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The switched lamps on a 6803 game driving me nuts.

Game On

Game On

Banned
Joined
Mar 10, 2020
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127
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Cheltenham
I am attempting to repair a Bally Special Force Game.. Everything boots OK and you can start a game. However there are 6 switched lamps that are driving me nuts. I will explain....
When the game is switched on and before the MPU boots there are 6 controlled lamps that are on. Once the boot sequence has finished these 6 go off and the game is in attract mode and lamps are flashing all over the place but for the 6 that were on at the beginning. Sometimes they flicker and even come on and act normal it is almost as if I have a loose connection. Bearing in mind this is not a lamp matrix but a "Bi-Phase" system. Each lamp has a dedicated SCR that controls 2 lamps The attract mode will be working perfectly but is you turn off the game and turn it back on, the fault come back . I am 100% certain it is not the MPU as I have changed it for a known good CPU board and the fault is exactly the same so it must either be the wiring or Power Supply I have checked both and the system used 20volts AC with a centre tap that produces 10volts AC on 2 different phases. This is what I have done

I have changed the MPU board with no change I have run a new earth to all the offending lamps with no change I have run new cables from the MPU for the switched signal with no change I have put new Header pins in THE CPU and also re-pinned the connectors with new pins and housing, I cannot understand why the lamps flicker as if it is a loose connection. All I can think of is a shorted diode somewhere, but why would they flicker? Do SCR's go intermittent? But as s I have said it is not the CPU and the PSU is delivering the volts needed
Any advice would be much appreciated
 
Having identified the 6 specific named feature lamps on the schematics (pg 2-18) is there any commonality of components on the lamp driver board?
 
astyy said:
Having identified the 6 specific named feature lamps on the schematics (pg 2-18) is there any commonality of components on the lamp driver board?
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Hi. The way the 6803 game works is that the driver SCR light 2 lamps one on the positive clyle and one on the negtive. I initially though it could be the SCR but bearing in mind I have changed the MPU board for a known good one proves the MPU and its components to be good. I also meant to add that if you go into lamp test, all lamp flash normally but when testing individual ones the lamps in question stay dark I have phsically run wires from the power board and MPU to the lamps in question and still no joy. Then all of a sudden it would start working normally. Logic says it must be the either the Wiring , MPU or power board. I know 100% that the power board is producing 20volts AC with a centre tap The MP has been changed and new wiring. As far as I can see the only thing left are the diodes across the lamps in question I have never had such an awkward fault before?
 
Pudsey pinball said:
Check solder joints on boards 6803 well known for bad solder and crap connectors and pins.
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I have swapped the MPU for a known good one and all the smaller molex connectors , for sound Switches, display & lamps) have been changed and re=pinned It is very odd as when switched on the 6 lamps affected are already on before the MPU boots. I am changing all the 1n 4004 diodes but they read fine when tested in situ.
 
Well I have changed all the diodes of the offending lamps but no joy! This problem defies all logic. I know it is not the MPU as I have changed it and the fault is exactly as before. I have checked continuity of the lamps and all are good back to the MPU i have run a new earth and signal leads between the PSU and the lamps I have changed all the diodes. What is really really odd is that if I enter test, all lamps flash as they should but when I boot the machine, as soon as I have flicked the switch, these 6 lamps come on until the machine boots then go off. They may come back of their own accord What else can it be? As it is not a Matrix individual lamps are triggered by thyristors so it points to the MPU but that has been changed Arrrggghhhhh!!
 
if you’ve replaced diodes and changed the main board, then it’s wiring. are those 6 lamps physically near each other, ie share the same common wire? what voltage do you get on that common wire compared to ground on both dc and ac meter measurements?
 
AlanJ said:
if you’ve replaced diodes and changed the main board, then it’s wiring. are those 6 lamps physically near each other, ie share the same common wire? what voltage do you get on that common wire compared to ground on both dc and ac meter measurements?
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I agree it points to the wiring and 6803 games are apparently notorious for breaks in the cables but I have run new wires direct from the PSU & MPU to the lamps in question and still they flicker, sometime they work, sometimes they dontWhat is really odd that I have run wires I 100% know it is not the MPU but what I dont understand is why upon switch on and before the machine boots do these 6 lamps come on? As soon as it boots they go off and sometime come on when they feel like it.
 
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AlanJ said:
are those 6 lamps physically near each other,
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^^^ @Game On have you considered this from Alan? If so are they on the same phase?

Game On said:
upon switch on and before the machine boots do these 6 lamps come on?
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Are these the only 6 lamps that light during that stage?

I had a biphase lamp problem on my Gold Ball (perhaps the first biphase machine?) and found it useful to t/shoot by jumping the appropriate 0A or 0B common from a close by fully working feature light on the same phase. This helped me track down an intermittent wiring problem.

This is an interesting head scratcher for us bystanders, following with interest good luck finding the fault :thumbs:

1643455516902.png
 
Game On said:
I agree it points to the wiring and 6803 games are apparently notorious for breaks in the cables but I have run new wires direct from the PSU & MPU to the lamps in question and still they flicker, sometime they work, sometimes they dontWhat is really odd that I have run wires I 100% know it is not the MPU but what I dont understand is why upon switch on and before the machine boots do these 6 lamps come on? As soon as it boots they go off and sometime come on when they feel like it.
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if they re going on s soon as machine powered on, then its either duff SCR's or a wiring problem, you ahve ruled out duff scr's by changing boards, so must be wiring - unless both boards have the same problem. You havent told us which 6 bulbs it is, - that could be crucial info??????
 
AlanJ said:
if they re going on s soon as machine powered on, then its either duff SCR's or a wiring problem, you ahve ruled out duff scr's by changing boards, so must be wiring - unless both boards have the same problem. You havent told us which 6 bulbs it is, - that could be crucial info??????
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It is most odd as I have swapped out the MPU and still it happens. I am 100% sure it has to be in the wiring or a duff diode somwhere. It affects both phases of J10 PIN 1, 7 & 16 but is left on for a while the offending lamps somtimes flicker or even come on which I guess rules out faulty diodes? it cannot be the power supply because all that does is come in from the transformer, through 2 fuses and then out again and the volts measure 11.5 volts AC stable I am beginning to think that somewhere on this game the 2 phases (Red & Black) have been swapped around as when I conduct an all lamps test everything is fine. I will find the barsteward fault and report back.
 
if it’s both phases of a single scr then that tells you a lot. i’d logic probe the gates of those scrs and the outputs - see that’s going on when it powers i then boots. do it with the j10 connected and disconnected
 
AlanJ said:
if it’s both phases of a single scr then that tells you a lot. i’d logic probe the gates of those scrs and the outputs - see that’s going on when it powers i then boots. do it with the j10 connected and disconnected
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Hi Alan normally I would agree with you. but I 100% know it is nothing to do with the MPU I know this because I have changed it, I put the ROMS in my original board and it works in my other game. As I have continuity tested the cables that run from J10 & 11 and they all show as OK I have also made up a lamp on 2 wires If I connect one to either phase of the PSU and go to all the pins of J10 apart from pin 16 that does have a blown SCR , (waiting on order) they all flash the lamp also when you go into the all lamp test, they all light but in the single tests the offending lamps do not. I am beginning to think there is a phase swap somewhere in the loom or another blown diode somewhere I will find this fault and get back to all interested.
 
Pudsey pinball said:
I’m hooked on the cause of this hope ya find it👍🏻
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I running all new cabling to the offending lamps. I am also now changing the molex connector on the power board. I know this sound desparate and defies logic as there are other lamps full working using the same feed. The real puzzle is why when in the "all lamps" test thy all work fine. This is a real mystery to me but I am going to find the fkr I will update progress
 
Game On said:
It affects both phases of J10 PIN 1, 7 & 16
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Based on the names of the lamps driven by these pins (Weapon values on 0A and Bonus values on 0B) it sounds like they're physically close togethor, if so that's suspicious. I'd be tempted to fully disconnect the 6 sockets from their voltage Red or Black feed then jumper each to a known good appropriate feed on a close "good" feature lamp.
 
AlanJ said:
If the lamps are getting their power from a DC source instead of one of the AC phases, that would cause the issue.
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Good thinking. I have rund totally new cables to one of the offending lamps and whilst connecting I accidentally shorted the feed to eart and blew the SCR so smitrhereens. Luckily I have more on order. I will try your suggestion thank you
 
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