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
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
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.
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.
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