Solved Robocop bootleg conversion help

[Jacmar]

Hey guys,

I've been messing around the last few days with a DragonNinja bootleg (I've had for ages but don't play) trying to convert it to Robocop ..
I'm close to completion but have an issue where the screen freezes (code continues to run) during the attract mode on the animation of the gun drawing from his leg ... I believe on the Robocop bootleg graphics pcb, there is a TTL chip with a leg cut, which (when cut) should solve the freezing issue. But I cant find any decent resolution pictures online and I don't have a Robocop Bootleg myself. So I'm asking if anyone who does have one, and could spare the time, to take a few decent pictures for me of the graphics pcb, particularly of any IC's with legs cut !?
🙏thanks

 

[Lurch666]

I have one. Busy tonight but if no one has sorted you out by tomorrow I'll dig it out.

 

[Jacmar]

Amazing thanks mate! if anyone else wants to chime in first and save Lurch the job, go for it !
In fact please do so anyway, there could be a few different versions of the circuitry of Robocop bootleg (there is for DragonNinja)
so the more pics the better !!!

 

[Flyback2021]

I have one also but won’t be tonight . Can try tomorrow afternoon tho

 

[Jacmar]

Great stuff thanks. No rush just whenever you have the time free !!
Much appreciated !!!

 

[Lurch666]

The LS138 pin 13 might be the one you are looking for.

 

[Jacmar]

Cool, I'll give that a try , thanks a lot
Don't suppose there's any chance you could do a picture of that full pcb please ?

 

[Lurch666]

 

[Jacmar]

Thanks again
I tried cutting that LS138 pin but it just ruined one of the background layers .... hmmm
I see a few differences to my board set ... more investigation needed !!!

 

[Lurch666]

On closer inspection the pad that leg 13 was attached to is now connected to pin 14.

 

[Jacmar]

Ah ok I'll try that out..

could I be a pain and ask another favour ..if you get time, could you continuity check a couple of signals for me please
Specifically the 2x 27C512 character roms that look to be labelled A22 and A23 on your board
I'm particularly interested in both their Pin 1's (A15) and Pin 27's (A14) and what they are connected to ... each other, toggling signal (if so from where), tied to gnd or +5v
Thanks!

 

[Lurch666]

The pins on both chips are connected together pin 1 to pin 1 and pin 27 to 27. There's a patch wire joining the pins 1 together. A trace goes from the pin 1s to pin 9 of an unpopulated LS157 (the one with the cap between pins 8 & 9) and pins 9 &10 are connected on both missing 157 places as are pin 12 &13 with a 471 cap between pins 9 and 8 (GND).
Constant activity on pin 1.

Pin 27 has a trace that goes to pins 12 & 13 of the same missing 157 with the cap.
Brief activity on pin 27 during intro with a bigger spike when robocop draws his gun (where yours crashes) with constant small spikes during demo gameplay.

 

[Jacmar]

Amazing thanks man !!!

Does one of those ROM's (probably A23) pin 1 have a cut trace to +5v by any chance? (and then tied to the other pin 1 with the patch wire) ?

 

[Lurch666]

As far as I can tell it looks like the pin1 of A23 was not connected to anything and pin 1 of A22 has a factory trace going to the missing LS157.

 

[Jacmar]

No worries, that all makes sense and confirms the correct signals for the larger 512 Character Roms Robocop uses

 

[pedro72]

View attachment 62456

The LS138 pin 13 might be the one you are looking for.

We’re can I get one of these from

 

[Lurch666]

What? An LS138 or a bootleg robocop/bad dudes?

 

[Jacmar]

That's what I was thinking too

 

[Jacmar]

I've cracked this now, thanks for your help @Lurch666