Midway Space Invaders issue

Talon2000

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I've got an SI I'm trying to work on. Had 4 proms, and booted to a garbage screen.

Re-strapped the board for 2716, and put in my test rom. It displays nothing but horizontal lines.

space%20invaders%20001.jpg


Power supply is known good, (I'm using my SID cab)

Checked and cleaned edge connector interconnect. Probably something easy I'm missing, but the old brain is drained from finishing up the Omega Race repairs today.
 
Were the proms 9316B's? And if so are you using 2716s and NOT Tms-2716's? If you're using regular 2716's I was under the impression they are drop in replacements for 9316b.
 
Were the proms 9316B's? And if so are you using 2716s and NOT Tms-2716's? If you're using regular 2716's I was under the impression they are drop in replacements for 9316b.

They are a drop in replacement. If you strapped the board for TMS2716, I'd imagine the regular 2716 would pretty much be shot. I'd set it back up for the PROMs and put in a standard 2716 (or 2732 with the code doubled) and give it another shot.

Then again... don't quote me on anything, ever.
 
Incidentally you'll get those horizontal/vertical bars when there's no roms installed in socket H. Thats why I asked :) If you have thin and fat bars, try contacting the slam switch. If they change patterns, supposedly thats good, although the board I have did the same thing and still didn't work with fresh roms (I think it needs new sockets).
 
Yeah- those bars look good except for maybe the small gap in them.

The writeup says you can ground pin 7 of each RAM to find a bad row.

I've been trying this with mine. When you ground the pin (or pull high one of the corresponding pins at chip C4), one of the thin lines will 'fill in'. That should narrow down which row of RAM has a bad chip.

My lines look nothing like yours. I get the 16 repeating sets of bars, but my bars are all garbled and not solid.

I agree that since you're getting to the RAM display, the board is not reading anything from the EPROM. Replace that socket and keep trying. Recheck that test ROM if you think it got zapped.

Kerry
 
Were the proms 9316B's? And if so are you using 2716s and NOT Tms-2716's? If you're using regular 2716's I was under the impression they are drop in replacements for 9316b.

9316B = regular 2716.....not always.

Sometimes a regular 2716 will not work with the 9316B strapping....sometimes it will. The strapping is actually different between those two chips.....well, one jumper is. I can't remember which jumper it is....and my notes arn't with me (and I don't feel like pulling schematic pdf's and figuering it out at the monent :)

I can tell you from experience.....some manufacturers regular 2716's will work with the 9316B strapping, some will not. And of course, the bastard that is a TMS2716 is a totally different beast. Midway released a service bulletin on this. Here you go...page 83.
http://arcarc.xmission.com/PDF_Misc/Midway Service Notes 1.pdf

It also should be noted.....not all motherboards are the same. The older revisions require a bit of hacking to even be able to use a regular 2716. Midway released a service bulletin on this also. Page 87 from same link above.

Edward
 
So is there any rule of thumb here as far as when the board requires the hacking, when it will not, etc etc? Every time this topic comes up the words sometimes...maybe..not sure...always comes up lol :)
 
Thanks for the good info.

I'm using Intel 2716, it had the 9316 chips in it. 4 of them.

I went by the schematics avail, which shows jumpers for the 9316, and a 2716.

So I had actually tried the 2716, which as I'm now understanding is for the TMS2716 chips, and that the 9316 should work with most 2716 chip?

Also good to know that the lines means it's not seeing roms. I'll do some more playing around this evening, with both TMS non TMS, and the like.

Thanks
 
Thanks for the good info.

I'm using Intel 2716, it had the 9316 chips in it. 4 of them.

I went by the schematics avail, which shows jumpers for the 9316, and a 2716.

So I had actually tried the 2716, which as I'm now understanding is for the TMS2716 chips, and that the 9316 should work with most 2716 chip?

Also good to know that the lines means it's not seeing roms. I'll do some more playing around this evening, with both TMS non TMS, and the like.

Thanks

If you plugged "regular"2716's into a socket strapped for TMS2716.....the odds are very good you killed your 2716's. Toss them in the garbage and start over.

Edward
 
So is there any rule of thumb here as far as when the board requires the hacking, when it will not, etc etc? Every time this topic comes up the words sometimes...maybe..not sure...always comes up lol :)

Alright, I dug out my notes and schematics....When using 9316B, jumper S2 is connected to ground. When using regular 2716's.....jumper S2 is connnected to +5VDC. All other jumpers are the same between these two chips. This all assumes you have one of the later revisions of the motherboard. Now, do you have an older revision?...or newer. Midway made a ton of revisions on these 8080A motherboards. There should be etching numbers on them...something like 80-900D, 80-900E, 80-900F, etc.....at some point they changed their numbering to something like A080-90000-H000, A080-90000-K000, A080-90000-L000, etc.

At one point a major revision was done....basically, early boards have jumper S5 connected to pin 18 of the ROMs. On later boards, jumper S5 goes to pin 20 of the ROMs. Obviously, this causes problems depending on what ROMs you're using.

I could go on and make this even more confusing...:)

Edward
 
Well I'm at work currently so I can't tell you what Rev the board is.

However my Rom is still good, It's looking like a socket problem. Didn't get much of a chance to work on it last night.

So S2 going from Gnd to +5 is the only difference (provided I have the correct Rev MB) when switching from 9316 to 2716. If mixing 9316 and 2716 pull pin 21 of the 2716 and short it to pin 24 +5.

I could have sworn there was another jumper to move AD10 or 9 forget which, or is that the same on the 9316 as the 2716. Someone should publish a book. lol
 
The board is a SI, it's just in a SID cab. But I'm just trying to get a 2716 test rom running so it shouldn't matter.

Ok so my board is a 80-900K So is that older or newer. I assume later since S5 goes to pin 20.

S2 which goes to pin 21 is connected to the +5 line.

Socket is new, and I've ohm'd out all the pins, they check good.

Same picture.

So I tried putting s5 on pin 18.

Same thing.

So At this point I'm thinking it's an Address bus, or Data bus problem. That sound about right?
 
Just get the pinout for the rom and test each line with a logic probe to see what happens. May be possible the CPU needs a new socket or cleaning.
 
For what it's worth, with (presumably) a newer board that originally had 9316's, a 2716 was a drop in replacement. No mods needed, S2 going to ground from factory.
 
For what it's worth, with (presumably) a newer board that originally had 9316's, a 2716 was a drop in replacement. No mods needed, S2 going to ground from factory.

I have no idea why....but.....some 2716s will work with the 9316 strapping, and some won't.

Edward
 
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