Nanao MS8-26SU

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thxkbye
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Nanao MS8-26SU

Post by thxkbye » July 9th, 2019, 7:43 am

Please bare with me while I tell this story : (

So I busted the "bright" pot on my MS8 recently and could not repair it. So I ordered a pot from Arcade Parts and Repair that was recommended to me by peter and a cap kit.

I gave the board a wash as it was rather filthy before I replaced the pot and let it dry for several days. Then I replaced the pot and plugged everything back in, turned it on and realized I forgot to plug in the flyback cup to the back of the monitor! I plugged it in and the screen fired on but adjusting the new bright pot adjusted the screen but I no longer got a picture. When I went to adjust the screen pot I heard a whining sound and then blew the fuse in F901. So I decided to do a full recap at this point and the chassis continues to blow F901. Any thoughts?

Thank so much, i would really like to figure this out on my own. But if need be I will send it out for repair. Let me know if you have any recommendations. Been lurking here for awhile, and I appreciate all of your support! I posted this on arcade controls as well but havent heard back yet. Thanks.

thxkbye
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Re: Nanao MS8-26SU

Post by thxkbye » July 9th, 2019, 7:43 am

I was able to test the D1880 and C3306 and both seem to be ok using the instructions below. The values were not all exact as what are mentioned below but pretty close... everything needing to show OL showed OL. Would the flyback go before these transistors? I don't see any evidence of any damage on the board, and I already performed a full recap and i keep blowing fuse F901. Thank you.

Take those transistors out of the circuit , with the DMM set for diode measuring and the following values are what I read from my known good transistors
Q901:
Red test lead to B,black to C: .499
============B,===== E: .536
Black test lead to B,red to C: OL
============ B, ==== E: OL
Red test lead to C,black to E: OL
Black test lead to C,red to E: OL
Q533:
Red test lead to B,black to C:.452
=========== B,====== E:.027
Black test lead to B,red to C: OL
============ B,===== E:.027
Red test lead to C,red to E:OL
Black test lead to C,red to E:.464
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grantspain
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Re: Nanao MS8-26SU

Post by grantspain » July 9th, 2019, 10:46 am

the regulator or bridge are the only things i have ever had blow the psu section mains fuse, I would double check your cap values and polarity
transistors look correct readings
it has to be something you have done and the HT cap being off could have arced and killed the custom sync module, hence why no picture but you had brightness control- then you replaced the caps thinking this would fix it but it won't and in the process you have bridged a track or put a cap in wrong
i know the cap kits had wrong values in them, two in particular but i am not sure if the suppliers rectified this issue- this would not cause a fuse to blow but was more to do with an issue on power up

thxkbye
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Re: Nanao MS8-26SU

Post by thxkbye » July 9th, 2019, 7:23 pm

As you can tell i'm a total greenie at this, but trying to learn. Where are the "regulator or bridge" located? Is there a way to test? I appreciate the help! I ordered my cap kit from peter at arcade parts and repair, hopefully the values are correct i can go back and check. Fuse was blowing before the cap kit though. Thanks

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Re: Nanao MS8-26SU

Post by grantspain » July 9th, 2019, 9:49 pm

2sc3306 is the regulator and you have already tested that and from what i can see its reading fine
bridge rectifier is BD901, read using diode test of course and you would be looking for any dead short

you have chosen a quite complex chassis to repair as a novice and you will find it very challenging, the sync module will be more difficult to fix than your fuse issue

Can you confirm you powered on with the anode cap not located correctly on the tube, if this is the case HV could have flashed over many areas of the chassis and caused multiple problems

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Re: Nanao MS8-26SU

Post by thxkbye » July 11th, 2019, 7:38 am

Yes, it is true. I may just end up sending it off for repair.

I just purchased another chasis, ive always wanted a spare but it doesnt seem to be working either so I may have to swap it our get a refund.

I get no picture whatsoever from a known good pcb or jpac connected to a PC. Screen wont get rid of the raster lines unless its turned all the way down, but the colors all seem bright when adjustable via the front pots, bright, gain, and bias all seem to work well. Any ideas what this could be?

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grantspain
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Re: Nanao MS8-26SU

Post by grantspain » July 11th, 2019, 8:23 am

thats odd normally bright white screen with flyback lines is 200v video b+ missing but you would not get any adjustment from colour cut offs

are you sure your power supply is ok?

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Re: Nanao MS8-26SU

Post by thxkbye » July 11th, 2019, 5:05 pm

I get sound from my known good PCBs... Is it possible the anode cup not being on screwed the PSU? I can take a multimeter and test....

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Re: Nanao MS8-26SU

Post by grantspain » July 11th, 2019, 5:10 pm

doubtful it would kill the psu, worth checking voltages anyway

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Re: Nanao MS8-26SU

Post by thxkbye » July 11th, 2019, 5:19 pm

Here is a video that might help?


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grantspain
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Re: Nanao MS8-26SU

Post by grantspain » July 11th, 2019, 9:22 pm

not using a pc on that are you?

thxkbye
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Re: Nanao MS8-26SU

Post by thxkbye » July 11th, 2019, 9:48 pm

I have a PC with crt emudruver. But this video is connected to a street fighter jamma PCB.

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grantspain
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Re: Nanao MS8-26SU

Post by grantspain » July 11th, 2019, 11:35 pm

i think your sync custom module is the issue
i have been informed the ms8-26 is not keen on signals from pc setups, apparently it can kill the sync module- not experienced this myself but it comes from a solid source

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Re: Nanao MS8-26SU

Post by thxkbye » July 12th, 2019, 1:19 am

This new chassis has never been connected to my JPAC or PC. Should not be an issue anyway because it outputs only in 15Khz, even at post.

Is there anything that I can test to sort this out, between these two chassis i hope to get it to work.

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Re: Nanao MS8-26SU

Post by grantspain » July 12th, 2019, 6:32 am

have you done anything to the rgb wiring?

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