(Topic ID: 287223)

MPU-35 missing upper left side parts

By emsrph

9 months ago


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  • 11 posts
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  • Latest reply 9 months ago by mad_carl
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#1 9 months ago

Picked up a 2518-35 MPU generously provided by Kwaheltrut

I will try to bring this back to life. Has some typical corrosion area that needs neutralized and parts replaced. Also has components missing from the upper left of the board.

Just wondering if the missing components from that area indicate a particular problem that I’ll also need to address.

Other info- U10 and U11 sockets replaced. Jumpered for U2 and U6 2532 or 9332. From the E-570-52 chip seems to be from an Eight Ball Deluxe, Embryon, or Fireball II

Thanks

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#2 9 months ago

If I am reading this right those are tied into the BCD information sent to the displays. So none of your score displays would work without that section

https://www.ipdb.org/files/476/Centaur_Sh_matics.pdf

#3 9 months ago

Thanks Cheddar I’ll check out the schematic.

I guess part of my question is what other problem might this board have that would require those parts to be removed? There is no corrosion up there.

#4 9 months ago

just one of those things with pinball where you wonder why?

but yes they will need replacing and looking at the reset section, that R11 82ohm looks cooked.
i'd be replacing that and personally, when i do i raise it up at least an inch to keep the heat away from the nearby components.
also I use a 3 watt.

#5 9 months ago
Quoted from Rikoshay:

just one of those things with pinball where you wonder why?
but yes they will need replacing and looking at the reset section, that R11 82ohm looks cooked.
i'd be replacing that and personally, when i do i raise it up at least an inch to keep the heat away from the nearby components.
also I use a 3 watt.

Maybe it was desoldering practice on a non booting board. Done neatly. Looks like no damage to traces or thru holes.

Good suggestions on the big resistor. The whole reset section will need replaced (after removing corrosion). Did that before on a board that was constantly rebooting but the board was clean to start.

#6 9 months ago

good luck, not that you'll need it, you sound competent enough

it's the joy and satisfaction of stripping down a non working board and bringing it back to life, a nice sense of accomplishment.

a little off topic, but having done what your about to do, and having seen boards where battery corrosion hasn't been done properly, once restored I put a water based floor clear on the front of the board, applied with a small hobby type paint brush, just to seal it.
should a component need replacing it's still easy to 'break' through the clear if need be, but keeps it protected.

#7 9 months ago

With no battery damage to the upper corner I can't imagine why they would remove those components. How does that corner look on the back side. Since you are missing resistors and caps you are only out a dollar or so in parts for that section.

#8 9 months ago

EPROM "838-13" at U2 is Eight Ball Deluxe

#9 9 months ago

Thanks Quench, good eye. With what I saw at U6 Eight Ball Deluxe was one of the three possibilities.

What other kind of sealers do people use after corrosion removal? I read clear nail polish?

Here’s the back. Not bad.

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#10 9 months ago

I only suggested a water base floor clear for a sealer due to ease of application.

I use nail polish on the rear of boards where a jumper has had to be installed, helps keep it in place.
I find nail polish dries quite quickly and may not give you a uniform finish for the front.

#11 9 months ago

Here’s my guess.

Someone was testing/ touching the displays...display wasn’t in the bracket all the way and it popped out and shorted to the metal housing on the solder side of the pcb.

I only say this because this happened to me haha

I was told that section of the mpu probably ate shit but I ended up just replacing the mpu. Still have the old mpu on a shelf, haven’t gotten around trying to fix it.

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