Repairing MS8-29FSG

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hindered
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Repairing MS8-29FSG

Postby hindered » December 29th, 2015, 3:45 am

Hey guys, I've been a member here for some time but don't post often (ever?), but I'm a regular over on KLOV. Since this forum is definitely more about candy cabinets, I've decided to document this problem/repair here in the hopes of getting more help / potentially helping more people in the future.

I have an Astro City that I've had for ~5 years with a Nanao MS8-29FSG (Grantspain thought it was a MS8-29SU but everything I can find indicates it's a FSG, and jomac doesn't list a 29SU that I can find). EDIT: it is a SU, never doubt Grantspain :).

Sometimes, there was noticeable whine from (I assume) the flyback while playing games.

Last week, I was playing Die Hard Arcade on a new (to me) STV board and exactly as I beat the game, the monitor immediately wigged out on me. The screen shrunk to about 1/3 to 1/2 the original width and was white/fuzzy. There was no discernible color/picture, but the game was still playing blind.

To make sure it wasn't the PCB (it was my first time testing the STV main board), I swapped it out for a SVC Chaos. Same problem. However, as I was fiddling with the dials a bit, I heard the monitor whine a little bit and snap into a perfect picture again. But within 60 seconds, it had died again. Sometimes, by turning the horizontal size pot all the way to one way or the other (can't remember if it was full open or full closed), the picture would snap back in again for a little bit, and then fade out again. After dialing the pots some more, this is the best I was able to get the monitor to look (which is way better than it looked during the initial failure -- you can at least tell that it's trying to display the game somewhat). https://www.youtube.com/watch?v=DrPcA_mXUqk

Grantspain indicated that he believed was probably just an issue with caps, and I've done 10 or so cap kits before, so I ordered a cap kit for a MS8-29FSG on ebay, which arrived today. I've also ordered a desoldering station to replace my gets-way-too-hot-and-lifts-traces squeeze bulb iron, and it'll be here Wednesday.

Unfortunately, I've got a broken ankle, so I'm not able to remove the whole tube easily from the cab (and I don't have a test bench area anyway -- maybe this will be my motivation to set one up). So, I discharged/removed the anode cup, discharged the filter cap, removed the neckboard from the tube, removed the black wire from the neckboard (hv ground??) and disconnected the power, degaussing coil from the chassis. I also disconnected the ribbon cables to the remote adjustment board. Then, laying on my back, I was able to undo four screws that mount the chassis frame to the tube frame. From there, it was a matter of undoing 6-7 screws and cutting a glob of white glue to get the chassis free of the plastic and metal frames.

After taking out the chassis, I did some spot checking and all the caps seem to line up appropriately with the FSG cap kit. However, the cap kit did not include the cap for the neckboard, which is a bummer. I've got a small supply of caps on hand, so hopefully I've got one of that value. It also didn't include the filter cap, probably for cost reasons. I'm pretty sure they rarely go bad anyway.

So, upon visual inspection, I don't see anything obviously wrong with any of the components, no bulging caps or burned resistors. However, this area looks a bit crispy.
Toasty Area.JPG
This shows the slightly crispy area of the main board.
Is this cause for concern?

Also, another thing I found during inspection, is this non-original pot. I have a vague memory of making this fix when I first got the cabinet because the original pot had disintegrated.
Swapped Pot.JPG
Non-original pot in VR432.
Is this the right value pot for VR432?

Also, there are some bad/cold solder joints on the neckboard and the chassis, I plan to clean those up as I do the cap kit. Also, I've found cap lists for this board and descriptions of the locations, but if I'm feeling motivated enough I'll try to make an actual cap map image.

Is there a schematic for this monitor? I'm guessing no...

Thanks for reading (sorry I'm so long winded -- I like to be thorough!), and thanks for any guidance you can give me.
Last edited by hindered on March 9th, 2017, 4:32 am, edited 2 times in total.
nikolash
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Re: Repairing MS8-29FSG

Postby nikolash » December 29th, 2015, 7:56 am

I think it's a capacitor issue, try freeze spray on capacitors to see if it fix picture, and you should find which one is faulty.
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nem
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Re: Repairing MS8-29FSG

Postby nem » December 29th, 2015, 11:01 am

hindered wrote:However, this area looks a bit crispy. [pic snip] Is this cause for concern?


I have three of these same monitors, all of them look the same in that area. I guess it can run quite hot.

Anyway, all three also exhibited various issues (two wouldn't sync at all, one had wavey lines going across the image). Two of them I fixed just by changing the caps and reflowing dodgy looking solder joints.

An ESR meter is a god send if you don't want to go through the ordeal of changing every single cap.
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hindered
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Re: Repairing MS8-29SU

Postby hindered » December 29th, 2015, 1:39 pm

nikolash wrote:I think it's a capacitor issue, try freeze spray on capacitors to see if it fix picture, and you should find which one is faulty.


I think you're probably right. Unfortunately, I can't test in this way since my cab/monitor are completely disassembled, and I don't have a setup that allows me easy access to the chassis while the monitor is powered on.

nem wrote:
hindered wrote:However, this area looks a bit crispy. [pic snip] Is this cause for concern?


I have three of these same monitors, all of them look the same in that area. I guess it can run quite hot.

Anyway, all three also exhibited various issues (two wouldn't sync at all, one had wavey lines going across the image). Two of them I fixed just by changing the caps and reflowing dodgy looking solder joints.

An ESR meter is a god send if you don't want to go through the ordeal of changing every single cap.


Re: The crispy area -- that is good to know, thanks. I won't concern myself with it.

Re: The ESR, yeah I've been thinking of picking one up that tests in-circuit! I typically just change out all the caps on older (1980s) monitors and was planning to do the same on this one. Maybe it's a bit wasteful? I tend to look at it as "preventative maintenance" though.
Last edited by hindered on January 4th, 2016, 4:38 pm, edited 1 time in total.
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nem
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Re: Repairing MS8-29FSG

Postby nem » December 29th, 2015, 2:07 pm

Oh, absolutely. It's wise to change to all of them at once. I'm just lazy!
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hindered
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Re: Repairing MS8-29SU

Postby hindered » December 30th, 2015, 9:59 pm

What's the polarity of c446 pictured here? There's no polarity on part of solder side.
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Last edited by hindered on January 4th, 2016, 4:37 pm, edited 1 time in total.
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Re: Repairing MS8-29SU

Postby hindered » December 30th, 2015, 10:03 pm

Google says its non polarized which makes sense. The cap kit contained a polarized cap. Can I use it? Google is saying no...

Grantspain, if you see this, did you truly mean 29SU? Since I could find no information about the 29SU, and the cap list for 29FSG seemed to match my cap needs, I ordered the FSG kit. I had assumed you accidentally mixed it up with the MS8-26SU but maybe that's not the case?

Edit: I should have known better than to doubt Grantspain -- the cap kit seller agrees it was probably the 29SU. My fault for ordering the wrong kit.

Double edit: the seller is graciously sending me a non polarized cap.
Last edited by hindered on January 4th, 2016, 4:37 pm, edited 1 time in total.
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Re: Repairing MS8-29SU

Postby hindered » January 4th, 2016, 2:16 am

Can somebody please walk me though checking/adjusting the b+ on this chassis post cap-kit? What is the test point? Where do I hook up my negative lead? What should the voltage be? What dial do I use to adjust it?

EDIT: Searching for different terms, I found this post by grantspain: viewtopic.php?t=29627

I'm gathering the b+ should be ~94v, and I can use the two sides of fuse 902 as my +/- connection. I think the only question is which pot to use to adjust it, if necessary. I did find a small pot labeled b+ which is glued from the factory. I'm assuming this is the one, or does the brightness knob on the flyback adjust b+/make more sense? I think that's the case for some monitors (could be misremembering, it's been a long time since I've worked on a monitor), but maybe it's not the case for this one. My gut is telling me I will need to tweak the small pot on the main PCB labelled B+.

Double Edit: This topic is now the #1 search result for MS8-29SU, which shows how little information there is on this monitor...
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hindered
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Re: Repairing MS8-29SU

Postby hindered » January 4th, 2016, 8:15 pm

Last two caps arrived today! Looking forward to buttoning this one back up!
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Re: Repairing MS8-29SU

Postby grantspain » January 4th, 2016, 10:05 pm

you should not need to adjust the b+ once the cap kit is done
94v sounds correct,read at fuse 902 and a capacitor negative
pot is marked b+ on chassis

dry solder joints are common on these chassis,in particular all the coils and transformers plus that crispy area you mentioned
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Re: Repairing MS8-29SU

Postby PunkicCyborg » January 4th, 2016, 10:16 pm

I had the same issue with mine, recapped and reflowed the bad solder joints by the areas that got hot then it collapsed a couple days later. Replaced the Vertical Hold IC and it fixed er up again. About a year later the screen was kind of funky again and wobbled a bit when people were playing fighting games and stuff and after touching the pots in the remote board it caused the same issue. I cleaned them all up with contact cleaner and all is good. Good luck with your repairs
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Re: Repairing MS8-29SU

Postby hindered » January 10th, 2016, 5:53 pm

Well, the last two caps arrived during the week, and yesterday I put them in. I also spent some time desoldering/resoldering sketchy looking areas of the chassis and neckboard.

Today, I put it all together again. I reconnected the remote board, connected the power to the side of the monitor, connected the yoke wires, the degauss wires, the black wire to the neckboard, the anode wire into the hole in the tube, and the neckboard to the tube pins. When I powered it on, there was a "fsssSSSSSSZAP" noise and I immediately turned it off. My first thought was that maybe I didn't get the anode wire fully in the tube, but when I checked, it seemed snugly in there and I was unable to easily remove it. I asked my wife to come downstairs and turn the unit on, so I could see what happens, but the monitor was 100% non responsive.

I'm pretty sure I've at least blown a fuse. Does anyone have any idea what's going on? My mind tends to jump to things like backwards caps, but I double checked them as I put them in. I am confident (but not certain) I did them all properly.

One other thing that comes to mind -- When I was resoldering the neckboard, the big white resistor fell out after I removed the existing solder. I'm 99% sure I put it back in the same way, but it's possible I didn't. I also don't think that part has polarity, in any case. Could this potentially be the problem?

At this point, I'm ready to admit defeat, at least until my leg heals and I'm able to remove the monitor and tube entirely for ease of troubleshooting... Unless somebody has any ideas...
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Re: Repairing MS8-29SU

Postby grantspain » January 10th, 2016, 6:34 pm

sounds like a fuse blown
wrong polarity cap would have exploded
resistors are not polarised

wait until your leg is better
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hindered
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Re: Repairing MS8-29SU

Postby hindered » January 10th, 2016, 7:09 pm

grantspain wrote:sounds like a fuse blown
wrong polarity cap would have exploded
resistors are not polarised

wait until your leg is better


But a blown fuse is a sign of another problem, right? It's possible one of the caps exploded, I don't have visibility to all of the board when it's installed.

Blah.
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Re: Repairing MS8-29SU

Postby grantspain » January 10th, 2016, 8:46 pm

yeah blown fuse means dead short somewhere
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Re: Repairing MS8-29SU

Postby hindered » January 10th, 2016, 10:57 pm

grantspain wrote:yeah blown fuse means dead short somewhere


Hmm ok. The first cap I removed had a lifted pad so I bent the leg over to connect to the next component in line and soldered it together. I'll have to double check that when I am able to get to this again.
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Re: Repairing MS8-29SU

Postby hindered » January 12th, 2016, 5:22 pm

Just thinking about it, could this behavior be caused by a cap with the wrong uf value? I double checked most values as I replaced them but don't remember 100% checking every cap as I replaced it. Since my cap kit was intended for a FSG, it's possible a few of the caps were different, right? The only differences I found were the NP cap and the neck board cap, though.

I hate it when things don't work. :)
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hindered
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Re: Repairing MS8-29SU

Postby hindered » March 3rd, 2017, 5:04 am

I finally am hoping to get around to fixing this issue. My leg is back to near 100% and I have the strength to tackle things like this properly.

Wish me luck. :) I plan to start by checking for shorts like grant recommended.
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Re: Repairing MS8-29SU

Postby hindered » March 5th, 2017, 8:28 pm

OK, so I managed to make some progress on this today. Got the monitor out and set up in my workshop so I can troubleshoot with the monitor out of the cabinet per grantspain's recommendation. I did a visual inspection of the board and found no blown or bulging caps or burned resistors. The 125v 3A fuse at F901 looks and meters good. THe 125v 2A fuse at F902 is very visibly blown.

MS8-29SU F902 Blown.JPG
MS8-29SU Fuse F902 Blown


Per grantspain's advice here (viewtopic.php?t=572), when fuse 902 blows, you should check Q901, BD901, NTH901, PTH901. I'm not sure which component Q901 is, the number was on the edge of the board with an arrow pointing inwards, kind of towards Q902. Pin 3 of BD901 is very close to C903 so I metered them and got continuity. Should there be continuity here? I don't see a visible solder bridge and it's not possible to tell if there is a trace connecting the two as they are so close to one another.

I also checked the legs of the daughter boards for continuity, and I did find one thing that was suspect. IC103 had continuity on pins 5 and 6. From looking at the traces, I don't think I expect them to have continuity.

hindered wrote:
grantspain wrote:yeah blown fuse means dead short somewhere


Hmm ok. The first cap I removed had a lifted pad so I bent the leg over to connect to the next component in line and soldered it together. I'll have to double check that when I am able to get to this again.


I checked this specifically. I must've lifted a pad when desoldering C560, so I bridged it to R560. Doublechecking it today, it looks fine.

So, I"m at a loss for what to do next, especially without a service manual for this chassis. Can somebody point me in the right direction, and help me "check" Q901, BD901, NTH901, and PTH901? I do not know how to check these parts beyond the basic metering I've already done. If it helps, in addition to a multimeter and other basic tools I also have an ESR meter for capacitors that works with the caps still in the board.
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hindered
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Re: Repairing MS8-29SU

Postby hindered » March 8th, 2017, 12:36 am

Here are some pictures of the chassis and the label on the monitor tube. I'm wondering still -- do I really have a MS8-29FSG and not a MS8-29SU? Grantspain convinced me it was the SU last year, but I can't find the message that explained his reasoning. Here are some pictures to hopefully 100% identify the monitor.

MS8-29 FSG Label.JPG
MS8-29 FSG Label

MS8-29 XXX Chassis Parts Side.JPG
MS8-29 XXX Chassis Parts Side

MS8-29 XXX Chassis Solder Side.JPG
MS8-29 XXX Chassis Solder Side


If this really is a FSG, then I have a bad feeling about the non polarized cap I put in at C446 (see previous posts). According to the cap map here (http://wiki.arcadeotaku.com/w/Nanao_MS8-29FSG) C446 should be 33 uf @ 16v, assuming polarized. Using a non-polarized cap in place of a polarized cap would surely blow a fuse, right?

EDIT: Comparing to Jomac's site at http://www.jomac.net.au/wp-content/uplo ... -29FSG.jpg my motherboard looks 100% like a MS8-29FSG.
Last edited by hindered on March 9th, 2017, 4:34 am, edited 1 time in total.

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