Defender sync.

[cliff_poole]

Andyman has just received a late revision Defender CPU PCB that I sent him but it seems to have sync problems in his Williams cabs, three monitors that otherwise work OK. I'll admit that I don't have a real Williams monitor to test it on.

My test rig consists of a JAMMA loom with a 7486 circuit to combine and invert the H and V sync outputs (so that I can test the older boards), so I was using the H and V signals to test and it was fine on my monitor. Andy's monitors also use seperate H and V, but at first it would not sync at all. The PCB had not had the sync inversion track cut, so he has cut this which has stabilised the picture somewhat, although now the picture wobbles in the horizontal.

Does anyone have any ideas what might cause this ?.

Looking at the schematics, I can see that the sync mod inverts the H and V as well as the composite, I'm wondering if we have done the right thing.

Thanks,

Cliff.

 

[tb lilley]

Hmmmm .... Shouldn't really need to force Defender board to output negative sync in order to get monitor working correctly. That said, whether negative or positive, if connected up correctly then should work.

This useful link covers most combinations and may be of help.

 

[andyman]

Defender is natively + sync. which is output on pins 5&6 of the video connector. On the later series + composite sync is output on pin 7 but the track needs cutting to use it. Cliff you had cut the track so you could jammatise it, I bridged it back so I now have + H & V seperate sync which the WG's like.

- sync is used by 90% of the other games.

 

[tb lilley]

I thought pin 7 was + composite sync. Cutting the track makes it negative (Jamma friendly)? Anyway, must be pleased to have Defender back in action.

 

[andyman]

Nah, cutting the track enables it, you have to use an inverter 7486 to make it - sync

Still not working properly, looks like I'm off to trace sync signals

 

[cliff_poole]

Sorry about that. Let me know if you want to send it back, I'll refund postage too.

 

[chadsarcade]

Are you sure the on-board 7486 is working and inverting the signal (or not)? Cliff said he used an external 7486 on his test rig.

G07's and some WGs have a separate 3-pin connector near the video input connector for inverted sync - it may be worth trying to connect the syncs to that and see what you get, if your monitor has that connector.

 

[andyman]

Ok weird one, it is running + sync still but somehow H & V have become reversed. Original wiring loom never touched, I swapped H & V and it works

Although other board with ram error, sync is now messed up

 

[cliff_poole]

That is weird !. It makes sense, combining the two signals with an XOR gate I wouldn't have noticed. I'll know to check on the scope next time. I wonder if it is some strange revision of board ?.

 

[Judder]

I have a later revision Williams CPU motherboard, configured to run Joust which has the sync all over the shop - you can see the picture but it scrolls/slices (*haven't tried reversing it but will do) and as my Defender cabinet is, well, a Defender cabinet, there is no wire to use the composite sync.

Using a working Stargate board set, the sync. is all fine so perhaps some of the later boards do have H & V around the other way??

[Hi Andy - can't believe your having problems with yours after fixing mine

]

 

[andyman]

Haha I was fixing yours when I stepped back and stood on my CPU, then it stopped working

 

[andyman]

And after leaving on for 3 hours to make sure all was ok, the monitor decided to eject magic smoke and die

Anyone have any idea where I would get a 6100pf 1500V polyprop capacitor from that isn't in the US !!!