Nanao MS8-26 Issues after recap... [vertical collapse] [SOLVED]

[MagicianLord77]

Hi guys, I'm having some weird issues with the Nanao MS8-26 monitor from one of my two Sega Aero City cabinets, they were brought kind of "as-is" so I don't know its previous background or have any warranty, just to put things a bit in context, what I can tell is:

-When I got the cabinet home just some days ago it was working just fine as it should.
-3 Days after (where I used it 1 hour max in total), the monitor didn't want to turn on!, when turning on the machine sound from the game came out but no image or anything in the screen, not even the usual hi-pitched sound CRTs produce when on.
-But the day after that it did power on! just doing a weird thing the first 30seconds after turning it on (would like to know if there is a proper name for it), and then works kind of okay. That is how it currently works

Video about weird thing it does: https://imgur.com/a/MxNGJnF
Just when I stopped recording, the image from the monitor stopped rolling.
Screenshot of that video (Ignore the ceiling reflection):

Does anybody know what is the name of the rolling image with lines issue? And why it does self correct 30 secs after power on?
Also what should I do if the monitor tomorrow decides not to turn on just like yesterday?

Appreciate any input about this, thank you!

Notes: I am owing cleaning and changing the capacitors of the monitor, does somebody know where I can source a list of them? Also have no experience disconnecting that CRT suction cup to separate the chassis, I am a digital "low voltage" electronics guy, but nobody's gonna repair the monitor for me so I must overcome my fears lol and dive into new depths of knowledge

Note2: I am very suspicious that some guy from the auction house "repaired" or did something to the arcade the day prior to the auction, because they told me it wasn't going to be auctioned because it wasn't working and they were going to repair it, but the day after that it was advertised as working and was auctioned, so that gives me a bad feeling.

 

[nem]

You have a vertically rolling picture with foldover.

Most MS8-26 issues can be fixed with new electrolytic caps and reflowing solder joints. It's a crazy well built chassis. Do you have a 26SG or a 29SE? Take a pic of the chassis if you're not sure.

The chassis is not auto-discharging, so make sure to manually discharge. Leave whatever tool you're using to discharge (screwdriver, etc) in the anode hole for at least 10 seconds, so you can be sure the tube will not have any residual charge left.

 

[MagicianLord77]

Thank you for the advice nem!, it is a MS8-26SG, I will replace its capacitors then, but before I order just that, I want to inspect its PCBs well to see if I can spot another component to be replaced and add it to the order that takes some time to come,..

But, I chose not to start the "monitor inspection round" with that one, it was more convenient to first take off the monitor of the other cabinet I have that is an aero city with a Nanao MS8-26SG too, it's working pretty well, but I understand that I should do a good cleaning and recap anyways, so I took it out and snapped some pictures attached to share and to ask some questions too..

Q1. I see the suction cup has silicone around it, when I get to discharge the tube and stick the cup off, I suppose I should remove the silicone because is something not normal is it? and what should I use to stick it back when I put the cup back on the tube?

Q2. Comparing this monitor with the other same-model one, I see this one has much less black coating than the other one (side pic), is the lack of black paint bad for the monitor? Is this the aquadag? Should I buy some and paint it?

Thanks!

 

[nem]

Your chassis looks good to me! Replace the electrolytic caps and go over the solder joints. For instance you have cracked joints on the neck connector on the neck board. Look for similar ones on the chassis.

Q1. I see the suction cup has silicone around it, when I get to discharge the tube and stick the cup off, I suppose I should remove the silicone because is something not normal is it? and what should I use to stick it back when I put the cup back on the tube?

The silicone is there to make a better seal around the anode cap and the glass around the anode. It's there to stop the anode from arcing. However, unless you have your cab in a really humid environment, I don't feel it is needed. I just clean the old silicone off. Make sure the anode hole doesn't have any debris in it. You can blow it out with compressed air.

Q2. Comparing this monitor with the other same-model one, I see this one has much less black coating than the other one (side pic), is the lack of black paint bad for the monitor? Is this the aquadag? Should I buy some and paint it?

Different tubes have different areas covered with aquadag coating. The one that has less coating is perfectly fine. It came like that from the factory. As long as the dag wire (the braided ground wire) is making contact with it, it's going to be fine.

 

[MagicianLord77]

Hi nem! Thanks for sharing your knowledge, I finally gave the monitor some service:

-Disconnected and cleaned it all with with compressed air and a brush (no washing)
-Recapped the board and neck board with the kit from arcadepartsandrepair, all capacitors matched fine and some new were with greater voltage so, good.
-Took out the solder (with solder sucker) from those cracked joints from the neck board connector and soldered them nicely with new solder
-Found some other cold joints around from transistors or wires soldered to the board, did the process with those too

Seemed like there was nothing left to do so I connected all to the tube back again, and put the monitor over a table next to the cabinet for testing before inserting the monitor inside it.
Turned it on, and found it was sharper than before!, colors were all weird but looked like a magnetization issue, nothing that a demag can't fix, but before that, I started adjusting the screen size and position, and just after it was looking kind of good, boom, a vertical collapse happened (horizontal line on screen), but not an absolute one, the line is there but it kind of vibrates sometimes.

-So I proceeded to spray some contact cleaner on the front adjustment pots (nothing happened).
-Reflow some more joints around in the pcb, including the front adjustment pots (nothing happened).
-Start poking around with a wooden sushi stick (nothing happened), but when I poked to the IC "HA11423" at the named "IC103" small board, something seemed to happen, not sure, but it looked like the image vibrated a lot more, and for one moment one single frame could be seen.

Also, followed the troubleshooting guide of the service manual (MS8-26SU but same for this MS8-26SG) that recommends checking the voltage that the "IC103" small board receives at its pin #4, it says it has to be 10V but got 10.75V, I am not sure if that is wrong?
Also, if voltage is 10V it says to measure pin #7 from the IC103, you should get kind of a square wave from 0 to 2.3v, measured that with my small scope and found nothing, no wave at all, just a constant 0.7v when on.

So, I'm kind of lost because I am not sure what is the priority, it could be:
-Reflowing everything I see on the pcb just because.
-Finding a replacement "HA11423" and replacing it on its "IC103" board, why should it be broke though?
-Replacing every crusty resistor or solid capacitor I see on the board just because? check attached pic.
-???

But the thing that most messes with my head is why had this to happen when I only replaced the capacitors? and why was it working fine for 2minutes??

Thanks to anybody who reads this, and appreciate any input

 

[nem]

You got a full sized frame when poking the small PCB? Sounds to me like you have a poor solder joint still somewhere there. Check the joints on the bottom of the small PCB too. You can have a lifted pad too that can be hard to spot.

The resistors and poly caps look fine to me.

 

[MagicianLord77]

You got a full sized frame when poking the small PCB? Sounds to me like you have a poor solder joint still somewhere there. Check the joints on the bottom of the small PCB too. You can have a lifted pad too that can be hard to spot.

The resistors and poly caps look fine to me.

Maybe the frame wasn't that full sized.., couldn't find any other cold joints, so I took the small PCB out, took out its caps and measured them, and they were fine, soldered the small board back in and got the same issue.
Also I reflowed all pots.

Now I'm thinking about replacing the HA11423 how often do they fail?, if you want to see the issue in acton, here is a video: https://imgur.com/a/Tt8w8xf (Monitor is vertical, running pacmania)

Thanks!

 

[nem]

That's weird. I haven't seen that before.

You could try asking grantspain on Arcade-Otaku. He's probably fixed dozens of these.

 

[Mukuro_W]

You have to replace c433, r433, r436, q401, q402 and c437, plus you have to check for broken or cold solder joints just under q402 and q401 this is an hot area look also for broken traces.
Q401 and q402 are both D1138 transistors, r433 2.2k 1/4w, r436 15k 1/4w c433 10uf 50v .

 

[MagicianLord77]

You have to replace c433, r433, r436, q401, q402 and c437, plus you have to check for broken or cold solder joints just under q402 and q401 this is an hot area look also for broken traces.
Q401 and q402 are both D1138 transistors, r433 2.2k 1/4w, r436 15k 1/4w c433 10uf 50v .

Thanks, so far I took out q401 and q402 (pretty difficult because they are tightly screwed in), measured them with a "lcr-t4 ic tester", one gave hFE=123 / Uf=600mV , the other hFE=108 / Uf=600mV so we can say they are good right? I would replace them anyways but still haven't found where to buy them locally.. still looking

Also took out and measured r433 and r436, both are tiny like if they were 1/8w, a bit crusty but they give the right values, I won't put them back, I'll get replacements anyway, can they be blue metal film resistors or they have to be carbon ones? cause I've got plenty of the metal ones..

c433 and c437 were recently replaced with nichicon parts from the capacitor kit so they should be good, but I will test them soon..

 

[Mukuro_W]

Use metal blue ones, those are just better than carbon resistors.

 

[MagicianLord77]

Quick update

-I've been taking out lots of resistors from the vertical oscillation circuit, also some power resistors that seemed to work hot, and replacing them with bigger wattage versions (1/2w replace with 1w).
-Also managed to source a HA11423 IC locally, took out the original IC, soldered a dip socket just in case and put the new one in there.
-Desoldered and measured the TLP521-2 (octocoupler), seems to work fine, anyways put a socket too and put it back in
-Desoldered and measured Q451 Q452 Q453 and Q534, all nice
-Cleaned some trimpots from inside like the V-LIN and S.P.C (side pincushion correction), the S.P.C. was giving like 1.3kohm resistance between some pins but after contact-cleaning and wiggling it now it gives 17hm, like it should.

After all this work, connected everything back in and, it still works exactly the same, could've been worse because after unsoldering and soldering some pads lifted and had to jump them, but, that, it's still the same.

Now I'm starting to think about measuring the input oscillation signal from where it originates and find where it dissapears(? I've got this cheap oscilloscope that can be useful, but I'm a little worried about connecting it to a high voltage point and frying it

 

[Mukuro_W]

Sorry for delay, you should replace the two D1138 even if they test aparently good, also when work on ms8 26 pay attention when you are on vertical deflection area because it will be all the way cooked and all traces so fragile

 

[MagicianLord77]

Sorry for delay, you should replace the two D1138 even if they test aparently good, also when work on ms8 26 pay attention when you are on vertical deflection area because it will be all the way cooked and all traces so fragile

Thanks, in the end the problem was at the vertical deflection area indeed, but wasn't those transistors, the part which was causing all this issue was ZD431 (24v 0.5w zener), the one next to r430 at pin#7 of the IC103. It didn't seem physically faulty, but after taking it out (random components measuring), measuring with a multimeter gave around 300ohm resistance between its legs on both ways! that's very bad. Replaced it, and got a perfect vertical deflection going on, it now works as it should, with no weird vibrations or anything.

Thank you nem for suggesting posting this at the other forum!, grantspain was there and gave me some tips.

I've put this on the other forum too, but I'd like to know your opinion too, this is an easy one, setting up the SCREEN flyback pot, I should turn on the monitor without signal, front brightness pot to minimum, and set the screen flyback pot to just after the raster lines disappear right? Thank you!

 

[nem]

Excellent, well done!

I've put this on the other forum too, but I'd like to know your opinion too, this is an easy one, setting up the SCREEN flyback pot, I should turn on the monitor without signal, front brightness pot to minimum, and set the screen flyback pot to just after the raster lines disappear right? Thank you!

You want to set the B+ voltage without it being connected to anything.

As for calibrating it, personally with a MS8-26 I boot up a test menu or anything with a black background, set everything to the middle position (brightness, gains, cutoffs) then turn the screen pot until the raster starts showing in the background. Then go to a color bar screen and adjust the cutoffs and gains. Unlike almost all other monitors on a MS8 adjusting cutoffs will offset the gains and vice versa, so you'll have find the correct balance. Remember to adjust the focus pot at the end. Ultimately, you should have a really good looking image with this monitor!

 

[MagicianLord77]

Excellent, well done!



You want to set the B+ voltage without it being connected to anything.

As for calibrating it, personally with a MS8-26 I boot up a test menu or anything with a black background, set everything to the middle position (brightness, gains, cutoffs) then turn the screen pot until the raster starts showing in the background. Then go to a color bar screen and adjust the cutoffs and gains. Unlike almost all other monitors on a MS8 adjusting cutoffs will offset the gains and vice versa, so you'll have find the correct balance. Remember to adjust the focus pot at the end. Ultimately, you should have a really good looking image with this monitor!

Perfect! Thanks! It had a 94.0V B+ Voltage, turned it down to 91.9V, (service manual says 92.0+-0.52v), then did your procedure, good to know that the cutoffs offset the gains, it's tricky to get it right indeed, now got a really nice looking image, and have put the monitor back into the cabinet, it is really enjoyable to play with it now

 

[Mrhide]

looks like I'm going to be trying a few things from this thread :

That's before _and_ after a capkit.

Doing the kit, I saw this cooked R433 and knew I would have to go back ....

edit: I popped that R433 out and it's a dead short.. no resistance whatsoever.

 

[Mrhide]

... and popping a 3.3k 1/4w resistor in there (it's supposed to be a r433 2.2k 1/4w but I needed to get this working NOW), I get something much better