Not Pinball, But Super just the same

[deep six]

Hi All

Out of my 4 machines I recently acquired, the Sega Super Hang on is about the closest to running order I have, was working on the galaga a,little while back but switching over to this one for now.
Problem is the screen has horizontal colour bars running across and makes it hard to follow the game.
Following suggestions from strangeways "Sega with horizontal bars - reseat the edge connector. Check the +5 Volts. Reseat the eproms."

I have disconnected and re-connected the edge connector, didn't seem to make much difference
Check the +5 volts..... not quite sure where to check this at???, I have a multimenter but a little apprehensive about shoving my hand inside a live machine.
Re-seat the eproms..... I can see the main board with the side cover open but not quite sure what the eproms look like,

The game does run, reset works, coin mech works, the screen clarity seems to be improving a little with time but definetely would like to loose the horizontal bars.
Here is a shot of what the screen looks like.
Cheers and thanks in advance

[dj10555]

On the main pcb, the eproms will be in sockets and normally have a sticker on them. All chips (Eproms and others) in sockets can be re-seated to see if this will fix the problem. To do this gently slide a flat blade screwdriver between the eprom and the socket and lift it up slightly.  Don't worry about pulling the chips right out, just lever them up 2-3mm and then push them back down. When you are levering the chips, make sure you keep the screwdriver blade parallel to the board otherwise you may damage the tracks located under the sockets.

The best place to measure the 5v is across a couple of the chips on the main pcb. If you can post a picture of the board, we might be able to suggest a suitable location.

regards Derek

[deep six]

Hi Derek

Many thanks for the tips mate, will give the eproms a lift and see what they say, I'm a little worried about doing some damage with the screwdriver but I think I have a puller thingy in my pc tool kit from way back.
Here is a pic of the main board.

[ajlaird]

Honestly, in my experience two small screwdrivers used judiciously a little at a time on both ends of the EPROM is better than a chip puller.

[Strangeways]

As described, a flat screwdriver will do the trick. Simply insert the screwdriver between the eprom (with the white stickers) and the socket and gently turn the screwdriver. Then do exactly the same thing to the other side of the eprom. This will lift the eprom. Then simply push it back into the socket. You don't need to lift the eprom too high.

Looking at the image, it does look like an Eprom issue as the background graphics are not correct.

[deep six]

Thanks guys, here is what I did, since I have my Galaga machine on a bench in my garage, and the main board is easy to remove, I figured I would practice on this one first.
It has a similar issue with screen problems so I figured if I could fix this one simply I would be miles in front, and if I buggered it, well its probably an easier fix than the Sega.
I rummaged through my tool box and found a small screwdriver that was fairly blunt and went to work on the galaga board.

Firstly I wanted to completely remove an eprom to make sure I wasn't doing damage to the tracks underneath, turns out the eprom sits pretty high so unless you go mad and jam the screwdriver right in you are pretty safe.

Carefully replaced the first eprom and went around and slightly lifted and reseated the rest of them.
They gave a satisfying creak sound as they re-seated so sounded like it was all good.

Put the board back in, plugged her in and waited expectantly while the old tube warmed up but alas, still the same as before.
Oh, well, maybe i didn't re-seat them enough I thought so pulled the board back out, lifted them again and went back to eprom number one ( the one I had pulled out completely). Once I pulled it back out I noted to my horror I had bent one of the legs when I put it back in the first time.

I carefully straightened out the bent leg, and extra carefully pushed it back into its socket.
OK, now it ought to work, plugged it back in, wait for screen to warm up, but same as before.

Not sure what is up with the galaga, could be something is burnt out on that board. I did note when I put a multimeter to the +5v supply (at the power supply) that I was getting 5.4 volts and at times up to 5.6volts, not sure if the power supply is supposed to run at dead on 5volts all the time so maybe this is part of my problem.
Here is a pic of what the screen looks like.

Cheers

[Strangeways]

5.6V is too high. I'm not sure if it is the problem, but you should be able to lower the voltage on the power supply with a plastic screwdriver. The power supply will have a small hole with the 5V trimpot behind it. Most likely on the same side as the terminals . Most boards are happy at 4.8 - 5.2 Volts. You could try lowing the voltage.

Do you know if it is a Jamma board or an original Galaga board ?

[deep six]

Hi SW

Thanks mate, I now see the adjust screw on the power supply, I don't have a plastic screwdriver, you mean plastic tip right??
I can unplug the power, unplug the board, give the screw a half turn and power it back up and check with the multi meter, would that work OK.
Not sure what sort of board it is, looks pretty old, the cabinet doesn't seen to match any dedicated galalga cabinet I've seen so perhaps is a generic cabinet that could accomodate different games.
As for Jamma, I've been doing a little research, so far have found what Jamma stands for but not sure what my board is, there is an ugly looking adaptor that plumbs the board into the cabinet loom but not sure what that means.
The board does have Galaga written on it in permanent marker but don't know much more about it.
Here is a pic of the board.

[Strangeways]

Platic tip screwdriver will be fine. But you make the adjustment while the game is on, with the multimeter on the +5 and GND points on the power supply. Turn anticlockwise - slowly - and observe the voltage drop on the multimeter. Try to get it as close to 5V as possible.

That's a strange board. Looks like some sort of conversion.

[Boots]

Hi SW

Thanks mate, I now see the adjust screw on the power supply, I don't have a plastic screwdriver, you mean plastic tip right??
I can unplug the power, unplug the board, give the screw a half turn and power it back up and check with the multi meter, would that work OK.
Not sure what sort of board it is, looks pretty old, the cabinet doesn't seen to match any dedicated galalga cabinet I've seen so perhaps is a generic cabinet that could accomodate different games.
As for Jamma, I've been doing a little research, so far have found what Jamma stands for but not sure what my board is, there is an ugly looking adaptor that plumbs the board into the cabinet loom but not sure what that means.
The board does have Galaga written on it in permanent marker but don't know much more about it.

The best way to find out is to start checking the pins on the connector with your multimeter.
With the machine OFF and the connector removed from the board, check the wires one by one and match what you get to a JAMMA pinout diagram.
Start with the 5V and 12V power and  it won't take you long before you can see if its wired to JAMMA or not.
There are some 28/56 pin variants out there that are nothing like the JAMMA pinout so it will be pretty obvious.

Give the contacts on the board where the connector goes a good clean with a regular white eraser, then have another look at the connector pins, if they are not shiney, it may pay to change over the harness or connector.
You can get all sorts of wierd stuff happening when you have dodgy connections, even check any other connectors the machine might have.

With the ready made JAMMA connectors around today it almost doesn't pay to get out a soldering iron.

[deep six]

Hi Guys
Didn't have a plastic screwdriver but I turned everything off, backed off the voltage screw, which only turned about an 1/8th of a turn anyway before it was seated.
Fired the machine back up and I now have 5.09 volts at the +5v terminal.
Good enough I figure, still doesn't run properly though.
Did a bit more research on Jamma, I suspect the board is Jamma 'cos it has a 28pin connector, the  cabinet has an 18 pin connector and there is an adaptor loom fitted in between to hook the two together.
I'm really not getting too far with this machine, I think I will sit back and think about it, but I am progressing.
From other research it seems as though a possible cause is poor contact between the eproms, already addresses but perhaps need to pull all the eproms and clean the legs, a delicate operation so still pondering on that one.
Anyway, thanks so far for all the excellent input.
Cheers

[Boots]

Did a bit more research on Jamma, I suspect the board is Jamma 'cos it has a 28pin connector, the  cabinet has an 18 pin connector and there is an adaptor loom fitted in between to hook the two together.

Don't assume its JAMMA just because its a 28 pin connector, there are other 28 pin configurations.