This surely doesn't seem to be my week at all...

After blowing the optos on my TZ mini playfield by putting the molex connectors together incorrectly (duh!), now I'm having a problem with my Stern Monopoly.

I've owned this pin for 14 years; it has all of the original boards in it. I've never really had much of a problem with it. The last time I played it was three days ago, and everything was fine. Today I power it up, and some of the GI lights flicker a bit, the message board freezes, and the DMD shows nothing. Needless to say, it won't boot up.

I checked the power board and discovered that the 8A fuse at F22 had blown, and the 18V indicator was dim. I replaced the fuse and that one blew too. I removed all of the other fuses and checked each one, and they were OK.

So somehow something is going on with the 18V. Anyone have any ideas about this? I'm very much the novice when it comes to this, so anything that anyone can suggest would certainly be appreciated.

Thanks in advance!

Hey LTG-Thanks for the advice. I'll check that out tomorrow.

OK so I pulled my board today, and I found that BRDG20 comes off of F22. I looked up how to test a bridge rectifier (having never done this before!), and set about testing, with my DMM, every bridge on the board, so as to have some kind of base reference. While most of the legs measured anywhere from 520-570, one of the legs on BRDG20 measured 495. Would this be enough of a difference to make this a bad one? I was under the impression that if it was bad, the number should be waaaayyyy up, like 1600 or something).

Again, this is all very new to me, and I thank you for your patience. Should I just go ahead and replace it?

OK sounds good. I'll order some replacements (along with 8a MDL fuses, as I blew my last one!), and get to work.

Once again, thanks for taking the time to help; I really appreciate it!

Well, I received my parts and set about replacing. I put in a KBPC3504 bridge (apparently, this is a replacement for DB3501), put in a fresh 8A fuse, turned on the power, and the same thing happened! Lights flicker for a second or two, then nothing. The fuse blew out again after a few seconds of stress. So I'm guessing something else is at fault here. Should I have also replaced the two capacitors (each is 15000uF at 25v), or is something else going on here?

As a side thought, I'm wondering if it would be OK to take the "defective" board and put it in another pin that I have (South Park) and see how it performs. Perhaps this way I would be able to determine if the problem is "on board" or "off board". Is this OK to try?

OK here's an update...

I took the board out of Monopoly and put it into South Park; it works perfectly. So, I guess I can rule out the board as the issue.

At this point, I'm rather reluctant to put the SP board into Monopoly; I really do not wish to risk damage to the working board, plus I don't see any real benefit to doing so at this point, as I don't think I would gain anything of value from that move.

So, something off the board would seem to be in play here. Possibly transformer? (although the only line affected is the 18v on the board; all other LEDs show as OK).

Ah, actually, I did. I replaced a piece of plexiglass that I put on the side ramp to prevent the ball from flying off. I suppose something might have been disturbed when I did this, although it did play OK for a bit after I did that initial work. Anything is possible, I guess.

After your suggestion, Maniac, I went to the manual to see exactly what is coming off of that 18v. It leads to connector J13, which is for the "controlled lamps", along with a single blue wire at position 10 that goes up to the Display Power Supply board, which in turn then goes down to the DMD. I put the power board back into the game and reconnected everything except for the J13 connector. I turned on the power and all was well. I then turned it off, connected J13, but this time disconnected the blue wire up to the Display Power Supply. I powered it up, and once again the playfield lamps started flashing quickly like before, so I turned it off immediately before the fuse blew.

So, as you have suggested, I am guessing that there is indeed a short somewhere on the lamp matrix, so I'll need to check that out. There's 80 lamps on the matrix, so I guess I'd better get started!

Let me say at this time that I greatly appreciate all of the help and suggestions that are coming in about this. One of the things I truly like about Pinside is how everyone is willing to help those in need. Thanks so much!

Man, this thing is beating me up but good...

I spent a good part of yesterday checking things out; I have yet to find any sort of short in the lamp matrix. I was looking for any kind of exposed wires that might be touching metal. I inspected as many of the bulbs that I could get to. So far, no success.

Here's something I did notice, though. I turned the power on in short bursts (so as not to blow the fuse) to see which lamps lit and which didn't, so that perhaps I could get an idea of maybe where the short might be occurring. When I turned the power on, the lamps that did light were overly bright, seeming to indicate heightened voltage. What I also noticed was that the lamps in the last two complete rows of the matrix (#65-#80) did not light. Perhaps this is where I need to turn my attention to?

Also, as an aside, I also found this lying in the bottom of my cabinet:

20180731_100849 (resized).jpg

This looks vaguely familiar; a contact of some kind? I'm wondering if perhaps a portion of this broke off and is touching something that it shouldn't be?

I'm keeping at it; hopefully I can find something today.

OK, so here's another update...

I spent the last three days going over just about every lamp on the matrix, removing each bulb and testing each diode, jiggling wires and looking for anything that might be out of place (frayed and/or cut wires touching metal, etc.). Nothing.

After another check this morning and running out of ideas, I decided to swap out the CPU/Sound board this time, and try it in my South Park, as I figured I had nothing to lose by trying at this point. Interestingly enough, when I turned the power on, SP started to behave in a similar manner as to what was happening on Monopoly; lights flashing on and off, no DMD display, but this time with a relay clicking. This behavior I remember from many years ago when I had a problem with the original SP board, which I eventually needed to send off to get repaired.

So now I set out to put the SP CPU/Sound board into Monopoly and low and behold, I worked perfectly!

At least now I know I have a problem with the CPU/Sound board. What I did notice in the faulty board is that the indicator LED marked L200 is dim. I'm assuming this has something to do with the DMD? I'll need to consult my manual and start investigating.

If anyone has any further info that they would like to share, please feel free to do so.

Update:

So I took out the CPU/Sound board once again and began to go over it, checking all of the socketed chips and so forth, when I discovered this:

Monopoly CPU-Sound board (resized).jpg

Interesting that I had never noticed this before. I hadn't even thought about it, really, as I put in a NVRAM almost a year ago.

Looking at the image, one can see some possible corrosion on the right solder points of D200 and D201, inside the yellow circle. Also, obvious corrosion coming from the battery holder to the outside ground line, as shown inside the red oval. At the lower end of the red oval, it just touches the trace that leads to the top right pin of the NVRAM socket.

Once again, being still rather new to this, could this possibly be the source of my woes? I figure that at least while the board is out, I'm going to remove the battery holder from the board. I also saw on Pinwiki in the section about Whitestar an example of a board in similar, but a bit worse, state that had the traces sanded, treated with 50/50 vinegar and water, and then tinned with solder.

Any thoughts?

Thanks for the tips...

Clear nail polish, eh? Who would have thought? I actually do have some in my instrument repair kit (musical instrument, that is. Clear nail polish is great for putting on tiny screws to stop them from backing out, particularly on clarinets.). I also heard that an epoxy like JBWeld could be put over the traces to protect them.

I'm not all that certain, either, that this is actually the cause of my problems; I'm about 50/50. Researching on Pinwiki, the symptoms that are being displayed are consistent with battery damage, although I'm not certain that the corrosion damage is sufficient enough in this case to be causing it. At any rate, no harm will be done by taking off the battery holder and doing the repairs. I'm waiting on replacement 1N5817 diodes, two of which sit under the holder, that are going to be delivered tomorrow (Thanks, Amazon!). After that, we'll see.

BTW, you did notice that I have Pinitech NVRAMS on this, yes?

Again, thanks for your advice. I greatly appreciate it.

Yes, I did swap out the EPROMs. I put Monopoly on the SP CPU board, put the board in Monopoly, and all is well, so that rules out the EPROM.

I didn't try swapping the NVRAM, though, as I really don't suspect that is the issue. I'm going to try that and see, just to be sure.

UPDATE: Well, I just swapped the NVRAM; it's OK.

I cleaned up the corrosion on the board this evening, so it's all ready to go when I get the diodes tomorrow. Hopefully, I'll have a happy ending.

Definitely going to check out the chip burner; then when I have some scratch I'll make a purchase.

Again, thanks for the advice.

Well, I just completed the repairs to Monopoly's CPU/Sound board. I put it in, fired it up....and it's still doing the same thing.

I kinda figured that it was going to be a 50/50 shot at best anyways; at least I repaired the battery corrosion to my board.

I guess the answer lies elsewhere; I'm going to keep diggin'...

Here's are a couple of pics after I cleaned up the corroded area; I don't know if these are sufficient, however:

CPU #3 (resized).jpg
20180805_203446 (resized).jpg

I can take a fuller picture tomorrow.

Here are some other photos of the board, which I took just now:

CPU #1 (resized).jpg
CPU #2 (resized).jpg
CPU #3 (resized).jpg
CPU #4 (resized).jpg
CPU #5 (resized).jpg

From what I can see, things look pretty clean, although I am a novice at this and perhaps I'm missing something still.

THANK YOU!! Again, this is the first time I've ever attempted something like this, so to receive some positive feedback really helps. Also, nice to know that perhaps I didn't wreck anything further.

Yep, I did indeed swap that out; it works fine on the other CPU.

Agreed; that's why I didn't think much of it.

Thanks for looking, though. The more eyes, the better I think.

Update...

Well, I think I have taken this as far as my limited knowledge and abilities can handle. I have decided to send my board out for repair, to the very capable hands of Chris Hibler, who agreed to take it on. I have no doubt that he will be able to find out what's going on.

I'll report back when I know anything further. Thanks to all who offered guidance and suggestions up to this point; I really do appreciate it!

Update...

Well, after about a month, I am now happy to report that Monopoly, as well as the owner, is once again happy. I received my board back from Chris today, popped it back into my machine, and all is well once again.

Chris did GREAT work on my board! He kept me apprised of what was going on, and he even sent a video to me of my board attached to his Whitestar rig, working in all its glory, after it was repaired.

It appears that the initial idea of alkaline damage was correct, although it needed to be taken further. There was indeed damage under the RAM socket just below what I had already repaired, as others had indicated it might. I'm glad he did it, though, as I'm not at all sure of how to even begin with removing a socket from a board.

Here's a pic of the repair (without the NVRAM installed):

20180913_154829 (resized).jpg

So, all's well that ends well. Now I can finally remove this sign from Monopoly:

20180913_154902 (resized).jpg

Once again, thanks to all who helped me with this!