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Title: Identifying Unknown Boards Post by: lesoleil70 on March 29, 2015, 05:00:27 pm I got this here :- https://www.mikesarcade.com/cgi-bin/spies.cgi?action=url&type=info&page=Identify-unknown-boards.txt (https://www.mikesarcade.com/cgi-bin/spies.cgi?action=url&type=info&page=Identify-unknown-boards.txt)
and thought it was so good , and to the point, I'd post it here. Newsgroups: rec.games.video.arcade.collecting From: rls@intgp8.ih.att.com (-Schieve,R.L.) Subject: Re: how do you find the +5,+12,-5 voltages on a board, don't have pinouts? Date: Sun, 31 Jul 1994 18:20:21 GMT In article <5i2SznW.bubsy@delphi.com>, <bubsy@delphi.com> wrote: >How do you find out which pins are which voltages on a board that you >have no pinouts for? >erik Here is an old posting of mine that many have seen but maybe some of the new people are interested: --------------------- I've had a fair amount of favorable comments to my first Tech Tip (I know it sounds corny) so I guess I'll continue to ramble on for a while. Again, this based on my own experience from hacking away trying to keep some of these old favorites alive. If you check out Steve Ozdemir's VAPS list you will see that I own a few of these monsters :-) I'm trying to cover the real basics here for those just getting started working on their own arcade type video games. More and more people seem to be catching on to the fact that it is not all that difficult to get a monitor (with isolation transformer), a DC power supply, a few controls, and a game logic board to make an old game work without it's cabinet. This is a little tough with vector graphics games like Asteroids but often very straight forward with raster games. Let me know if you are unsure of the difference between vector and raster graphics games and I'll send you some details. I also have a past posting in raster monitor basics I can send. Video games are often converted to play different video games and the original logic board set is removed by the machine's operator. Often you can find the logic board set for a game you really want (like from Bruce Atkinson's sale or one I may have eventually) but coming up with documentation is often difficult. The pinout archive that Jonathan Deitch puts together may help but you may find yourself with a logic board and no wiring (often called pinout) info. You can often figure it out for yourself on many board sets, but not all. The following works for many. Game logic board inputs include power and control panel inputs. Outputs include RGB and sync to the monitor plus speaker connections. Power inputs to the average game board include +5 for the TTL logic, usually +12 for sound, and sometimes -5 for certain chips. Some boards (like most Pacmans) have AC inputs and do the AC to DC on the logic board itself but I'm ruling them out for now. Most board sets will operate with just the +5. To determine where to connect the +5 and ground, just find a TTL chip. 14 pin chips will have +5 on pin 14 and ground on pin 7. 16 pin chips will have +5 on pin 16 and ground on pin 8. Either trace some paths or use an ohmmeter. Identify all the +5 and ground connections and get a power supply capable of 6 amps or so at +5 and connect it to the board. BTW, make yourself some kind of diagram to fill in to identify the connections as you go. The board should hopefully be cycling now. I use an oscilloscope to see what is happening now but suspect you could get by with a voltmeter if you had to. Anyway, start scoping out the pins you haven't identified as +5 or ground. They will fall into several categories. First, the control panel switches usually just ground the input of a TTL gate. When not grounded by a control panel switch the inputs are held high by something like a 10K resistor between the input and the +5 volt supply. So all pins that weren't directly connected to the +5 volts to the logic board that are now at +5 are probably inputs so mark your diagram. The only active connections at this point will be for the monitor. Most boards generate a negative composite sync operating at TTL levels so if you find a connection that looks like TTL signals it should be the sync. If there are two your game board uses multiple syncs and if you don't know how to deal with that I'll send you my past monitor posting. Again, most boards will just have one so mark your diagram with the sync connection. Assuming this is a color game there will be 3 other active pins that look about the same. No relatively clean TTL, but lots of activity in the 0 to 5 volt range. These should be the RGB connections to the monitor. Power the board down and connect the RGB and sync leads to your game monitor and turn it on. You may have the colors wrong but you should get a picture and you can rearrange the RGB leads until it looks right. Occasionally, the game may not come up and you might have to determine if you need -5 volts somewhere. This is more difficult as you really need some device books to see if some of the chips require -5. Often just unusual memory components or devices that keep the high score table working will need the -5. To identify the inputs, take a clip lead and start grounding the leads you had identified as inputs. Eventually you will find the credit input and once the game has credits you can find the start. Once you can start a game you can try the other inputs and see what it takes to move or shoot. Eventually, you can identify them all unless the game requires a track ball or a joystick that uses pots. Last is sound. Most boards drive a speaker directly while some need a separate amp. If there is a pot on the board, there is usually an audio amp on the board that needs +12 volt to run. Look at the as yet unidentified traces at the connector on the board. The ones with wider traces or that head over towards the pot or a heat synced chip by the pot will the +12 input. Often there will be an electrolytic capacitor across the +12 volts to ground so another clue is to look for a big cap with a rating of at least 12VDC. When you think you have the +12 input attach a +12 volt supply good for an amp or so and power everything up and start a game. Now look for some activity on leads that were not active before. Chances are you can attach a speaker between the pin you find and ground and sounds will come out :-) You should pretty well have everything identified now. Again, there are lots of exceptions for differences like multiple syncs, special voltage requirements, separate audio amps, or special input devices, but in my experience about 80% of the logic boards I've fooled with can be made to work as I've described. Any other suggestions would be appreciated, but no flames please as I burn easily ;-) Rick Schieve rls@intgp1.att.com From: musjndx@gsusgi2.gsu.edu (Jonathan N. Deitch) Newsgroups: rec.games.video.arcade.collecting Subject: Re: how do you find the +5,+12,-5 voltages on a board, don't have pinouts? Date: 31 Jul 1994 12:24:03 -0400 bubsy@delphi.com writes: >How do you find out which pins are which voltages on a board that you >have no pinouts for? Easy -- find a chip which uses one of the voltages (TTL, RAM, ROM, video,etc) and backtrace to the edge connectors. You can find video the same way by looking for video output transistors. There'll be three of them for the three color signals. - Jonathan -- musjndx@gsusgi2.gsu.edu | "I Hate it when I can't trust | Atlanta 1996 !! jdeitch@aol.com | my own technology!" - LaForge | Play Pinball !! jdeitch@gisatl.fidonet.org |-------------------------------------------------- --------------------------- "Thrills! Chills! Magic! Prizes!" -- Hurricane Gene Roddenberry, Isaac Asimov, Jim Henson, Dr. Seuss, Mel Blanc ... Sigh ... From: phkahler@saturn.acs.oakland.edu (Paul H. Kahler) Newsgroups: rec.games.video.arcade.collecting Subject: Re: Boards figuring out -5volt? Date: 24 Nov 1994 00:28:26 GMT In article <RE2UVyf.bubsy@delphi.com> bubsy@delphi.com writes: :) I have a significant ammount of boards that I just can't seem to get going :) I am thinking that they may need the -5volt to get running. But I can't :) quite figure a method for finding -5volt. I can find +12,+5 pretty easily :) but not -5. I don't want to screw anything up by hooking negative 5 to :) anything it shouldn't be. Help please. That's easy. Look for capacitors that have the + end connected to ground. The - end must belong to a negative supply or the cap would be in backwards. Trace that connection back to the edge connector. If you put -5v where it wants -12 you probably won't hurt anything, but if you put -12 where it needs -5 it will probably hurt something. Try -5 first. If you find that there are 2 different negative supplys then it will require a closer look. ___ __ _ _ _ | \ / \ | | | || | phkahler@oakland.edu Engineer/Programmer | _/| || || |_| || |__ " What makes someone care so much? |_| |_||_| \___/ |____) for things another man can just ignore. " -S.H. Title: Re: Identifying Unknown Boards Post by: knaagi on March 30, 2015, 05:13:02 am Very useful!
Good post. Thanks lesoleil! |