Common cause of jail bars?

[big10p]

I'm getting intermittent jail bars on some graphics and wondered if there's a most likely cause? It's a 3 layer board so its difficult to make sure all socketed chips are seated properly, but I will take it apart and do that. Anything else to check for?

I knew it was a bad idea to start buying original PCBs instead of sticking with emulation. Lol

 

[Jacmar]

Can you put up a picture of the problem ?

 

[big10p]

Can you put up a picture of the problem ?

Seems to be on the sprites. Also just noticed player ship colour is wrong, I think.


And here the lines in A and B area symbols. Also some garbage lines/dots constantly displaying on left of screen.

 

[sukhbir]

Possible line buffer sprite rams.

 

[big10p]

Possible line buffer sprite rams.

Do you know where these are on the PCBs?

 

[Jacmar]

Yes ram issues often cause horizontal lines like that. Need (decent quality) pics of the PCB to identify what likely does what. What game is it ?

 

[big10p]

Yes ram issues often cause horizontal lines like that. Need (decent quality) pics of the PCB to identify what likely does what. What game is it ?

It's an original Tehkan Star Force. Just bought it as fully working.

I'll post a pic of all 3 boards when I can. I did notice the board has some trace wires so presumably has been fixed in the past.

 

[sukhbir]

If it's the bottom board (video)with trace wires then that's how it left the factory.
this board set is a pain to work on,I think the middle board is where the graphics roms are held.

 

[Lurch666]

Try reseating the cables connecting the boards.

 

[big10p]

Try reseating the cables connecting the boards.

I did make sure they're all plugged in properly but will have a closer look at them when I dismantle it.

 

[Georgian2]

3 layers boards need a lot of curent. Is 5V good enough on all PCBs?

 

[big10p]

3 layers boards need a lot of curent. Is 5V good enough on all PCBs?

It's at just slightly over 5v according to my supergun, but I haven't checked on individual boards. I'll do that, thanks. I did consider trying to up the voltage but the 12v rail is already at 13v and I didn't want to blow something by turning it up.

 

[Jacmar]

I'm pretty sure your audio amp is the only thing connected to 12v and will be rated up to 16/18v if not even higher?
Someone more knowledgeable than me can confirm that though!

 

[sukhbir]

Yep the +12 volts is not a concern as most arcade amps can handle +18 volts Max.
The +5 volts is more important and should be kept at that voltage and measured on the jamma edge on the arcade pcb,too much and the chips will eventually cook.

 

[big10p]

Thanks for the info, guys. I just checked the voltages on the actual boards and it's dropping down to 4.5v on the bottom board!

I turned up the voltage to 5.2v at the edge connector and that's giving me 4.8v on the bottom board. This seems to have sorted the jail bar issue, but I will test further tomorrow and try getting the voltage up to 5v on the bottom board, now I know it's ok for the 12v rail to go higher. 👍

 

[Georgian2]

My advise to anyone who wants to swap games often and play them is to use emulation. You can't really have an plug and play universal cab that works with all games without adjustments. There is always something to adjust. Always. PCBs are best played in an single cab.

 

[big10p]

My advise to anyone who wants to swap games often and play them is to use emulation. You can't really have an plug and play universal cab that works with all games without adjustments. There is always something to adjust. Always. PCBs are best played in an single cab.

I intend to have the few boards I've bought installed in cabs. I'm just testing they work ok using a supergun. I've bought a couple of 2-way JAMMA switchers to hopefully have 2 boards installed in a couple of cabs, but haven't tried them yet so we have to see how well that goes. 🙂

 

[Georgian2]

I intend to have the few boards I've bought installed in cabs. I'm just testing they work ok using a supergun. I've bought a couple of 2-way JAMMA switchers to hopefully have 2 boards installed in a couple of cabs, but haven't tried them yet so we have to see how well that goes. 🙂

You must find 2 games that draw the same amount of power. This way, your voltage will be stable and can easly switch between games.
This depends on the switcher used. I have one that powers both games same time and only switch the rgb and other signals.

I don't like other switchers because there are spikes when switching between games. You remove the load and put it back on quickly when switching. Good ATX power supplys should be fine with it but older ones may swing.

Of course many of you don't like the ideea of having an unused game powerd all the time

 

[big10p]

You must find 2 games that draw the same amount of power. This way, your voltage will be stable and can easly switch between games.
This depends on the switcher used. I have one that powers both games same time and only switch the rgb and other signals.

I don't like other switchers because there are spikes when switching between games. You remove the load and put it back on quickly when switching. Good ATX power supplys should be fine with it but older ones may swing.

Of course many of you don't like the ideea of having an unused game powerd all the time

Mine only power one board at a time but I will be checking voltages when I set them up with boards, and I won't be changing between games too often, I doubt. But yeah, I'll just have to see how things work out.

 

[Georgian2]

Mine only power one board at a time but I will be checking voltages when I set them up with boards, and I won't be changing between games too often, I doubt. But yeah, I'll just have to see how things work out.

I once had an dream of building two arcade towers. One for horizontal games and one for vertical. Like one rack with 10 slots for PCBs. Each slot with own power supply and so on ) it turned out to be way to much work and could't find anybody to build the racks.