Rebuilding a Gameplan MPU-1

[SirPeale]

I'm in the process of repairing a "Foxy Lady" pinball that will be donated to the American Classic Arcade Museum when it's done.

This unit sat in a storage shed for ~20 years until it was "unearthed" recently.

Of course the MPU-1 board has the usual battery damage.

First thing I've done is soak the board in vinegar to neutralize the batter damage.  Then a good rinse and dried in the oven for several hours.

I'm trying to source the DIP switches now...these don't quite look what I'm going for here...

What's a better match on Mouser?

[SirPeale]

I guess it helps if I get the correct mounting type...

[SirPeale]

Anyone?

[ChadTower]

Considering where this game is going to end up worst case is to just hard jump the config...

[SirPeale]

The whole board is bad.  Worst battery damage I've ever seen.  I'm fine with replacing the switches.

I found a bartop board that had a neat trick: socketing the switchbanks.  Switches go bad, just swap them out.  Might try that.

[ChadTower]

Almost all of my spare Berzerk ZPUs have broken switchbanks.  Probably rough handling.

You shouldn't have to socket them.  They rarely change anyway - just get it all cleaned up and put in some new ones.  They won't get hit with that style acid again once you relocate whatever caused that.

[SirPeale]

Sandblasted the board today.  Yes, it's an extreme measure.  Yes, it needed it.

Should have taken a "before" shot.  Didn't.

I've got my work cut out for me.   I was going to try and salvage the non-socketed chips, but they're too difficult to remove without damaging them.  So I'll replace them.

Anyone have a schematic handy?

[lilshawn]

the foxy lady uses a mpu-1 system and they are basically the same..... this is for "chuck-a-luck" most schematics should match.

http://www.ipdb.org/files/3020/Gameplan_model_110_schematics.pdf

[SirPeale]

the foxy lady uses a mpu-1 system and they are basically the same..... this is for "chuck-a-luck" most schematics should match.

http://www.ipdb.org/files/3020/Gameplan_model_110_schematics.pdf

I was just looking at that, but that's not what I'm looking for.  I'm looking for the schematic for the AS-2518-35 that's in it. A couple of the chips I need to replace had the numbers removed when I blasted it, plus a few other parts.  Besides, its a good idea to have it.

[ChadTower]

Should have taken a "before" shot.  Didn't.

A couple of the chips I need to replace had the numbers removed when I blasted it, plus a few other parts. 

Double ouch!   

[SirPeale]

I'm not worried.  It's well documented, I just need the schematic.  I see references to people having it on the 'net but so far haven't found it.  But I've also given it about two minutes of searching.

[lilshawn]

fine, http://arcadearchive.com/pinball/trek/Schematic-MPU%20Module%20AS-2518-35.pdf  



i'm going to bed now.

[SirPeale]

fine, http://arcadearchive.com/pinball/trek/Schematic-MPU%20Module%20AS-2518-35.pdf  



i'm going to bed now.

Muchas gracias!

I've removed two sockets.  Man those things are a pain.  I'm just glad they're in bad shape (as strange as that sounds) as it made the removal process a lot smoother.  Fixing the holes and whatnot should be fun...

[lilshawn]

i find on allot of those old boards, using a dremel with a cutoff wheel to chop the ic's legs off right next to the chip, then using needle nose pliers and the soldering iron to take the stumps out, makes things allot easier....and less likely to rip of a trace because a leg is still semi-attached to the board.

it's easier to do it one at a time than to try and get all 20 at once IMO

[ChadTower]

The dremel throws little metal slivers around.  Be careful there.  It's also a LOT easier to bounce the thing and gouge another part.

[ChadTower]

Actually, I was thinking more along the lines of throwing slivers around the PCB, not into your eye.

But eye injuries are no joke, true enough, I'm recovering from one right now.   

[SirPeale]

i find on allot of those old boards, using a dremel with a cutoff wheel to chop the ic's legs off right next to the chip, then using needle nose pliers and the soldering iron to take the stumps out, makes things allot easier....and less likely to rip of a trace because a leg is still semi-attached to the board.

it's easier to do it one at a time than to try and get all 20 at once IMO

I always do this when removing ICs.  I was just trying to salvage the existing ones.

[ChadTower]

Yeah, we heard you did it on a Burger King christmas card or something.

Nah, I scratched my cornea right before the AFC title game started.  Bad scratch, too.

[lilshawn]

The dremel throws little metal slivers around.  Be careful there.

it does? i usually use a mini cutoff disk (the non-fiberglass re enforced kind.) and get nothing but powder. which i just wash off with a spray of contact cleaner. no big chunks are involved at all.

It's also a LOT easier to bounce the thing and gouge another part.

that usually only happens because your speed is too slow, and your pressing too hard/too fast... causes the end to bind up instead of just cutting through the metal. I don't really need to talk about making sure you hang on to it good n' tight do i?

"let the tool do the work for you" is what my shop teacher used to say....untill he chopped off his fingers...then he became the computer studies teacher...which was okay since i took that too.

what where we talking about?

[SirPeale]

I always do this when removing ICs.  I was just trying to salvage the existing ones.

Not wanting to damage the board further, I invested in a desoldering iron.  An Aoyue 474A+.  It had been recommended on the KLOV repair boards with glowing reviews.  Very reasonably priced unit, so I picked it up.

I wish I'd gotten one years ago.  What would have taken me an hour to remove ONE chip with a sucker and braid took me the same time to do the entire board.  Amazing.  And the pads are so clean and shiny because it sucked up all the gunk.

You'll note the thread title has changed.  I (stupidly) looked at the board and thought "oh hey!  AS-2518-35!" for the sole reason of the battery.  When I pulled up the schematics, of course they're completely different!

The schematics for the MPU-1 are here: http://files.pinball-fixers.com/gameplan/MPU_Schematic_(MPU-1).pdf.  Trying to identify the chip @ U13.  When I removed it from the board nearly all the legs came with it.  All the other chips came off without complaint.

[lilshawn]

coolsville dady-o! 

still trying to drop the hint to get the boss to pick up a de-soldering station for at the shop...the ammount of re-working we end up doing would make it worthwhile...guess for now we will stick with the old solda-pult.

[SirPeale]

It was like $135 shipped.  The money you'll save in time alone makes it worth the purchase price.  If your time is worthless, then this machine is not for you.

Heck, get one just for yourself and use it at the shop.  Once your productivity picks up 1,000,000% he'll see how worthwhile it is.

Do get extra spring filters and sponge filters.  Extra tips wouldn't hurt either - I wore thru one already.

[SirPeale]

I may have to just give up on this particular board.  The battery damage is very great.  So many traces missing.  I think it's even missing a few parts.  Hard to tell - some spots there are legs with nothing there, but often parts would be trimmed out.

There is a forum dedicated to people who restore Gameplan pins, I may ask them for advice.

[SirPeale]

Finally got my shipment from Mouser and started in on repairs.

Rebuilding destroyed traces is such a pain.  Not so bad if there are just a couple, but there are many of them.

And I screwed up on ordering sockets.  I wanted .6" 28 pin sockets, but ordered .3" instead! 

[lilshawn]

you would think that since you are ordering .6 chips in quantity, that they would ask to make sure you wanted .3

oh well....

FOR SALE:......

[SirPeale]

you would think that since you are ordering .6 chips in quantity, that they would ask to make sure you wanted .3

oh well....

FOR SALE:......

I didn't order any chips, but refilled my socket supply.   Since I socketed the entire board (plus a Defender board I've been poking  @) I was nearly out.

No big deal, I've got more stuff to get.

[SirPeale]

Ordering the right parts seems to be a recurrent issue with you..... 

I get 99% of them correct.  When you're entering in a laundry list of them, you're bound to make mistakes.

Tried rebuilding the missing traces today.

[SirPeale]

The edge connector is badly damaged, so I thought I'd employ the Bob Roberts edge connector rebuild trick.

Only problem is finding the connector itself (with the eyelets).  Anyone have a lead?  Preferably on Mouser?

[SirPeale]

Replaced all the 4148 diodes yesterday.  Many of them broke in two when I tried to move them.