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Topics - Elgen

Pages: 1 [2]
16
ARCADE / Large EPROMs and programming algorithms?
« on: February 15, 2012, 09:12:45 AM »
Yo, hope some of you guys can enlighten me a bit on this matter...

I have an Top2005+, and anyone that tried TopWin6 (the software that comes with it) knows that it stinks...so I'm currently writing my in C# with LibUsbDotNet based on OpenSchemes brillant backward engineering work found here: 

http://openschemes.com/2010/04/29/turning-a-top2005-eprom-programmer-into-a-desktop-test-bench/

LibUsbDotNet: 
http://sourceforge.net/projects/libusbdotnet/

But as I don't know hoot about writing code for FPGAs (using ie VERILOG), I'm just using a simple bitstream designed for "bit-bashing" (the ictest.bit described in the article) and implementing all bitmanipulation, algorithms etc. in C#, just sending the raw pin assignments to the Top2005+.
This is ofcause not very fast, but I'm going for high flexibility and making it easy to support new EPROMs, TTLs, SRAMS, ect. rather than speed (it's not like I'm going to program 100+ roms on a daily basis...};-P).

(Don't worry, when I have something is just a little nicer than my current prototyping code, I'll publish a project on GoogleCode or something like that for all of you to enjoy };-P).

And now for the question:
Old/small EPROMs like 2716 are programmed with the classic algorithm which goes something like this:
1. Set programming pin to Vpp and chip-enable to disabled.
2. Set address and data pins to the desired values.
3. Enable chip-enable pin for 50ms.
4. Advance address and data values and goto 2. until whole EPROM is programmed.
5. Do a verify pass comparing the EPROM to the data file/buffer.

Then I look at data sheets for large/new EPROMs, say 272048, they only describe various kinds of fast algorithms.

But is it still possible to program these large EPROMs using the classic algorithm, even though it'll be very much slower (remember I go for flexibility and simplicity over speed)?

Google haven't been very helpful; hope you guys might be };-P

Thnx in advance...

17
ARCADE / Capcom Last Duel Bootleg Repair Log
« on: December 15, 2011, 10:41:07 PM »
This board, a bootleg of Capcoms Last Duel (a vertical shooter with the subtitle "Inter Planet War 2012"; so ofcause I HAD to get it fixed before entering the new year };-P), I got in the same batch as Missing in Action and Fighting Soccer. The hardware is pretty standard and consists of two PCBs connected with ribbons.


When first plugged in, what I saw was this:

(a screen filled with garble...or so I thougth, but more on that later...)

I started by piggybacking the SRAMs on the primary PCB


and when doing so on an 6116, I got this screen; certainly a change.


But when desoldring, it tested good in the Top2005+, so it went back in.


It was then I discovered, that when doing a continuity test between +5V and GND on the egde connector, I got a beep. Switching to Ohms on the multimeter I saw that the impedance was about 50Ohms. That somehow didn't seem rigth, and I spend most of an evening trying to find out what was shortening the two. That included inspecting the many former repairs done on the main PCB (or maby just a consequence of it being a bootleg; the pics below shows only some of them). I desided on removing and redoing them one by one, each time trying to boot the board when they were off. But it didn't change a thing.




It was then I got the brilliant idea of trying to do the same continuity test on some working boards, and found that at least 2 of the 4 boards I tried had less than 70Ohms of impedance between +5V and GND. I then stopped chasing that ghost...
But now suddenly the screen looked VERY diffenrent (sadly I didn't catch a pic of it). Turning the board around and inspecting it, I saw that the reset-pin had been knocked off the main CPU, mainly because of the cap that was soldered onto it.


Here the damage is seen with the very simple bootstrap-circuit removed.


Mainly inspired by this rep log by Womble where he fixes a custom SMD IC with knocked of pins, I dug up my Dremel and started carving my way through the casing of the 68000.


Switched to a carving head a little less rough when I got close to the track.


And finally I found shiny metal };-D


soldered a wire on, and fastened it with drops of SuperGlue.


And this is the final result with the bootstrap circuit back in place. Now I had the usual screen of gable; ie status quo };-S
It was then I discovered, that this was NOT just a screen full of garble (try and have a scoll up and look at pic2 again!); this was actually the initial self-test booting up and trying to communicate with me. It reads: "WORK RAM : OK" and the next line was: "V R A M : NO GOOD". Aha! now I had something.


So flipped the board around to look at the SRAMS in graphics section. This is two of the SRAMS on the secondary PCB, and if you have a look just to the left of them, you see 2 usual suspects...Fujitsus (the two 245).


After a quick inspection I found that the secondary PCB had 9 Fujitsu-245 all in all. As I just happend to actually have a tube of TexasInstruments equivalents, I desided to desolder them all, fit sockets, and install new ones.


They all tested good except for number 3 from the left in the pic above.


and having a closer look, it didn't look good (notice the white "thing" on the right half of it...it looked like it had been very hot at some point).


After having installed all new TexasInstrument-IC's, the self test wrote "V R A M : OK" aaaaaand...


The board booted up! };-D




(Here are the 9 Fujitsus ready for the bin.)


The next problem to adress was: No sound! I tried the "finger test" on the amp, but there was not even a small hiss from the speakers. So googled the pinout for the amp; and hit the output (1) with the scope probe...


...and saw this (pic below). Now this looked alot like sound to me. So chased the signal downstream til the cap marked with 2, and found the signal at the other side as well. From there it went back to the amp (either feedback or bootstrap; can't remember which), but also to the cap marked with 3. When hitting the other side of that cap with the scope, I got a total flat-line.


Replaced the cap with a new one, and it brougth back sound.


Now the board was all good to go. So I connected the 2 PCBs with the legs again, I hooked up my SuperGun/testbench to my vertical tv for a test game, and then Johannes aka Elgees[2] woke up and needed my comfort....
After about 30minutes of constant singing and comforting, I returned and saw that I had left the game running. But sadly it wasn't running anymore. The screen that met was the one below, and it was frozen };-S


Turned the power off and on again and got this: "SCROLL 2 : NO GOOD".


Now I didn't know where to find the scroll2-RAM, so I grapped my "poker" (that is what I call this little simple but very handy tool; home-made from an old multimeter probe and a crocodile clip. You attach the clip to either +5V or GND and is then very easily capable of pulling different enable-pins on ICs high or low.)...


...and found the scroll2 was the two SRAMs to the left in the pic below. By accidently pressing down on the PCB in that area, I also saw, that I could provoke the scroll2-error in the self-test. So off the legs went again (moan!).


It seemed I'd been a bit too hasty, when replacing them 245's with sockets, as I'd forgotten to solder one of the pins. Fired up the iron, soldered the pin, and the scroll2-error was gone even if I pressed down on the PCB. One more board taken out of it's coma };-)


The game is actually a quite nice shmup once you get past the first stage, so I finish off this log with some pics from stage2, which has some really nice graphics; enjoy! };-P


18
ARCADE / Taito Double Dragon Bootleg Repair Log
« on: November 22, 2011, 09:12:33 PM »
This game is a true 80's classic (well at least around Roskilde, Denmark where I grew up). Back then almost all of my arcade gaming was done at burger joints with names like: Torvegrillen, Burger Place, Burger Boss, and Wopsi Burger. The latter was the best as it had 10+ standard cabinets with games changing about once a month...

Well enough nostalgia for this post; I proudly present (a bootleg of): Double Dragon!
I bought this just a few days ago, and by the symptoms it looked like an easy fix, so I started right away. A self test looking like this is always a good sign.


...but then trouble started. An intro screen looking like this:


Also the sprites where pretty messed up with stripes through them and some parts misplaced:


And the game had no sound at all!
Well easy to see that these two cabs in the sound section had seen better days


and not all that surprisingly, changing them brougth the sound back };-)


The board had some other obvious physical damages that needed fixing.
Here a knocked-off smoothening cap




1 transistor with 2 pins ripped off and the other one missing all together




A physically broken 157; the 04 just beside it had also taken a big knock at some point and was replaced for good measure as well. Both spares was taken from scrap boards.




Now I did expect to see some kind of change when replacing the broken 157, but not the kind that I saw when hooking the board up again...


Hmmm, must have done something wrong when fitting them sockets. Pulled the 157 again and had a look. Now I really appreciated myself for always using breakable header sockets instead of normal sockets, as this gave my a clear look down between the two rows. I found one of the tracks between a via and one of the pins suspicious, and the continuity tester confirmed my hunch.


Patched it up with a little piece of kynar on the solderside.


Now the boot error had gone, but there was still no change in regards to the graphics on screen.
Until now I had only concentrated on the primary PCB, so now I had a look at the secondary one. The component side looked incredibly fine, considering the damages found on the primary one. The solder side however had a fair among of scratches and was also pretty dirty.


I gave the worst place a light scrup with rubbing alcohol and tooth brush, and I found 1 pin touching a nearby via and a track that was scratched in 3 places. Again the continuity tester confirmed...


So straitened the pin (along with about 5 others that I found, for good measure) with a Stanley knife a alot of caution. Then patched the broken track with kynar.


And NOW, the intro screen


and the sprites where alive and kicking again };-)
(please take note of the cute up-skirt view you get in this pic };-P).


Now all was good, and I started test-playing the game. But when I tried a 2-player game, the hit-button for player-2 was unresponsive. A quick glance at the input section on the primary PCB, and my eyes caught this broken resistor array.


By measuring on one it's sisters, I found that this was not the same type as nomally used for pull-ups (with a common point). It was more like 4 parallel resistors just packed into one house. I couldn't find any of those on any of my scraps, so desided on just fitting 4 standard 220Ohms resistors. Now the original bootleggers had put 2 componentpins into each hole, but with the pin-diameter of the standard resistors, I had no chance of doing that. So I desoldered the standard pull-up array


and resoldered it so that it was possible to access the pins from the component side. Then I soldered the 4 standard resistors directly on the pins from the component side.


And once again our Red Hero is able to swing his pork chop against the baddies };-P


And finally this case is closed };-D

19
ARCADE / SNK Fighting Soccer Bootleg Repair Log
« on: November 15, 2011, 08:32:33 AM »
Now this board is a relatively new investment (from the same batch as M.I.A. http://elgensrepairs.blogspot.com/2011/11/konami-missing-in-action-mia-rep-log.html). A bootleg of SNK's Fighting Soccer. Before even connecting it, I could see that it have seen better days.

Here a broken cappy...


And had someone tried to drill holes in the PCB???


...not only two but THREE PLACES...WTF?!


Without getting my hopes up too high, I replaced the broken cap and hooked the poor thing up in the bench. Well first thing I noticed: No sound! But when I turned the volume pot on the board up, I did hear a hissing sound (It Still Alive };-)). Hmmm, a fast check with the voltmeter and it was obvious that this board didn't get -5V. Soon I found out why?! My JAMMA-extender didn't have -5V wired (note to self: Why do you keep buying premade stuff, that you could have done better yourself? Grrrr). Tried to hook up the board directly in the benches JAMMA-slot...



...and heard the well known SNK-boot-jingle from the speakers };-D
Wired the -5V on the extender and hooked the board up again.
A lot of the sprites had horizontal stripes through them.







By shortening adjacent pins on different RAMs and ROMs I quickly saw, that the graphics was (as with most boards with 2 PCBs) handled by the secondary PCB. So tested all data and address pins on the RAMs and ROMs with the scope, but found no oddyties.
Now, it way getting late and I felt a bit tired. I did however decide to do a little piggy-backing of TTLs before going to bed. The board have a cluster of 3 245's in the middle and I just happen to have a tube of them on the table, so I thougth: Let's give it a try:


 ...and to my big surprise, all sprites looked normal again. Quite a lucky punch (I so i thougth!).
I quickly desoldered the IC and put it in my Top2005+ for testing...hmm, the test came out successful??? The one I've used for piggy-back (the one from tube) also passed the test.
Fitted a socket and inserted the new one: Stripes through sprites!
Inserted the old one back into the socket: Stripes through sprites!!
Piggy-backed the new one on top of the old one: Still stripes through sprites!!!
(BTW: Did you notice that the words "sprites" and "stripes" have the exact same letters...kind'o'funny };-P).
Now I was really puzzled...Then tried piggy-backing the new on top of the 2nd 245 in the batch of 3: No stripes??? WTF!
I wanted to get to the bottom of this, so desoldered the 2 others as well and fitted sockets.



Slammed in 3 new ones from the tube: Stripes!
Put the old ones back: Stripes! (MOAN!)
I discovered that one of the 245's wasn't inserted fully into the socket. With the board still running I gave it a push, and the stripes went away?! Released the pressure and stripes came back. Began pressing on IC's in  the surrounding area: Same thing happend!!!



Picked up the board and bended it slightly with the same result.
Now we are getting somewhere; this smelled an awful lot like a short-circuit of some sort.
When looking closely at the joints on the solderside, there was alot of them looking very nasty:



This is just 2 examples, but this board has extremely many of them.
So started a shotgun-scheme, where I did a reflow on the nasty joints I could see checking the board every time. After about 10 of them with no luck, I decided to change strategy into a more systematic brute-force approach.
Started by cleaning the lower half of the board using rubbing alcohol and a toothbrush.



Then starting at ground-zero (the place where I had to apply the least pressure to provoke the fault), I began the process of reflowing the joints on every IC while working my way to the edges of the board. After having done an IC, I tested the board. And on the 18th IC I hit the jackpot!



It was this PROM who was the little troublemaker };-)


And now all the sprites looked good at all times };-D




Just before I close this log off, I'd like to share with you all this piece of beautiful hairdresser art };-P

20
ARCADE / Konami Missing In Action (M.I.A.) Repair Log
« on: November 01, 2011, 11:40:20 PM »
Now this board, an original Konami Missing in Action (M.I.A.), I snapped up cheap in a batch of 7 non-working boards paying about 100DKK (~$19~£12) each. Standard Konami GX-<something>; only one PCB and quite many custom ICs.



The problem with this baby was, that one (or maby more; a bit hard to tell) of the background layers and all the text had vertical stribes, where the graphics was just simply missing (in action, ha! ha! };-P).





Even in test mode it was same-same!



Now the board have had a rough time at some point; quite alot of scratches on the solderside.







But as the tracks and vias on the GX-boards are quite thin, it wasn't possible to test for continuity without desoldering some ICs in order to follow the tracks around on the component side. As I was a bit too tired for that, I gave the scratched tracks the benefit of the doubt, and started poking all the SRAMs with the scope. But everthing seemed quite healthy on both address and data lines.
I then started shortning adjecent pins on some of the TTLs near the SRAMs involved in the graphics rendering. That did stir the picture up a bit, but nothing that was so obvious, that it was worth investigating further.
Now had a closer look at the 4 PROMS in the top right corner of pic1. By removing them one at the time and trying to boot (and it actually did; that 'self-test' at start-up isn't worth a flying hoot on this boad };-P), it was obvious, that these contained the graphics for the game. Poking each data and address pin on them, I found that pin 18 (Q4) on the PROM labeled "808 E13"



was stuck low.



The corresponding pins on the 3 other members of that "PROM-family" was extremely active...so I decided to try and dump it with the Top2005+. But when trying to do so I got this:



Pulling and reinserting the IC a few times gave the same result.
This was quite art, as this was not pin 18, but something WAS clearly wrong with this mother frakker. Ahaaaa (his cried out loud!).
Now the PROM is an 27C512, so found a nice TexasInstruments TMS27C512 EPROM from a scrap board. Ripped the window sticker off and removed the remaining glue from the window with rubbing alcohol and an old tooth brush. I was quite eager, as I had never had a chance to use the Top2005+ to actually program an EPROM before.
So into the eraser for 3mins it went



Checked it in the Top, and as it was now filled with all nice 1's, 3mins seemed to be enough. Now downloaded the MAME ROM and programmed the right image to the newly erased EPROM.



Verified the IC, slammed into the socket aaaaaaand:





TADAAAAAA!!!!! };-P
Now wrote a nice little label to put on the window of the EPROM, and the board is as good as new.


21
ARCADE / Legendary Wings Bootleg Repair Log
« on: October 28, 2011, 07:31:34 AM »
I have had this bootleg of Capcoms Legendary Wings on the table a couple of times, but that was before I owned a programmer, desoldering station, and a scope, so I had to give it up. But now I decided to give it a final try before scrapping it.

The problem was, that all sprites had blue stripes running through them in the direction of the scanlines and the game had no sound.



The board is far from prestine; it has a lot of scratches etc. Some broken tracks on the 2nd board was obvious with just the naked eye.



This pic is taken with a halogene lamp behind the board.



And for the sound it was pretty obvious what was wrong too.



I thought this would be easy. Started off by trying to repair the 2 broken tracks on the pic, but the tracks went under an IC, and I was not able to see where they went. And as they where broken I couldn't just beep at random to find the end points.
Very bold I fired up my brand new Aoyue 474+ desoldering station (a quite good one for the hobbyist I might add) and tried to remove the IC, but I was too impatient and broke it in the process };-( I don't think that I have the 'wiggle' quite right yet...
Well I then found that the track continued under another IC, so fitted a socket and desoldered that too, this time with greater success };-)
I now had the 2 end points and was able to patch it with kynar on the solder side and smack in a placement for the broken IC.
To my surprise it didn't change a f... thing!

Started shortening adjecent pins on RAMs on the 2nd board, as this usually handles graphics and soon found 2 pieces of HM6148P (4bit wide general purpose RAM some times used for sprites). When shortening some of the data pins on them, the sprites (and also the blue stripes) started acting up.
Decided to desolder both (broke one of them) and test them in the Top2005+. But when trying to find the 6148 in the list of surported SRAMs to test, I couldn't find it. Googled for cross references; they where not there either...  };-( the FRAKING thing can only test SRAM that are 8bits wide, WHY!!!



Fitted 2 sockets and reinserted the one chip along with one from a scrap board.
Well now I had a section of the board looking like this.



Now poked the data lines of the 2 SRAMs with the scope and found 1 of them stuck high. As I couldn't test the SRAM, I had to assume that it was ok and went looking for what else was on the databus line. Now I was glad that I had socketed some of the ICs, as the track went under some of them. Well first I found the input of a 273 flip-flop; properly here, that the signal is transmitted to the later parts of the graphics system. Then a pull-up resistor array (ahhh, so that's why it's stuck high...it might not be driven at all). It ended at the output of a 257 multiplexer. One of the inputs for that was stuck high (again pull-up resistor), and when closely inspecting the track that went from there to a via using a multimeter, I found it broken. I couldn't see it with the naked eye. Patched it up, and....



...all sprites back to normal };-D
Ended up with a solderside looking like this



I have a strong feeling, that none of the ICs were bad on this board, I was just unfortunate to break 2 of them during desoldering.

Now the sound pot was fixed in a matter of minutes



and finally I could play a test game.

The board do infact still have a small issue; the text when coined up is kind of 'transparent', but as it has no influence on game play, I choose to don't bother for now.


22
ARCADE / Cross references for 4, 8 and 16 bit SRAM ICs?
« on: October 20, 2011, 03:02:47 PM »
Does anybody have a link, a good book, txt-file or anything for good cross references for SRAM (4, 8, and 16 bits)?
TTLs are easy, as there is a standard numbering system, but for SRAMs it's a bit of a jungle to know heads from tails (can you even say that in english, or is it just poor translation of a Danish expression?) of all the different brands...

23
ARCADE / Can Cabal trackball-version be converted to joystick-version?
« on: September 28, 2011, 07:57:27 AM »
I managed to snap up an original Cabal (TAD-8710 board). Got it cheap, as seller claimed it to be defect (no sprites). But only thing wrong was that the ribbons were fallen out of their sockets; easiest fix ever };-P

Now 'problem' is, that it's the trackball-version, and I don't own any trackballs. Question now is: Can it be converted to joystick-version?

Initially I didn't think so, but then found this on klov:

...When converting from track ball version, please change IC D4701AC (2pcs)
at location C D 1 2, on bottom board with socket plug in adaptor....


http://www.arcade-museum.com/pinouts-game/7252.html

When I look at my board it actually contains 2 D4701AC at positions C D 1 2.

So now it comes:
1) Anyone knows anything about this socket plug in adaptor?
2) Anyone have one?
3) Anyone have a diagram so I might build one myself?

24
ARCADE / Turbo Force Repair Log
« on: April 25, 2011, 10:36:38 PM »
Now I did do a mock-up of this somewhat easy repair with just some hook-up wires a few months ago, but always had a feeling that it could be done nicer. And now it just bugged me so much, that I had to do it...and why not make a log for others to see, I thought };-D

Got this original Turbo Force as untested in a larger batch of untested boards.


It wouldn't do anything just black screen and no sound.
This construction immediately caught my eye; the sub board had a loose wire hanging from it.

And when I pulled the sub board from it's socket, I saw that the thin bit were broken off of 2 of the pins

and one of the pieces were still stuck i the socket.

I managed to remove that with 2 needles and alot of patience.

Now my first plan was to saw a bit of the 2 broken pins and pacthing them with 2 pins of header strip by soldering them on.


But I must have been too eager when sawing and wiggled the pins too much, cause they broke off at the end soldered to the sub board, also taking the pin beside them in the fall with them };-(
So that plan was out. I then remembered that I had a strip of these from a batch of scraped components I got from a shop once


I straitened 3 of them out and pulled them out of the socket. Cleaned the holes on the sub board, soldered them in, and cut them down to the right lenght.


Now I had to deal with the loose wire. Putting the sub board back in place, the lenght of the wire gave my an obvious radius on the board to investigate. I quickly found a pin on a socketed IC with a blob of solder on it


Tried connecting the board just pressing the wire against this pin, and viola:


Now I soldered the wire on


Case closed.

Actually it's a great vert shmup only using 1 button; smart bombs can be picked up, but are fired immediately upon pick up. The board also have a molex for a 3th controller so you could play 3 players simultaneously; I'd like to have a try at that some day };-P

25
ARCADE / Ginga Ninkyouden Bootleg Repair Log
« on: April 20, 2011, 12:37:11 AM »
I got this stack of 8-9 "untested" boards cheap about 2 years ago.
The defects (4 of them, it was) have just been stashed away in a box ever since my first test of them.
One of them was a bootleg Ginga Ninkyouden; a pretty frakked up beat'em'up by Jaleco.

A main and a secondary board connected with ribbons.

The backgrounds, text, sounds, controls and gameplay was good, but all the sprites were messed up.
It looked like the sprite-parts displayed fine, but in the wrong place.

Easy to see here in attract mode, where we have a line-up of most of the baddies starring in the game.


Also right upon start-up the message "RAM ERROR" was displayed very shortly (not easy to catch).


Okay, so started with the RAMs on the secondary board, as this is usually this one that handles graphics.
Started by shortening adjacent address and data pins on the different RAMs observing the screen.
That way I found RAMs used for colour, backgrounds, and texts, but no sprites.
Well it turned out, that the sprite RAMs were on the main board after all.

After having read GameDudes repair log on G'n'G over at Aussie (http://www.aussiearcade.com.au/showthread.php/20920-Ghost-n-Goblins) that also had misplaced sprites, I started poking the 273s on the main board.
Soon I found, that the one at V7 had both pin 12 and 13 stuck at high, while all the other in- and output were very active when there was sprites on screen.


As both in- and output were stuck, I began to trace what was happening upstream and found the output of a 244 at N8, aaaand BINGO! Found rot around the corresponding input pin.

(At this point, my hands were shakey and my palms moist, had I found my first REAL arcade hardware bug?)

By beeping, I found, that all the remaining inputs were tied to a an in-/output on the 245 just next to it at M8.
Only one was not (the plot thickens, MUAHAHAHA!). Tried to connect the two pins by just poking a piece of wire at both, and viola: All sprites back to normal!


Fired up the soldering iron and made a hook-up on the solderside, as this side is inside the sandwich when the two boards are combined with legs.


Now the game works perfectly. I still get the "RAM ERROR" message at start-up tho, but as the game seems to be working, I don't quite know what to make of that?!

I consider this case closed...my first REAL arcade repair };-P

26
ARCADE / Crazy idea for a hack...
« on: April 08, 2011, 07:45:49 AM »
Okay I've always been accused of getting really crazy ideas, and now I want to hear your opinion on this one.

I got my Top2005+ EPROM Programmer yesterday. It works fine and I love it. BUT it 'only' programmes EPROMs that are 8bit wide on the databus.
I think it could be cool to be able to programme say a 27c1024 (as it's used for ie. the MVS-bios).

To do that I would:

1) Start by finding an 8bit IC covering the same address space as the 27c1024 that my programmer know of; that would be 27c512.
2) I then take the file I want to programme and cut it in half, by taking all the lower 8 bits of the 16 bit bites i one file and all the higher in another. It should be fairly easy to find a hex editor that can do that; alternatively I could just write a little piece of code for it };-D
3) I now make an adapter for the programmer:
  a) All address lines from the 27c512 just goes to the corresponding lines on the 27c1024.
  b) For the datalines I make a switch; in position 1 the upper 8 bits are held high and the lower is connected to the data pins of the 27c512, in position 2 the lower 8 bits are high and the upper connected to the data lines (for this I will need a bit of TTL logic, but it doesn't sound too complex I think).
4) I then first programme the lower 8 bits for whole the address space, then flip the switch and programme the upper 8 bits.

My question is this: Do you think that'll work?

It all matter of if it's possible to reprogramme an IC that have already been programmed before WITHOUT an erasing step.
My theory is, that by pulling the bits not being programmed up, they will stay untouched by the programming step, also in the 2nd iteration.

But what do you all think; I'm I way off or what? };-P

27
ARCADE / Good place in EU to buy lots og ICs, EPROMs, and sockets?
« on: March 30, 2011, 04:38:20 PM »
I have over time collected myself a fairly good stock of different analog basic components, but lacks a good basic stock of ICs (the most common TTLs and CMOS og EPROMs) and sockets most commonly found on arcade boards.

Anyone know of good places (online shop) in EU? Where do you buy your stuff?

28
ARCADE / Defective (original Irem) R-Type
« on: March 24, 2011, 08:04:42 AM »
Hi

I'm new here on the board.
My name is Elgen (aka Morten irl };-D), and I've been messing with arcade for about 5 years now.
I've done only very simple repairs like changing a capasitor or resistor, patching a broken circuit or IC-leg ect.
I have to say, that when I found this board, I was impressed; it's a gold mine of repair logs, truely inspiring };-P

Well now for the issue:
I have an R-Type (original Irem).
All the sprites display well, the controlls, gameplay, and sound is also good.
But the backgounds is all messed up. There are big rectangular patches of striped and solid goo, and there is white vetical stripes on the whole screen.
See video here: http://www.youtube.com/watch?v=If9BXlpWDz0
I'm suspecting this could be a RAM issue, but I don't know much of these things (yet?!).

Well bottom line, I've desided, that I want to give it a try at repairing it, but where do I start?
I've been through the standard things:
- Checking for physical damage.
- Taken the 3 boards apart cleaned all connectors putting it back together.
- Had all socketed IC up, cleaned legs and sockets and reinserted them.
Still the same. As said before I've never done REAL repairs of arcade, but I've got the tools (scope, multimeter, soldering iron etc.), I'm real handy, and I'm a fast learner when it comes to technical stuff (bordering autistic };-D).

Do any of you have any clue as to where I should start with this one?

I will ofcause post all progress here on the board };-D

Hope some of you will be willing to help a repair-n00b out.

PS. I've build my SuperGun/TestRig myself; you can see how that went by here (all comments in Danish, sorry): http://www.facebook.com/album.php?aid=110508&id=1390686556&l=d171261ea5

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