Williams joust PCB: cmos RAM error or write protect failure

[baritonomarc]

Williams joust PCB: cmos RAM error or write protect failure

Hi all,

i am trying to repair a Joust PCB. When i turn on the machine, i have the splash screen (rug pattern), then the message "INITIAL TESTS INDICATE ALL SYSTEMS GO" and i can see for less than a second the "DAILY BUZZARDS" screen. I have the "zero" displayed on the ROM board. Then the PCB resets...

I read that sometimes resets are due to a non optimal voltage supply, but i gave a check to the range my PSU can supply and nothing changes varying that from 4.8 to 5.4 V

When i perform an "advance" test, ROM and RAM tests pass, but the CMOS test reports "cmos RAM error or write protect failure... what could it be?

Consider that i have recently placed a CR2032 lithium battery substituting the original alkaline holder and that the machine is switching supplied (i have not the original power unit).

Thanks for the help

 

[enjoyvelvet]

You want to go back to the original power supply. The switching power supplies are known to cause errors. Have you done the nvram conversion since you have a switcher in there?

 

[baritonomarc]

I think hte original PS is toasted. I will see for the NVRAM convertion, thanks!

 

[YellowDog]

The switcher might contribute to resetting the CMOS settings, but it should not cause the MPU board to reset. That sounds more like an issue with the watchdog circuit resetting the board. This can be caused by a number of problems that can usually only be resolved with a logic probe and a lot of patience.

Most common among the issues:
(1) Bad ROM images. This can be either one or more bad ROM chips or mismatched versions.
(2) Bad special chips. When the game play begins, most Williams games give a command to the special chips (just custom bitter chips) to clear the screen. If the chips are bad or the sockets are bad, the chips won't fire and the watchdog will reset the boards.
(3) Addressing chip failures. These are normally caught during the RAM/ROM tests, but have been known to cause random reboots.
(4) The watchdog circuit. The WD is reset by having a specific memory address written to with a specific bit pattern. If the addresssing chips that decode this and reset the WD counter are bad, the WD will not get reset and will in turn reset the boards.

There are a number of documents out on the net describing how to debug the watchdog circuit using a logic probe and/or oscilliscope,

ken

 

[YellowDog]

I think hte original PS is toasted. I will see for the NVRAM convertion, thanks!

NVRAM will probably not help in this situation. NVRAM is just used in place of the CMOS RAM to hold settings and high scores and will eliminate the need for putting batteries in until it needs to be replaced (when its internal battery is depleted). Most NVRAM solutions appear to be just as subect to corruption as the CMOS is.

It sounds like your boardset is just having trouble getting the game started after the POST (Power On Self Test).

ken

 

[retroACTIVE]

Hi all,

i am trying to repair a Joust PCB. When i turn on the machine, i have the splash screen (rug pattern), then the message "INITIAL TESTS INDICATE ALL SYSTEMS GO" and i can see for less than a second the "DAILY BUZZARDS" screen. I have the "zero" displayed on the ROM board. Then the PCB resets...

I read that sometimes resets are due to a non optimal voltage supply, but i gave a check to the range my PSU can supply and nothing changes varying that from 4.8 to 5.4 V

When i perform an "advance" test, ROM and RAM tests pass, but the CMOS test reports "cmos RAM error or write protect failure... what could it be?

Consider that i have recently placed a CR2032 lithium battery substituting the original alkaline holder and that the machine is switching supplied (i have not the original power unit).

Thanks for the help

Robotron/Joust/Sinistar are not as sensitive to the switcher as Defender (they use different CMOS circuitry and a different CMOS RAM all together).

Write protect failure means the CPU cannot select the chip for writing or reading. If its a fault then either the chip is bad or the chip select logic is bad. However, it could be that the CPU thinks the coin door is open.. there is a lock-out switch on the coin door/cash box which basically write protects the CMOS RAM... this signal can prohibit the CPU from writing to the device.

Yes the original PS is better than a switcher... however once the board is up and running you should be able to go through the tests just fine.

 

[YellowDog]

When i perform an "advance" test, ROM and RAM tests pass, but the CMOS test reports "cmos RAM error or write protect failure... what could it be?

There are several possibilites for the CMOS error.
(1) the CMOS is indeed bad and needs to be replaced.
(2) the memory protect switch (front left side of the coin door) might be bad.
(3) the chips that sense the memory protect switch might be bad.

ken

 

[baritonomarc]

Thank you all

is it possible that a ROM is not ok, even if the initial test reports no ROM errors? Because the test passes with this board
how can i test the watch dog circuit? Where is it located (sorry for the newby question)
The lock out switch you refer to, retroACTIVE, is the IJ2 connector (memory protect interlock)? I have it grounded when the coin door is closed, open when the coin door is opened... is it correct (i made the harness myself because the machine had all the cables cut)?

 

[retroACTIVE]

Thank you all
The lock out switch you refer to, retroACTIVE, is the IJ2 connector (memory protect interlock)? I have it grounded when the coin door is closed, open when the coin door is opened... is it correct (i made the harness myself because the machine had all the cables cut)?

Yes that is the switch but I think you want it the other way... not sure, I don't have my schematics w/me.

Disconnect it and try the test again... see what goes.

 

[YellowDog]

Thank you all

is it possible that a ROM is not ok, even if the initial test reports no ROM errors? Because the test passes with this board
how can i test the watch dog circuit? Where is it located (sorry for the newby question)
The lock out switch you refer to, retroACTIVE, is the IJ2 connector (memory protect interlock)? I have it grounded when the coin door is closed, open when the coin door is opened... is it correct (i made the harness myself because the machine had all the cables cut)?

That should be the right way. When I am testing boards I don't have anything plugged in (which would correspond to the coin door open).

ken

 

[baritonomarc]

There are several possibilites for the CMOS error.
(1) the CMOS is indeed bad and needs to be replaced.
(2) the memory protect switch (front left side of the coin door) might be bad.
(3) the chips that sense the memory protect switch might be bad.

ken

Is the CMOS chip still produced/available? I was planning to substitute it since my board still doesn't work. I am planning to substitute the D10 diode, also, because i read that vcauses multiple problems if defective... could it affect my board giving reboots?

thanks very much

 

[YellowDog]

The 5116 is pretty much an extinct chip. The 6116 is an acceptable substitute. You can get them from several chip vendors. I normally get them from GPE (link) because I order from Ed about once a month anyway.

ken

 

[baritonomarc]

Thank you very much Ken

 

[baritonomarc]

Yesterday i substituted the D10 diode, but the PCB still have reboots... I had no luck finding out a new CMOS RAM in local stores, so i will buy one on the net (PS: is the IDT6116A25TP or the CDM6116AE3 the right one?).

Just to know, where the chips that sense the memory protect switch are located in the board? Could reseating those socket chips i can see (from 1K to 3R) help solving this reset problem?

Thanks

EDIT: i wanna add an info, just because probably can help PCB guru's formulate an hypotesis to face the problems of my board: when i access to the bookeeping totals menu (advance mode) a couple of voices (if i remember well "total single player" and "total dual player") both reports "110011" wich feels so "binary" to me... maybe a coincidence, but could it be due to something faulty (apart from 110011 games played) ?

 

[YellowDog]

Here is the datasheet (courtesy of Jameco Electronics) https://www.jameco.com/Jameco/Products/ProdDS/42809.pdf

The memory protect circuit consists of several ICs any of which could have gone bad. The most common one is at 6E which takes the signal from the memory protect switch. This feeds 6I which feeds the CMOS chip and is also fed by 5K and the clock pulse from 7G. Unless your board has beed repaired sometiime in the past, those chips will not be socketed. You would also need to use a logic probe to determine which of the chips is not acting correctly.

ken

 

[baritonomarc]

Thank you very much, your help is much appreciated here . I am trying to "grow" in the field of PCB troubleshooting and your suggestions are helping me a lot. After being able to face a bad ROM problem (very easy indeed with an EPROM reader/writer), it looks like my next step is to learn how to see if a chip is bad... can you suggest me some (easy) thread/link i can study for this pourpouse? I know how a logic probe works, but dont know how to use it effectively

 

[andykmv]

Thank you very much, your help is much appreciated here . I am trying to "grow" in the field of PCB troubleshooting and your suggestions are helping me a lot. After being able to face a bad ROM problem (very easy indeed with an EPROM reader/writer), it looks like my next step is to learn how to see if a chip is bad... can you suggest me some (easy) thread/link i can study for this pourpouse? I know how a logic probe works, but dont know how to use it effectively

some links
http://www.izabella.freeuk.com/html/fault_finding.html
http://talkingelectronics.com/projects/LogicProbe/Logic Probe with Pulser_03-Using Probe.html
http://www.electronics-project-design.com/LogicProbe.html
http://www.siliconchip.com.au/cms/A_102204/article.html
http://kitsrus.com/projects/k24.pdf
http://www.wisc-online.com/objects/ViewObject.aspx?ID=DIG2403
http://www.experts-exchange.com/Hardware/Misc/Q_10036550.html

some general suggestions:
study up on the ics used.
collect pdf copies of the datasheets for all ICs used in the various boards on your game CPU, Widget/IO, ROM, Sound and Power Supply PCBs. study what each of the ICs do and their specifications.

study wot the TTL (transistor transistor logic) standard is all about.
understanding TTL logic will help you to understand the importance of stable power supplies operating within certain parameters, and, why circuits play up when under supplied

learn to use your tools.
if your multimeter has a frequency measurement setting, probe the game circuits and see signalling frequencies you can see - video sync circuits, system clocks etc. careful you dont short anything out.

maybe with the logic probe, start with low repetition circuits like the game button and joystick inputs on the widget or io boards and see how the logic probe responds to High to low transisitons , low to high transistions and repetitious transitions on CMOS or TTL circuits, and look at signals like the E clock from the main processor that appears across the boards

 

[HudsonArcade]

The 5116 is pretty much an extinct chip. The 6116 is an acceptable substitute. You can get them from several chip vendors. I normally get them from GPE (link) because I order from Ed about once a month anyway.

ken

The cmos is a 5114, not a 5116. 6116 won't work...

5114 is 1kx4, like a 2114, in an 18-pin dip.
6116 is 2kx8 in a 24-pin dip.

6514 will work if you can find it...

Good thing people sell adapter boards to put NVRAM or BRAM in place of 5114s in williams games

 

[baritonomarc]

Thanks HudsonArcade for the advice

Yesterday i had the idea (i have not a logic probe ATM, so iam trying to debug the machine with some common sense ) to leave the machine turned on for 10 minutes... after something like 15-20 reboot, i had a messy "daily buzzards" image, then the joust logo appeared O_O... the image was not 100% ok because instead of the "presented by williams electronics inc" blu string, i had something like "GGGGGGGGGFFFFFFFFFFFFFFFHHHHHHHHHH"... could this be of any help to face the prob? I wanna remind that my EPROM reader reported all good ROM images... could it be that one of those is NOT so good?

Notice that i tryied to switch off the machine, but when i turned it on i had again the reboots and, again, i was able to play after lots of reboots... so, not something related to juicing and then heating up the PCB, i suppose.

Ah, and when i ended the game (that had some issue on collecting points and was givin random extra lives), on the daily buzzards screen i had again reboots.

Making some step further every day here

 

[andykmv]

... the image was not 100% ok because instead of the "presented by williams electronics inc" blu string, i had something like "GGGGGGGGGFFFFFFFFFFFFFFFHHHHHHHHHH"... could this be of any help to face the prob? I wanna remind that my EPROM reader reported all good ROM images... could it be that one of those is NOT so good?...

possible. but could be bad rom socket(s)...