Defender.
- Thread starter Lurch666
- Start date
Not normal, here's the reference https://www.robotron-2084.co.uk/williams/tech/cpu-decoder-prom
For info, decoder 1 and 2 are identical
For info, decoder 1 and 2 are identical
Actually I have just noticed that there's a H on one prom and a V on the other. Will try switching them around and see if anything changes. At the moment I'm getting the rug twice then a blank screen. LEDs 2 and 4 are then lit. If I leave it it sits for around 30 seconds then resets or I get some text at the bottom of the screen about how to advance or test which I think is part of the bookkeeping menu.
Swapped the decoder roms and the rug pattern didn't appear properly so they are different unless one or both are failing in different ways but for now I'll concentrate on getting it running properly since these roms appear to be for graphics and so I'm assuming they wouldn't stop the game from running.
I've replaced most of the sockets on the rom board and am waiting for a replacement PIA chip.
I wired up some controls to see if the text would change but it looks like it's locked and since the text quality improved when pressing on certain ram chips it looks like I'm going to have to replace all the ram sockets as well.
I've replaced most of the sockets on the rom board and am waiting for a replacement PIA chip.
I wired up some controls to see if the text would change but it looks like it's locked and since the text quality improved when pressing on certain ram chips it looks like I'm going to have to replace all the ram sockets as well.
PIA replacement turned up today but it's made no change.
I decided to see if I could read the decoder proms in my old pinmaster48 but no go.
Then I looked to see if my slice would read the 7641 proms and it does.
The one marked H matches the decoder.2 file in mame as far as it was being read but the one marked V had errors on certain values when checked against the decoder.3 file and I noticed pin 4 (A4) was showing very little activity. On checking I found no continuity between pin 4 of the prom and pin 14 of 5E that generates the address signals. Turns out it was down to the socket.
I was thinking of replacing them anyway but now with a patch wire it now boots to the message 'initial tests show ram error' so at least I can now see what's going on.
Onto sorting the ram out next. I'll see what spare ram I have and decide if I want to mod this board to take 4164 ram.
I decided to see if I could read the decoder proms in my old pinmaster48 but no go.
Then I looked to see if my slice would read the 7641 proms and it does.
The one marked H matches the decoder.2 file in mame as far as it was being read but the one marked V had errors on certain values when checked against the decoder.3 file and I noticed pin 4 (A4) was showing very little activity. On checking I found no continuity between pin 4 of the prom and pin 14 of 5E that generates the address signals. Turns out it was down to the socket.
I was thinking of replacing them anyway but now with a patch wire it now boots to the message 'initial tests show ram error' so at least I can now see what's going on.
Onto sorting the ram out next. I'll see what spare ram I have and decide if I want to mod this board to take 4164 ram.
After much messing around I've got the 'initial tests indicate unit ok'.
Then I get a blank screen.
I put batteries in the board to stop the bookkeeping screen from coming up but for some reason the game just won't boot into the demo mode.
Then I get a blank screen.
I put batteries in the board to stop the bookkeeping screen from coming up but for some reason the game just won't boot into the demo mode.
Check the count240 circuit
So count240 appears to be ok. It's reaching the PIA as well. It's got a tiny propagation error shown by slice but not enough to stop everything working.
@philmurr :
I have been using the term 'williams defender' when searching for help because just 'defender' brings up jeeps so I missed your comments in the KLOV thread talking about this issue.
I have also checked the LS32 at 5P and it seemed off so I changed that one but no difference.
It's not exactly a blank screen I'm getting after the 'unit OK' message:
There are two dots on the left of the screen. The top one is flashing.
I've tried the video probe but as far as I can tell no proper graphics are being produced.
@philmurr :
I have been using the term 'williams defender' when searching for help because just 'defender' brings up jeeps so I missed your comments in the KLOV thread talking about this issue.
I have also checked the LS32 at 5P and it seemed off so I changed that one but no difference.
It's not exactly a blank screen I'm getting after the 'unit OK' message:
There are two dots on the left of the screen. The top one is flashing.
I've tried the video probe but as far as I can tell no proper graphics are being produced.
Now I'm reading through the theory of operation. Checking through O1-O4 I think I should see some graphics with my video probe since they turn the parallel graphic data into serial data but I'm seeing nothing that looks like defender. I would think it's an issue with the graphic roms but all roms pass the startup check.
It's also annoying how it can display the text in startup and the bookkeeping menu but nothing in game.
Got a few things to check that relate to this area so hopefully I can find something.
It's also annoying how it can display the text in startup and the bookkeeping menu but nothing in game.
Got a few things to check that relate to this area so hopefully I can find something.
There are no graphics ROMs, the video ROMs are there to allow the CPU to more easily access the video RAM, graphics are all bitmapped from the RAMs
Once you get to the hung screen can you press the reset button, the game should go through the rug pattern and again you should get "unit ok" again, then post what happens next (it may be just the same)
Have you checked the other bits I mentioned in that KLOV post (CMOS RAM, vertical position count)?
Once you get to the hung screen can you press the reset button, the game should go through the rug pattern and again you should get "unit ok" again, then post what happens next (it may be just the same)
Have you checked the other bits I mentioned in that KLOV post (CMOS RAM, vertical position count)?
A reset produced identical results.
CMOS ram was checked when I was getting rom/ram fail and that passed. I just tried known good in the socket and that made no difference except for causing the bookkeeping to appear again.
The vertical position count comes from the LS32 at 5P doesn't it? I swapped it out but it made no difference.
CMOS ram was checked when I was getting rom/ram fail and that passed. I just tried known good in the socket and that made no difference except for causing the bookkeeping to appear again.
The vertical position count comes from the LS32 at 5P doesn't it? I swapped it out but it made no difference.
Dammit. I followed the line on the schematic wrong. I thought it fed into 5E.
Just sliced it and 3D is working fine.
Did also just find out I got a bad output on pin 9 of the LS74 at 5S.
Early shift now so got to hit the sack but will have a closer look tomorrow at 5S.
Just sliced it and 3D is working fine.
Did also just find out I got a bad output on pin 9 of the LS74 at 5S.
Early shift now so got to hit the sack but will have a closer look tomorrow at 5S.
5S changed.
No difference.
I thought I would try and connect the speakers to see if the game was actually running. Found out that the sound board isn't working.
The reset is missing on the sound board but even if I manually bring the reset pin high it's not making any sound. Will fix that later after I get the main board showing something.
No difference.
I thought I would try and connect the speakers to see if the game was actually running. Found out that the sound board isn't working.
The reset is missing on the sound board but even if I manually bring the reset pin high it's not making any sound. Will fix that later after I get the main board showing something.
This damn thing just isn't giving up it's secrets to me.
Double checked 3D and 5P with my scope,replaced the ribbon cable between the rom and cpu board and checked the inputs and outputs of the graphics ram and the various associated chips but nothing is showing me what's wrong.
Double checked 3D and 5P with my scope,replaced the ribbon cable between the rom and cpu board and checked the inputs and outputs of the graphics ram and the various associated chips but nothing is showing me what's wrong.
Does SCREEN CONTROL stay low under normal operation?
I've replaced all the rom sockets and checked all the roms except 2 and 3 since that meant digging out my old pinmaster again.
I had assumed they were good since it passes the rom check but now I'll double check them all.
No spare rom board.
I've replaced all the rom sockets and checked all the roms except 2 and 3 since that meant digging out my old pinmaster again.
I had assumed they were good since it passes the rom check but now I'll double check them all.
No spare rom board.
Almost forgot.
Thanks @philmurr for helping me get this far.
I cleaned the legs of the sound rom and tried raising the reset pin high again and saw activity on the rom. Tried the test button and got a repeating sound so I really need to sort the reset circuit.
I'll try changing the caps first and if that doesn't work the resistors will be checked next followed by replacing the transistors.
Thanks @philmurr for helping me get this far.
I cleaned the legs of the sound rom and tried raising the reset pin high again and saw activity on the rom. Tried the test button and got a repeating sound so I really need to sort the reset circuit.
I'll try changing the caps first and if that doesn't work the resistors will be checked next followed by replacing the transistors.