Nanao MS9-29S Monitor Issue (Sega New Astro City 29")

[billd420]

Just this past week my 29" nanao in my New Astro City cabinet developed an issue I have yet to encounter. When the monitor first turns on, only the top 1-2 inches get scrunched into a thin beam that rest on top of the picture. The rest of the picture is unaffected. After about a minute of being powered on, the issue goes away. This screams that a component is failing, or completely failed.

I don't even know where to start with this problem, or if its even worth investigating now. I'm just worried if the faulty part breaks completely that it will take other components with it.

Please help!
Thanks,
Bill

[Singapura]

Have you tried posting your question on killercabs.com? There seem to be a lot of Astro owners there.

[grantspain]

hey Bill,
What you been doing to the Kc boys,anyways its gonna be an electrolitic in the horizontal frame circuit,swap out the caps around U550 LA7852-not certain but it sounds the best bet

[billd420]

its gonna be an electrolitic in the horizontal frame circuit,swap out the caps around U550 LA7852-not certain but it sounds the best bet

I'll investigate the caps in that area. I have yet to touch ANY of the caps or chassis for that matter on this Nanao. I'm pretty confident your advise will help, as you hit the nail right on the head last time my other nanao had an issue.

Thanks for the assistance Grant!

[billd420]

For the first time in months, I had the opportunity revisit the problem my Nanao MS9-29S is experiencing. In my first post (which I corrected), I thought the chassis was a MS9-29A. After cleaning it very well, I found out it was a MS9-29S. Also, since the first post, the "thin beam" across the top has turned into the image wrapping over the top of the undistorted raster (hard to explain, see pics below).

As per Grant's suggestion, I went ahead and recapped the caps around position U550. In addition, I went ahead and recapped just about all of the caps except for the high voltage ones. Unfortunately, after replacing 30 or so caps, I'm still experiencing the problem.

I accidentally bought the wrong size for one of the caps I was planning on replacing (shown below), so that one was not swapped out. Also, cap C411 (50v22uf) was originally a non-polarized cap. I didn't realize this until I pulled the old one. I went ahead and installed the polarized cap of the same rating. Will this make a difference? Should I switch to non-polar?

Here are some pics of what I'm experiencing, as well a diagram for which caps I replaced. I was sure to use high temp caps throughout, and all were exact matches.



Red = Caps I replaced
Blue = The cap that was originally non-polar which is now polarized
Orange = The cap I planned on swapping but bought the wrong size
Green = The HV (i think?) caps that I did not touch


Here is what the monitor was doing before and after I swapped in the new caps outlined above:



Does anyone have any suggestions on where I should look next?

Thanks for any help!
Bill

[grantspain]

the problem is gonna be around u401,check the diodes and resistors
the bp cap is c411 which my schem say is 2.2uf 50v BP
check q401
what happens when you adjust vr402?

[billd420]

Hi Grant-

First off, thanks for the quick reply, and my apologies for the slow reply. I haven't got a chance to look into the monitor again until now. I had a few questions before I start tinkering. The monitor is assembled again and installed back into the Astro city. I plan on pulling it either today or tomorrow to do some more investigating. Side note, my geometry (aside from the top of the screen), color purity and brightness are STELLAR since I shotgunned all of the caps

the problem is gonna be around u401,check the diodes and resistors

For the life of me I can't find the schematic for the MS9 (I own a manual, but its MIA right now). Do you have the correct diode and resistor values for the area you want me to check out? Also, I should be OK checking these components in circuit, right? Or, do they need to be removed to be tested?

the bp cap is c411 which my schem say is 2.2uf 50v BP

I'll go ahead and swap in a bi-polar cap instead of the polarized one thats there. Not sure if it will change anything, but I'd prefer the chassis to stay as close to schematic spec as possible.

check q401

Without the chassis or schematic right in front of me, which component is q401, and approximately where is it located?

what happens when you adjust vr402?

I'll tinker with this and report back.


Again, thank you so much for your assistance thus far! You're the best!

[grantspain]

i think it will be the vertical size limit,vr402
everything on the picture looks spot on so its possible this has been adjusted in the past

any other kind of problem would throw up other symptoms

[billd420]

Hey Grant-

Today I checked around u401, and all of the diodes passed my DMM's diode test (in circuit), and all of the resistors showed significant resistance (again in circuit).

q401 showed .480v while in circuit, not sure if this is the desirable value, however it wasn't shorted.

I tinkered with vr402, and the problem with the monitor grew with the rest of the raster, so no luck there.

The one thing I did discover is r427 (as pictured below) is showing continuity (gasp!), so I'm fairly certain the part has failed. I'm not positive here, but I believe thats a resistor (doesn't look like the other colored + banded ones I'm used to seeing). When I measured the resistance, my DMM showed 01.1ohms in circuit, and told me it was shorted via beep test. The component is stamped 1Ω•J. What is the correct replacement part that I should pick up?



If that faulty component is indeed the source of my troubles, is it potential that it took out other components with it?

Thanks for your help thus far, and any additional insight you may provide!

-Bill

[grantspain]

thats reading correct, its a 1ohm resistor
this fault i have not seen on the ms9 so i am just guessing now tbh,c513 try changing that
see similar faults on other chassis and it has always been a slightly unstable 25v on the vert frame ic

[billd420]

Thanks for the reply Grant. Bummer you haven't encountered this issue before.

I'll look into c513 assuming I haven't already changed it out (I did most of the caps on this chassis already).

Can you recommend a test point to see if the Vert. Frame IC is getting 25v?

It should also be noted that the issue appears to have gotten slightly worse since I posted pictures of the dot cross hatch. As of right now, I can't get anything to show on the top 1" to 1.5" of the monitor. After the picture hits the highest spot, it wraps over to the back, only mirrored.

Since everything else works flawless on this monitor, do you think that one of the IC's has blown? I still personally think there's a bad cap or resistor somewhere giving an IC the improper maximum height value... however I'm still a n00b when it comes to monitors

Thanks,
Bill

[billd420]

Quick update- c513 has already been replaced with an exact match cap.

Any more ideas before I ask Jomac if I can send it in for repair?

-Bill

[grantspain]

yeah i got lots of ideas,whether you want to mess with them is the question
could be ic401,a bad transistor,a cap somewhere

[billd420]

Grant-

How do I go about testing IC401? Is there a datasheet somewhere I can reference? Also, will I need a logic probe to trouble shoot that IC?

Any tips on which transistors I should test? All, just some?

Aside from the caps that I outlined in my image above, I've swapped the majority on the chassis already. Should I go ahead and change out the ones I skipped?

Thanks,
Bill

[grantspain]

i don't have the faintest idea of how to test the ic,i normally just swap them out if i consider they are bad
the fault you have is down to either the vertical ic,a leaky transistor in the vert circuit(401402,403,404)
like i said i have not had this fault so its all guess work
this is more ken,qrz or rickn area of expertise