Midway clowns and 2716's

wrongdon

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I'm just kind of thinking out loud again,but feel free to chime in.I am working on a midway clowns pcb.Game would just boot to a pattern scrolling up and down the screen,so i booted it in test mode and it did the same pattern for a few seconds and then said H.I figured rom H,so i pulled and reseated,no change.Figured i would burn a new one,except they are masked roms and the board calls for 2708's.So i found this page here
http://www.marvin3m.com/video/seawolf.htm
And proceeded to strap the board for 2716's.So I used copy /b and combined H+G , F+E and D+C and burned 3 2716's,this just gave me the same pattern in test and game mode and i didn't get the H.Ok that may not have been the right thing to do,so i burned the roms individually on 6 2716's.Just lines on the screen and coining it up just changes the pattern slightly.
Currently roms are erasing ,tomorrow is another day.
After strapping pin 21 goes to +5 so they should read.
Now i am wondering If maybe i grouped the roms wrong or if i need to do something different with them before i burn them individually.I am just guessing that there should be some sort of message after it passes ram/rom test.
This should keep me out of trouble for a while.
 
Doing 6 individual roms prob won't work as I think after socket D the addresses change drastically. If you get the lines with no roms installed thats prob good - you should download the SI test rom to see if that does anything.

Take a picture of your strapping...then do some searching for my username and Space Invaders roms, you'll find all sorts of postings and info.

PS - if the thing your seeing scrolling kinda looks like a windowshade going up and down...then you either have the roms not paired right or not in the right order. Its a rom problem is what I'm tryin to say.

Last but not least - rom sockets and cpu socket should be replaced on these things.
 
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I just burned and tried the space invaders test rom and it actually helped some.Some patterns appear on the screen and then the diagnostic page comes up.all the ram is good and i can press either button or coin switch and see it register on the inputs.I can't do much else as i have no joysticks,just a couple of spinners.But in any case,it boots to the test rom and i have maybe 3 seconds to look at the diagnostic screen,the coin counter clicks and it resets.
I will follow your advice more tomorrow,i am really going to call it a night this time.
 
Here is my strapping,all i can think is S6 could be wrong.
The smaller jump at S2 does not touch the longer 2 traces,it jumps over them and ends to the left of the other jumper.I'll replace the sockets later today.
 

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S6 is wrong - the 3 towards the top of the pic should go to the 3 holes to the farthest right on the bottom row. Make sure they connect as it looks like the pads got lifted. Thats your rom problem right there.

Like this:

....O O O
......\ \ \
O O O O O

S6 determines the layout of the addresses across the rom sockets...the way it sits (i'm not 100% sure) thats probably set up for the 6 2708s, where after 8kbits its jumping to the next socket instead of continuing on the existing socket for another 8kbit. Make sense? I'll have to look at a board here to compare the other jumpering but if the test rom at least booted and didn't go up in smoke chances are its ok.
 
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Yea i hear ya on the 2 a.m. But i have a hard time walking away from a project,even if it is for sleep.All sockets are pin to pin,as in they all have continuity except for pin 20 ,chip enable ? it is unique to each socket.So i may need to put H+G in H , F+E in F and D+C in D.
Thank you for all your help.
 
Read my post again I updated it - your S6 is wrong, and thats also why I'm up at 2am. Thank god I can work from home once in a while.

Pin 20 is chip enable - thats connected to the chip next to S6. S6 are the 3 top address lines, they go to that chip next to them that decodes them and then runs the chip enables for each rom socket, hence why S6 determines the layout of the rom sockets.
 
Excellent,i will get right on it.

S6 is wrong - the 3 towards the top of the pic should go to the 3 holes to the farthest right on the bottom row. Make sure they connect as it looks like the pads got lifted. Thats your rom problem right there.

Like this:

....O O O
......\ \ \
O O O O O

S6 determines the layout of the addresses across the rom sockets...the way it sits (i'm not 100% sure) thats probably set up for the 6 2708s, where after 8kbits its jumping to the next socket instead of continuing on the existing socket for another 8kbit. Make sense? I'll have to look at a board here to compare the other jumpering but if the test rom at least booted and didn't go up in smoke chances are its ok.
 
I changed S6 as pictured and the results are the same,curtain going up and down.I tried roms at locations D,F and G as well as E,F,G.I got some running to do so maybe i'll get a fresh perspective when i get back.I'm leaning towards burning them wrong.Do you group them in order like that,H and G into one rom and such.
 
If I were to try a wierd rom placement, I'd do H, G, and D if anything. It starts with H and goes backwards. Next time I run to the basement I'll check a board and look at the rest of the strapping. What you can also do if you have a logic probe is check pin 20 on the first 3 sockets (H, G, F) to see if you get activity.

Remember that the rom sockets are very prone to failure, if they're original you may have everything right and thats why it still not working.

I think the grouping works as long as you use /b. Only way it might not work is if the 2708 configuration was a high/low bit thing where the roms need to be interleaved instead of stacked, but I dont think these boards work that way.
 
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Other strapping looks wrong too...here's how I do it, and this works for every board I've worked on that has a 2716 (or a 2764 with modded socket adapter).
 

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Do yourself a favor and strap it for a single rom 27128, so you can run *any* game on it.

Hmmmm,What other games would run on this particular hardware ? I just have player one and two start and two spinners,well,more like paddles.That would be a neat idea..

I will break out the logic probe in a bit and check activity on pin 20.
 
The daughterboard kinda dictates what game it can actually run, but supposedly some can run others, I'm just not sure whats what.

Anyhow, before you bother with the logic probe - update the strapping first, especially S2 and see if that works. Once you update it, put the 3 roms back in H, G and F.
 
Other strapping looks wrong too...here's how I do it, and this works for every board I've worked on that has a 2716 (or a 2764 with modded socket adapter).

Got it all jumpered as you described.And now i get a pattern of garbage on the screen,and it does up like the curtain,then stays that way with some thin white lines.The activity on pin 20 on every socket is the same,all high.
I'm gonna beat this yet.
 
Rom sockets were the culprit in the end.I put them in , didn't hold my breath and then it came up i about died.Now to clean the controls as they are jumpy,and figure out what all the pots are for on the daughter board.Maybe sensitivity or something.
Thanks so much for your help,now i can get on with cleaning it up and seeing what else it needs.
 
Congrats! Yeah I knew once we corrected the strapping there was still a rom problem somewhere.

Pots on daughterboard are most likely volume controls for each individual sound if there's many.
 
Hi
Working on bringing back to life my Clowns project (sitting for quite some time) and finally got the board to fire up with all voltages applied.
I am using a switching adapter and the P/S was shutting down due to a short on the daughter PCB. Found a bad Tant cap, replaced with an electrolytic and now get to continue.
Was getting the up and down "window shade" so pulled and replaced all 6 X EPROM and 1 X CPU sockets but still have the same display.
I am thinking of swapping the EPROMs to 2716's but are a bit leery of modifying the PCB strapping, specifically as shown in pic "strap2" in post #4.
Would it be possible for a better picture of that while strapped for the 2716's?
Thank you
Jeff
 
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