Meter disconnected error - please help

[sixcardmark]

Reseat the mpu. If it is not slid in all the way into backplane you will get that error. A bent pin on mpu where it plugs/slides into backplane can also cause it.

[Sunrise Side]

Might have blew a surface mount chip on the MPU. I don't remember the chip position.  Can you see or smell burnt on the MPU? 

[otguy87]

there are a couple of different mobos for the 3902 mpu that you have.
grabbing 2 that i had here they have part numbers of:
pn: 75905300 rev b
pn: 75905701 rev a


there are probably a few more variations


check the side of your MPU that plugs into the mobo and see if any of the pins got bent, that's the easiest and cheapest fix(if its the problem)

Thanks, found it! It is 75905701 rev a.

I will probably buy a backup just in case now. Thanks!

[otguy87]

Reseat the mpu. If it is not slid in all the way into backplane you will get that error. A bent pin on mpu where it plugs/slides into backplane can also cause it.

I have taken it out and back in many times now Give it a nice tug too, but no avail.

I do not see any bent pins either. I will double check though.

I do appreciate the help though! Any advice/suggestions are appreciated

[otguy87]

Might have blew a surface mount chip on the MPU. I don't remember the chip position.  Can you see or smell burnt on the MPU?

I did not smell any burning after the error message. After that message I did take it out again to inspect (with it off this time), but nothing.

When you say mounted chip, do you mean the parts that have like 20 "legs" on them?

[rickhunter]

A surface mounted chip is just that.  Soldered with the legs on top of the board.  The other type of chip have legs that go through the board and are soldered under the board.

[otguy87]

A surface mounted chip is just that.  Soldered with the legs on top of the board.  The other type of chip have legs that go through the board and are soldered under the board.

Oh, they're soldered? Isn't this where the Flash Chip Key 40 thing goes though?
https://i.imgur.com/d5x9t5I.jpg
Since nothing has worked so far that I could do on my own (checking for bent pins, reseating the MPU), I am trying a Key 40 once it comes in the mail. Then if that doesn't work, try replacing the IO boards as someone else suggested.

[rickhunter]

That chip is on a socket, thus removable.  The socket is soldered to the board, and then the chip goes in the socket.  It is also no a flash chip, it is an eprom.

[otguy87]

That chip is on a socket, thus removable.  The socket is soldered to the board, and then the chip goes in the socket.  It is also no a flash chip, it is an eprom.

So much to learn on these. Thanks for the info!
I am hoping it is nothing on the MPU though. That seems like more of a tough fix than simply using the Key 22/40 or replacing the IO boards

[Tilt]

My bet is that you blew U74 on the MPU board.  It's not unusual for it to go if you pull or plug in the MPU board without turning off the power first.  Normally you'll get Coin in Jam error along with the meters disconnected error that will not clear, but not always.  Sometimes you can see physical damage to the IC (discoloration or a bubble on the top of it), other times not.  If you want to look at it for damage you'll have to remove your sound card that sits on top of the MPU board.

A bad I/O card can cause the same error messages, but you didn't remove them with the power on so it's not likely.   You needed a key for your machine anyhow, so it's not a waste of money getting one, but don't be surprised when it doesn't fix your problem.  I/O cards are pretty rugged, but can fail.  I'd buy a new MPU board before buying I/O cards though. 

Good luck!

[otguy87]

My bet is that you blew U74 on the MPU board.  It's not unusual for it to go if you pull or plug in the MPU board without turning off the power first.  Normally you'll get Coin in Jam error along with the meters disconnected error that will not clear, but not always.  Sometimes you can see physical damage to the IC (discoloration or a bubble on the top of it), other times not.  If you want to look at it for damage you'll have to remove your sound card that sits on top of the MPU board.

A bad I/O card can cause the same error messages, but you didn't remove them with the power on so it's not likely.   You needed a key for your machine anyhow, so it's not a waste of money getting one, but don't be surprised when it doesn't fix you problem.  I/O cards are pretty rugged, but can fail.  I'd buy a new MPU board before buying I/O cards though. 

Good luck!

Oh dang, well, I guess I will find out eventually.

But I am enjoying that I am learning so much on these machines through you guys, so again, thanks a lot for the input.

So what is the U74? I don't see it:
https://i.imgur.com/MTEq8cT.jpg
So, just to clarify, this entire board is the MPU? And the small top part I took off is the sound card?
And I can just buy any MPU as long as it is the same part number 75703902 REV A?
Sorry for 50 Qs. Trying to learn as much as possible.

[Tilt]

I circled U74 in red on the MPU board, and then made another circle inside it where it looks like it may be damaged?  Can't tell for sure in the photo.

Yes, the entire board is known as the MPU board and the daughter board that plugged on to it is the MML2 (Multimedia Lite 2) board (AKA Sound card). 

No problem, ask away, that's how ya learn.

[otguy87]

I circled U74 in red on the MPU board, and then made another circle inside it where it looks like it may be damaged?  Can't tell for sure in the photo.

Yes, the entire board is known as the MPU board and the daughter board that plugged on to it is the MML2 (Multimedia Lite 2) board (AKA Sound card). 

No problem, ask away, that's how ya learn.

Well son of a gun, I think you are right. It does have a raised bump to it, and what looks like possible burnt marks near the bump. It is hard to get a really good picture of it, but since it does have a bump and nothing else does, I assume it did "blow up".

https://i.imgur.com/tS1azw4.jpg

I even had my girlfriend look for U74 because I couldn't find it. Either could she lol.

But dang, I was hoping it would be an easy fix.  I don't mind having backups so I am not mad I purchased the IO boards plus the Key 40.

However, I cannot seem to find this board anywhere to buy! It seems like they are all Revision Bs, and I need to stick with Revision A, correct?

Actually, the only boards I can find are these:

https://www.ebay.com/itm/L-K-Slot-Machine-IGT-Game-King-Video-Controller-MPU-Board-75703902-L-K/284007460967?hash=item422029f067:g:imUAAOSwz2pfWoLh

Which is REV B, and this, which doesn't even state which REV it is:

https://get-t.net/product/igt-gameking-cpu-board-igt-part-75703902-gett-part-cpu135/

Ugh

[otguy87]

No problem, ask away, that's how ya learn.

And not to get too off topic, but where is the game stored? Is it the chips that have the red stickers on my MPU?

[Tilt]

Spare parts are always a good thing with these machines.  Makes it easier to troubleshoot future problems. 

Yep, it's toast.  If you have the skills/equipment to remove and replace surface mount components that would be the cheapest way to fix it.  Most people don't, so it's easier and cheaper just to replace the MPU. Rev A/B doesn't matter, any 3902 board will work (that number is derived from the last 4 digits of the MPU part number).

G2Gliquidators is a member here, but they're liquidating parts from casinos and I'm sure it is all "as is" not tested.  You could check with him to be sure.  I think it would be a roll of the dice.  Might get it cheap, but it might not work.  You'd be better off getting one from a vendor here, they'll take care of you if you have any problems.

Yes, you'll have to remove your base chip, GME chips (all eproms) and then SIMM cards from the old board to the new one.  The horizontal one under the MML2 board is the CGF simm, it has to go in the same place on the new board.  The vertical SIMMs are PXL cards and can go in any of the three slots.  Best to keep them in order if you have multiple ones, just for organization sakes.

[otguy87]

Spare parts are always a good thing with these machines.  Makes it easier to troubleshoot future problems. 

Yep, it's toast.  If you have the skills/equipment to remove and replace surface mount components that would be the cheapest way to fix it.  Most people don't, so it's easier and cheaper just to replace the MPU. Rev A/B doesn't matter, any 3902 board will work (that number is derived from the last 4 digits of the MPU part number).

G2Gliquidators is a member here, but they're liquidating parts from casinos and I'm sure it is all "as is" not tested.  You could check with him to be sure.  I think it would be a roll of the dice.  Might get it cheap, but it might not work.  You'd be better off getting one from a vendor here, they'll take care of you if you have any problems.

Yes, you'll have to remove your base chip, GME chips (all eproms) and then SIMM cards from the old board to the new one.  The horizontal one under the MML2 board is the CGF simm, it has to go in the same place on the new board.  The vertical SIMMs are PXL cards and can go in any of the three slots.  Best to keep them in order if you have multiple ones, just for organization sakes.

I agree. I like the insurance of having spare parts in case anything goes wrong one day. Plus, this is now probably my new expensive hobby. I just want to buy more older machines.

I actually had a vendor PM me so I have one coming Also PMd another vendor for purchasing a backup or two, because I do plan to get more of these old IGT machines.

You have been really helpful in teaching about these things, so I appreciate it.

It's late and man, those abbreviations for the chips hurt my brain. I will look at them all tomorrow lol.
Do I need special tools to remove any of these? Or will just a small plastic flat head tool to pop them out work?

[Tilt]

A small screwdriver will work to remove the ICs from the socket, but it's not the right tool to use with any frequency.  Be careful because what usually happens is you'll pry up one end of the IC and bend the legs on the other end.  That's OK, until you go to straighten out the legs to re-install it on the new board and they break off because you weren't the first one to bend them one direction (weakening them) and then the other and they break off.   It shouldn't happen if you're careful removing it equally one each end, which isn't easy with the MPU board mounted in the tray.  Just take it slow and be careful removing them and you shouldn't have any problems.

Be just as careful re-installing them into the new board that you don't bend any pins over.