738 ULA's

Reverse engineering is mostly a matter of re-constructing the function of a component - and then replace that function with other component(s). Sometimes requiring very high-tech, expensive test equipment. Or not (like in this case). Depending on what's being reverse engineered, not necessarily difficult. But often very, very time-consuming.

I suspect that given the number of SVI-738 machines & users, it's just not worth the effort. Less so as number of machines & users declines. And thus nobody bothered so far.

If you mean IC52 "ULA9RA041" in schematic: agreed, looks like it.

If you mean IC35 "ULA5RA087" in schematic: yes, probably.

...will be hard to find. Either you'd have to figure this out yourself, or find some other way to fix the problem.

Btw "as they seem to cause problems..": have you investigated this closer / excluded other causes? Electrolytic capacitors that have gone bad? Tested with an external power supply? Bad contacts in IC sockets? Cracks in circuit board traces? Swapped IC's with another SVI-738? Tested IC's in other computer with same IC inside? Asking because this kind of IC is generally quite reliable.

yes sorry have a skope and probe comming to check..

I noticed that in my Yamaha the relay clicks in case of some bad event, for example if some data/address lines are shorted to the ground for whatever reason. Check the cartridge slots and the entire board for possible shorts. And yes, RAM could be the main suspect. I would recommend to use a RAM expansion cartridge first and some simple game cartridge. If the machine boots with them, then the problem is surely in main RAM. However please check if some data or address lines are shorted to the ground with a multimeter.

ok some more info.. i tried a cart i found and ti's still no go i even replaced the 64kb ram.. i did notice that when i had the cart in and powered on the caps led went out but still nothing..

will get chance this week to try the scope.