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Help identifying a coil on Nanao MS9 board

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grimdoomer

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I have a Nanao MS9 board I pulled off the CRT in an Astro City cabinet that I am trying to repair. There is some sort of coil at position L504 that is falling apart and I want to replace it, but I haven't been able to find anything online based on the part number "623A1 R". I found some old service manuals for similar MS9 boards that list it as "coil" with a manufacturer part number of 05fl6623AI or 08N46396AI, but I haven't been able to find anything based on those numbers either. I attached a picture of the coil and where it was located on the board. Does anyone know of a replacement part I can use for this? Or how I could identify enough info on the coil to source a replacement part for it? Any help is appreciated!

IMG_4862.jpgIMG_4861.jpg
 
L is for inductor. My best guess is a filter inductor of some kind.
 
This is what appears in the manual for Coil L504:


coil-L504.jpeg


EDIT: I see you already look at it on the manual... Unfortunately, there is no additional info for that...
 
Yup that's the exact manual I was looking at. Those secondary numbers I assume are something you could get from the manufacturer of the arcade cabinet the manual was for, but fat chance of that happening now.

I tried to look up how I could measure the inductance of this thing but couldn't find a reliable procedure that didn't involve equipment I don't have (like an oscilloscope). FWIW the inductor doesn't seem bad as I can measure ~1.1Ohm resistance across it. So maybe I just put some heat shrink tube over it and call it a day? I need to wait for my cap kit to show up so I can do a better diagnosis of what's wrong with this monitor. The inductor just stood out since the casing was falling apart.
 
So I ended up just wrapping the coil with shrink tube and putting it back in. I finished replacing all capacitors except for C911 (the big on the primary side) since it's on order atm. I connected everything back up but the monitor still does not turn on. I checked B+ voltage and was getting 0v. I took the board back out and connected it to A/C power on the bench so I could troubleshoot.

I checked I had 120V A/C going into the rectifier at BD901, and it seems to only be putting out ~68V DC when the manual says it should be 75V. Not sure if that is a problem or not. Next I checked the big cap at C911 (while it was off the board) for capacitance and get ~875uF when it should be closer to 1000uF. I have a new one on the way but wanted to do diagnosis in the mean time in case I need to order more parts. Lastly I checked the transformer at T901, on the primary side I'm getting ~68V DC going in and on the secondary side I'm getting 0V on all pins.

I desoldered the transformer from the board and checked all the windings. None of them appear to be open, and the results I got testing it with a meter reflect what I can see on the ms9 schematic. I can't read anything on the schematic other than that there are two sets of windings on either side, which is what my testing showed. So now what? Could the transformer getting 68V instead of 75V or the big capacitor be causing the transformer to not output anything on the secondary side?
 

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You have pin 2 on the flyback desoldered, so you're dummy loading b+?
 
I have no load on B+, do I need one? FWIW even when I had pin 2 soldered in I still got 0V on B+. The transformer has 2 different windings on the secondary side, so even with no load on the high voltage winding (75/117V) for the flyback I would expect there to be voltage on the low voltage winding, no? Is the low voltage winding only used if the flyback is powered?
 
I put a load on B+ using a 40W light bulb and got nothing, no light and meter reads 0V. If I connect the light to the primary side it lights up and I get a reading. So I guess the transformer is bad? I'm guessing this is a custom built transformer so I'm not going to find a drop in replacement. But it should be possible to adapt a new one to the board if I can figure out what each winding is rated for.

The manual shows the transformer outputting 75V, 24V, 12V, and 6.3V on the secondary side. I know where the 75V one is but I'll have to figure out which are the other three unless anyone happens to know? I assume I'll also need to know the power consumption for each output? Is there anything else I'll need to consider when spec'ing out a new transformer?
 
6.3V will go to pin 4 heater on CN502.

12V will go to pin 1 VCC on LA7837.

24V will go to pin 8 pump up supply voltage on LA7837.

Anyway, I suggest you make a thread about this on the ArcadeOtaku forum. There's two guys there that know the MS9 inside out. Best to ask the experts.
 
Last edited:
Awesome, thanks for the info and recommendation. I'll post what I've found there and see what info I can get.
 
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