, I don't think mod is needed.