(Topic ID: 231618)

Replacement Capacitors for 6803 MPU/SDB

By jlbintn

4 years ago

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  • 62 posts
  • 6 Pinsiders participating
  • Latest reply 3 years ago by jlbintn
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#1 4 years ago

any sources for the following that anybody could point me too?

160uf 350v
470uf 35v
470uf 25v
11000uf 20v
2uf 25v
.1uf 25v
.01uf 500v

Not even sure I need to replace all of them, but trying to be thorough.

This is for a Dungeons & Dragons machine, which plays fine but recently has taken to strobing on the score displays. I have a set of Xpin's that will just not work, and I'm not sure the issue is with the Xpin displays. So, I want to start with the capacitors.

I put some LED's on the four bumpers. Just wanted to jazz it up a bit, but not go overboard. It looked good, especially since three of the bumpers on this game are covered by plastic artwork.

Worked fine for almost two weeks, then the strobing began. Took the LED's out, and the problem did not go away. Disconnected and re-connected all harness plugs from the MPU board, and now one of the original plasma displays not only strobes, but it displays gibberish.

The XPin's just don't display much of anything, except lines that are a part of the digit that should be displayed.

Anyway, any info or tips would be appreciated.


#3 4 years ago

What type of capacitor am I looking for?

I'm assuming Axial Filter Capacitors, for the big one, radial for the really big one.


btw, there are no tolerances - high or low - that I could substitute are there?

for instance 10000 uf 16v will not be acceptable for the 11000uf 20v cap? I am assuming this works both ways - high and low. Close is not good enough, yes?

#5 4 years ago

Ok, thanks a lot. That is quite helpful.

I measured voltages on the SDB and this is what I got

TP1 - +5vdc, read +5.16
TP2 - +190vdc, read 146vdc
TP3 - +230vdc, read 152vdc
TP4 - +43vdc, read +45vdc
TP5 - +14vdc, read +16.8vdc
TP6 - 11vac, read 10.6vac
TP7 - 11vac, read 11vac
TP8 - 6.3vac, read 6vac
TP9 - 6.3vac, read 6.1vac

I have no idea - at this moment - what the voltages for the MPU board should be. I've got a really crappy copy of the manual. Everything up til the schematics and board layouts are fine, but the schematics are terrible. I could find no voltage readings on that board so I didn't even measure them for the time being.

There is an adjustable pot on that SDB, I played around with it from high to low but saw no variance in the readings I got on the high voltage tests so idk....

I was fortunate to find an original owner's manual for my Fireball II game, but D&D seems to be scraping the barrel. I have yet to find a good copy. Reading schematics that are broken into single one-sided pages, and crappy copies at that, is not conducive to a good mood


I have not re-pinned any connectors on this game. Examination shows every connector in the backbox, save one, to be in pretty remarkable shape for a game that is over 30 years old.

The main power connector has some burnt plastic around one pin, and that was as a result of a solder connection that I discovered over the summer, that had deterioriated. That's the best way I can describe what I found while I was tracking a board lamp that I could not get to work. I cleaned as best i could the back of the board, re-soldered it and plugged the connector in, replaced two transistors and all lamps were then functional.

I will have to rework that connection, but for the time being the pins look fine (not burnt) so I think I can live with it for a bit longer. I have been very fortunate with the two Bally games I bought as is, when it pertains to connectors. I ended up replacing all of the backbox connectors in my Fireball II game, during the play-field swap, but I really don't think I needed to do that.

Peace of mind I reckon.

Is there anything else in that backbox that I might want to investigate, as it pertains to power supply? Also, I did not measure for AC ripple. Will do that tomorrow, but I found the caps and ordered them. I've got a Donkey Kong CRT cap kit that needs to be jobbed soon, so I figured I might as well do both at the same time.

#7 4 years ago

Yeah, you confirmed what I was beginning to suspect after I took those readings.

Thank you.

#9 4 years ago

Went digging into some e-mails between myself and Brett at XPIN, from October. These were the voltages from that SDB on October 26th of this year

TP1 +5vdc, reads 5.2vdc
TP2 +190vdc, reads 174.4vdc
TP3 +230vdc, reads 234vdc
TP4 +43vdc, reads 45.5vdc
TP5 +14vdc, reads 16.9vdc
TP6 11vac, reads 10.4 vac
TP7 11vac, reads 10.4 vac
TP8 6.3vac, reads 6.2vac
TP9 6.3 vac, reads 6.3.vac

I still had the issue with the XPIN displays, so whatever occurred with that SDB between then and now, I think I have another issue 'hiding in the shadows'...

or maybe not.

I hate the weird ones, but when they're discovered they're not so weird. Chasing ghosts LOL

#11 4 years ago

Any suggestions on what it "may" be? I know that's a loaded question, but eventually I'm going to have to get there, after I resolve this issue.

Anyway, metered D5-D8 with power off and unplugged. They metered within specs - .5 on all - and null with leads reversed.

Could I use 4007's instead of 4004's, if I ever have to replace them?

#13 4 years ago

ok, thought so

I've got a lot of 4007's, as that's what I used to replace switch diodes when I did the play-field swap on my Fireball II. Got a few left

#16 4 years ago

The XPIN's never displayed properly, other than test mode. They displayed full digits, brightly and clearly. With the game idle, and in attract mode, they displayed very little at all, but there was, and still is, no strobing.

If it is the cable, shouldn't the issue be present regardless of what is connected to that harness, even taking into consideration the XPIN's do not use high voltage to do their job? Neither side of the scoring display performs correctly, with the XPIN's, although both test properly.

With the plasma's connected, it is only the right side scoring display, that displayed gibberish, but even that disappeared approximately 6-8 weeks ago. By right side I am referring to the scoring displays as you look at the back-glass from the player aspect of the game. Got that with both plasma's, irregardless of which display was connected to the right side harness.

Additionally, there is no ribbon cable, anywhere in this game. Is that just a generic reference? Or a reference to the connector type? Trying to get the jargon squared away here so I don't post something that I'll later re-read and feel stupid for not posting correctly

Anyway, the game is on right now. I leave my games on, and in attract mode, probably 60-70% of the time. They light the rooms up nicely, and I have found that the games seem to "like" being on over time. Same same with my arcade games. That may just be me, but I put it out there in the way of an fyi

So to sum it up, the plasma's display properly - now - but there is this new problem of strobing. It looks like we have identified the source for that. The XPIN's, there is no strobing, but improper display, other than in test mode. So that is where I am at.

I have not re-pinned any connectors in this game. I have replaced several transistors on the MPU board, to resolve play-field lamps that were not functioning. Outside of that, and the connector pin on the SDB I referenced earlier, there has been no work on this game afaik. The boards in the back, look to be in remarkable shape and I am guessing that they have never been out for service. I do believe these boards may be as they shipped from the factory when this game was new. The original battery is still on the MPU board and is in remarkable shape, with absolutely no corrosion whatsoever.

I plan to replace it with a battery pack as soon as I get the parts I need, as I have seen what a battery can do to an MPU board. But that battery being in there, suggests to me that no work whatsoever had ever been done on any board in the back-box of this game, prior to what I did this past summer. I have pulled the SDB and the MPU boards from the backbox, and they look stock. That there are now issues, may be due to the fact that the game is getting normal use that it may never have had in the past. I don't know it's history, other than since early 2007, when I purchased it. But it is a 32 year old game.

#18 4 years ago


Got the high voltage section repaired, strobing is gone. I did not get terminal studs with this capacitor. It's the big one at C1, and is much bigger than the original, although I can make it work. The supplier told me that those threads are 10/32's, so I should be able to find something in the shed, but the strobing is gone with the old one still in place, and all readings are within spec.

Four LED's in those bumper coils should not be stressful, should it? I haven't put them back in, and may not. The replacement cap at C2 is much bigger than the original, as well. I had to wrap the negative lead under the bottom of the board and solder it from behind. Got it insulated with electrical tape underneath the lead between the lead and the board and over the top of the lead, just to be safe.

Anyway, now on to the XPIN's which I believe is going to be a more involved and tedious problem.

I will keep this thread updated, and feel free (please) to throw in any thoughts any of you may have.

Thanks a lot for all of the help to this point.

003 (resized).JPG
#20 4 years ago

According to the +5 volt section in the link provided earlier in this thread

+5 Volts Problems and Fixes.
The first thing that should be replaced in the +5 volt section is the big capacitor C1 (11,000 mfd 20 volts). This is the main filter cap that smooths the input AC volts. This filter cap has an effective life span of about ten years. That means that *every* 6803 game should have this capacitor replaced! Symptoms of a bad +5 volt filter capacitor are random game resets and lock ups.

Cap C1 can also be tested with a DMM set to low AC volts. Put the leads of the DMM on each lug of cap C1 with the game powered on. After a moment, the meter reading should stablize and show no more than .25 volts AC. If there is any more than 1/4 volt AC, capacitor C1 is definately bad.

>>>> Tested this, reads a constant .21 - .22 range <<<<

Other than the filter cap, diodes D1,D2,D3,D4 (MR751, 100 volt 6 amp) also handle the initial conversion from input AC volts to DC volts. Check diodes D1-D4 with a DMM set to the diode function (.4 to .6 volts in one direction, null reading in the other). If any of these four diodes goes open (null reading in both directions), the +5 volts won't work at all. If any of these four diodes shorts (less than .4 volts), this will blow fuse FU3 (6 amp slow-blow). Diodes D1-D4 can be replaced with any 6A1 style diodes.

>>>> Either I'm going blind, or there are no D1-D4 diodes on this board. So, what am I missing? My 5 volt section is working based on previous posts and replies, but where are these diodes? <<<<

#22 4 years ago

yep, I recognize them. Looked right at them and cannot see the D1-D4 even after knowing they're there.

Thanks. I need a good schematic.

#23 4 years ago

measured them and they're reading 0.4, with the leads reversed all are reading between 0.8 and 0.9

that is with the game off and unplugged.

#26 4 years ago

the first link is about like my actual manual, the second, specifically the schematic section will be very helpful.

Thank you very much

#27 4 years ago
Quoted from wayout440:

No problem there. Your meter measurements are indicating the forward voltage drop of 0.4 and a reverse bias near the meter supply voltage for each diode.
Anyway the point is moot, you already know the +5VDC voltage is fine. The game wouldn't run without it, If you are still trying to work on the XPIN displays, do any segments light up? if so it is getting 5VDC.

Therefore, since you said you had full bright digits here with the display test. That also proves no problem with the +5VDC,

I was just being thorough and I looked right at those things but it was the angle (from the right) and I couldn't see the silk screen labels for those four diodes. I feel kind of silly for not catching them from the other side, but most of the time I have worked on this game it is from the right side.

Anyway, I am moving forward with the assumption that something on the MPU is most likely the issue. And see what happens from there. I have spare board parts, leftover from Fireball so the money is already spent. I'm going to try to track it down myself, before sending it out for repair.

And as you stated, the XPIN's are fine, just not displaying full, hardly any, digits. Other than in test mode.

1 month later
#28 4 years ago

Finally got to the connectors today. What a PITA, especially on the left display as the original connector was a .100 IDC style connector plug, not a terminated .100 molex. On .100 connectors that is brutal, because I had to double up each wire to the new connector. The loops (there were three) really sucked

Worked well, but I probably should get some spare IDC .100 connector plugs. I don't want to do it this way again

Still no joy with the Xpin's, status quo is still the status quo. So on to whatever is next.

#29 4 years ago

D&D (resized).jpg

#30 4 years ago
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5 months later
#31 3 years ago

Still working on a resolution for the failure of my XPIN's to not display properly. What is the proper way to meter an IC, in this case the 6821 at U7? I should be able to meter voltage at each pin with the game on, yes?

Going by the information at pinrepair - using a test setup - am I wrong to assume I can meter the boards in game in the same manner as I would if I had a similar test setup as that used in that link?

3 weeks later
#33 3 years ago

Just in the way of an update:

Replaced U13, new chip and added a socket in that slot. Replaced the 6821's at U7 and U8. Burned two new CPU roms for U2 and U3. Still no luck getting the XPIN's to work. The SDB has been, for the most part, completely rebuilt. I replaced all of the board side connectors and the high voltage section, as already stated was completely rebuilt and is functioning fine. The game plays well, with no quirky behavior at all.

I live in southeast Tennessee, in the Cleveland area. Is there anybody here that lives within a reasonable distance that has a working Dungeons & Dragons pinball machine? I would really like to try these things in another known working machine, if one is willing to help.

This is getting frustrating. I know those plasma's are not going to last forever.

#34 3 years ago

got a logic probe, still figuring out how to use it so please bear with me. Set to TTL and Pulse I took the following readings off of the 6821 at U7 on the 6803 Control board. The second figure represents what I metered with the DMM. All voltages are DC. I am assuming that when both high and low are on, that is pulsing. The sound was different as well

1 - Low (.03 - .05)
2 - Pulse (.55 - .58)
3 - Pulse (.12 - .14)
4 - Pulse (.11 - .14)
5 - Pulse (.07 - .17)
6 - Pulse (.08 - 4.36) This one was odd, not sure if I didn't short it to another pin. I took the reading a couple of times, though.
7 - Pulse (.05 - .17)
8 - Pulse (.05 - .16)
9 - Pulse (.06 - .12)
10 High ( 5.10)
11 High (5.10)
12 High (5.10)
13 High (5.10)
14 Pulse (.20 - .24)
15 Nothing (1.88 - 1.91)
16 Nothing (1.89 - 1.91)
17 Nothing (1.89 - 1.91)
18 Nothing (.01 - .02)

based on what I read at pinrepair, Pin 1 should read 5 volts, 2-18 should read between 1 and 2 volts. So, that's where I am at right now.

#36 3 years ago

With J1 disconnected on the Control board, all DC voltages read pretty much the same. 5vdc was 5.2 disconnected, 5.16 connected. +14 vdc read 17 disconnected, 16 connected.

Those were the only variations I noticed.

The hunt continues

thanks for the reply.

#37 3 years ago

Measuring U1 - 21-40 as per pinrepair Address and Data lines

21 - 5.12
22 - 4.05
23 - 3.73
24 - 0.82
25 - 2.46
26 - 2.77
27 - 2.60
28 - 2.08
29 - 2.35
30 - 2.39
31 - 2.42
32 - 2.55
33 - 2.60
34 - 2.43
35 - 2.72
36 - 3.00
37 - 2.04
38 - 3.83
39 - 1.02
40 - 2.48

24 isn't missing, but it is low. 21 is a bit high at 5 volts. With the exception of pin 39, all of those pins should read between 2 and 4 volts. So, the processor may be the culprit.


Readings taken with the game in attract mode, ready to play. I have no test setup at this time. Pin 3 clock signal is measuring 1.02 volts.

#39 3 years ago

U7 Pin 1 0.02 - 0.05
U8 Pin 1 0.02 - 0.05

at the lowest DC setting on the meter, the reading cycles between those values on both PIA's.

#41 3 years ago
Quoted from wayout440:

That's no good. That game will not work. Check 5VDC at TP1 (this is right after where it comes in the board on pins 10,11, and 12) Do you have it at pin 1 on U2 and U3 (the PROMS)

TP1 is good at 5.17vdc. TP3 reads 15.9vdc. Both PROM pin 1's read 5.15vdc.

The game plays just fine, too. Scoring works, settings menu's all work. Flippers work, all tests on all lights are working. All coils firing, etc. My grand-kids just got done playing a couple of games.

Only thing I can't get to work are the XPin's. <shrugs>

oh btw, I'm just venting now: I so want to burn Section 2 of the manual I have. Totally useless, and working a problem like this, makes it even more frustrating

#44 3 years ago

Unfortunately, it wasn't a measuring error on my part. On two DMM's, I'm getting the same thing.

Now, I am assuming that the data sheet I looked up for the 6821 is correct, and Pin 1 is at the top left.

The HV's are working fine. One of them is showing signs of age - brightness in a couple of digits is weak at times. I swapped it from the left to the right and the problem is consistent, so I am relegating that to old age. The old HV's in my Fireball II were doing the same thing, but they worked. Newer displays fixed the problem right up

#45 3 years ago
Quoted from wayout440:

If the scoring displays work and the game plays fine, then there's no need for all the troubleshooting of the control board. The problem can only be something off the board, most likely a problem with the XPin.
Defective Xpin display
Firmware problem Xpin
Cabling problem (again, least likely if the original HV displays work properly)

Just running off at the keyboard right now....

yeah the game is playing fine. My wife could not stand this game (the magic-saves drove her nuts), she was use to old school pins, and initially, this game was kind of relegated to red-headed step-child status because I got it at the same time I bought her Lord of the Rings

But she's started taking a shine to it, as have our two grand-children. With the flipper rebuilds, the game got faster. Not dramatically, but you can feel it (her words) and see it during play.

It's a damn cool game. The sound system sucks, reminds me of old school LP's, 33 or 45 but especially 78's

#46 3 years ago

What does SW1 do on this board? Is it for testing only? If I press it, should it cycle through the boot process, as the board does during initial power-up?

I press it and it does nothing. No flashing LED, nothing. The LED flashes nine times during initial power-up.

#48 3 years ago

That was my suspicion as well.

Adding that to the list of things to get.

#49 3 years ago

Took SW1 off. Based on a fairly decent schematic of that MPU for a Special Force game, Pin 1 on U7 and U8 is not the physical pin configuration as the data sheet shows. It is actually at the bottom left instead of the top left and that pin reads a consistent 5vdc. Same with U8. So, it was a metering error on my part. And, that is a relief actually.

Those schematics for Special Force aren't the best, I had to blow them up to 390% but pretty sure I read it correctly. That would make sense as well, based on readings I've metered, and posted already. From D5, through SW1, U7, U8 all the way through U17, that trace reads consistently with the voltage I posted for what I thought was Pin 1, e.g., .03 - .05

So, that is just an FYI and that is where I am at.

3 weeks later
#50 3 years ago

Replaced SW1. Still does nothing when pressing it. Not sure if it's supposed to do anything, but the same switch on the sound card does generate a test sound.

Just reaching at solutions now, but does anybody know of an aftermarket connector kit for the 6803 display boards? The connectors are fine, but at this point with the XPIN's I'm getting "desperate".

One of my display cards is giving me indicators that it may be getting tired. I'm not sure if they are worth repairing, and even if I choose that route, I don't know the extent to which it would correct some of the fading I'm seeing during certain attract mode segments. I had one out over the weekend, and it's not going to be a ten minute job. The plasma glass stickies feel like they're doing their job very well, even after all of these years of service

#52 3 years ago

Thank you very much for sticking with this. I can not express how much I appreciate that. This issue is driving me crazy.

Not just SW1, but you know the rest of that story.

As an aside, and somewhat unrelated, I have an occasional issue with my Fireball II not wanting to boot up on first attempt. A quick toggle of the ON/OFF switch always brings it up the second time.

That's a known issue, but it's not a priority at the moment. First things first

#53 3 years ago

Ok, have to ask, pardon me if it seems a stupid question, but what does direct to ground mean? I used a DMM with the leads on Pin 4 and TP2, but it did not simulate the reset. Continuity is good, also read +5vdc at pin 4.

I also purchased a second 6803 about a month ago, so I had two to work with. No difference with either installed on the MPU. Also, an NVRAM would not have any effect here, would it?

I can't see why it would.

edit to add

Is there anybody around here that works on 6803's? I want to continue on my own, but I may be nearing it's above my pay grade territory.

#55 3 years ago

Ok thanks, that is what I suspected, but I wanted to make sure before proceeding, for the very reason you provided.

#56 3 years ago

I've called this one. Sent the 6803 MPU to Eldorado Games. That SW1 issue needs to be diagnosed on a scope. I've been at this for almost a year, and I have reached the end of my ability for the time being.

One last question for this topic for now.

On the power supply board, the 230 in sometimes reads as high as 244vdc. It's unregulated, so that shouldn't be an issue, correct?

#59 3 years ago

All other voltages are good. I did not think that it was an issue. I've got the displays turned down to 170vdc. I am very interested in what a full diagnostic on that board turns up.

And Brtlkat, yes my strobing is gone. Fixed that last year with new caps, and a rebuild of the high voltage section of the power board

2 months later
#61 3 years ago


Sent my 6803 MPU board to Eldorado Games. Talked to John yesterday, and was told that there is nothing wrong with the board. He also told me that SW1 on that board doesn't do anything. The board checked out good on the test bench, so it appears that my XPin displays just do not work with this particular version of the 6803 MPU.

So now, I'm "stuck" trying to find some newer displays that this MPU will be able to talk to. He said something about different versions of the 6803, so if that's true - and atm I have no reason to disbelieve that after my 14 month trek with this game and those newer displays, I'm hoping that there are some versions out there like Pinscore or Pinball Solutions that may resolve the issue. I've looked for replacement high voltage 14 digit displays, but those seem to almost as rare as a dinosaur.

I wonder if there is a way to get them to work. I wonder if anybody would even be willing to put the effort forth.

Any opinions? Any suggestions? Does anybody have a D&D pin that is using XPin's? If so, what Revision of the displays are they? I have a pair of Revision A's.

1 week later
#62 3 years ago

Update and a shout out for Brett at XPin. For the better part of the last 15 months, we tried to work out the issue with these displays, to no avail. I highly recommend XPin for display needs, as Brett is a good guy and stands by his word and his product. He went the extra mile for, and with me, to attempt to resolve this issue.

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