Bombjack ram location
- Thread starter Retroman839
- Start date
Retroman839
Senior Member
Prob turn out to be 1 or 2 broken traces and I will find em. Could be this evening ☺️
Retroman839
Senior Member
I wanted to find a bad trace or 2
But no joy !
All traces are fine,
But no joy !
All traces are fine,
Retroman839
Senior Member
Scoping pin 7 of the 148 @ 3m
Pin 7 active if games active ,
at insert coin screen pin 7 inactive .
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Retroman839
Senior Member
Yeh this 157 @ 5n is
Giving strange results
More of a puls than a square wave
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GadgetFreak
Active member
It's going to vary with the data!
You seem to be jumping around with your tests. Slice one moment then scope the next. You need to have a more methodical approach or you will just keep going back over the same stuff.
One thing is to make a Project in Slice, then you can capture results you get. Handy to look back over when tracing schematics and looking for signals.
The thing to note is that your basic gfx seem to be fine, it's just that their colours are completely screwed.
For instance the test screen, all the colour blocks are Blue, means no red or green is being enabled and blue is being enabled when it shouldn't. Also the background should be black but ends up being white which is all colours at max.
I think a possible fault is that the Palette ram at $9c00-$9cff is not being written correctly. A good place to start checking this is to look for the select signal that comes from the 74LS139 @2S pin 10 on the bottom board.
This goes into 74LS138 @ 8D pin 5 on the top board and generates the read / write signals for the palette ram.
The 74LS08 also has 2 gates used with these select signals, pins 8-13, these control the data buffers enable and direction control.
You seem to be jumping around with your tests. Slice one moment then scope the next. You need to have a more methodical approach or you will just keep going back over the same stuff.
One thing is to make a Project in Slice, then you can capture results you get. Handy to look back over when tracing schematics and looking for signals.
The thing to note is that your basic gfx seem to be fine, it's just that their colours are completely screwed.
For instance the test screen, all the colour blocks are Blue, means no red or green is being enabled and blue is being enabled when it shouldn't. Also the background should be black but ends up being white which is all colours at max.
I think a possible fault is that the Palette ram at $9c00-$9cff is not being written correctly. A good place to start checking this is to look for the select signal that comes from the 74LS139 @2S pin 10 on the bottom board.
This goes into 74LS138 @ 8D pin 5 on the top board and generates the read / write signals for the palette ram.
The 74LS08 also has 2 gates used with these select signals, pins 8-13, these control the data buffers enable and direction control.
Retroman839
Senior Member
Most appreciative of your input,
I just jumped to scope as I thought it could instantly show good input on the pins you requested to see ,
I read that Pallet ram sets the vídeo sync signal which also triggers the sound circuit ?
I have just made an áudio probe and been probing the sound chips as I also have no sound ,
I’m getting some sound effects from 1 pin. Of one chip only , No music ..
“Slice project “
I did save a folder ,
Once I save a folder to a location and name it - Does each slice automatically get saved to the folder ?
Or do I need to save after each slice then choose the location to save too ?
I just jumped to scope as I thought it could instantly show good input on the pins you requested to see ,
I read that Pallet ram sets the vídeo sync signal which also triggers the sound circuit ?
I have just made an áudio probe and been probing the sound chips as I also have no sound ,
I’m getting some sound effects from 1 pin. Of one chip only , No music ..
“Slice project “
I did save a folder ,
Once I save a folder to a location and name it - Does each slice automatically get saved to the folder ?
Or do I need to save after each slice then choose the location to save too ?
GadgetFreak
Active member
The Palette ram has nothing to do with video sync or sound control, not sure where you got that idea.
The address decoding cascades through several 74LS139 & 74LS138's.
So for palette ram the select is from 3M -> 4M -> 2S (all on the bottom board).
For Slice the Folder button allows you to select the root folder for Slice Projects.
Then each Slice Project you create will occupy it's own sub folder. Each IC / Result / Raw data will be in it's own file.
The address decoding cascades through several 74LS139 & 74LS138's.
So for palette ram the select is from 3M -> 4M -> 2S (all on the bottom board).
For Slice the Folder button allows you to select the root folder for Slice Projects.
Then each Slice Project you create will occupy it's own sub folder. Each IC / Result / Raw data will be in it's own file.
Retroman839
Senior Member
So can I slice the 139’s & 138’s
@ 3m 4m 2s.
And see if I have a fault in these 3 ic ?
@ 3m 4m 2s.
And see if I have a fault in these 3 ic ?
GadgetFreak
Active member
Yes as a start.
If none of these are bad you should work through all the IC's on page 8 of the schematic as this is where the bitmap data is given colour and sent to the display. All these IC's are on the top board with the edge connector.
Retroman839
Senior Member
Cheers for the schimatic👍
This should keep me busy for a while ..
Will report slices as I go
This should keep me busy for a while ..
Will report slices as I go
Retroman839
Senior Member
O k
Slicing again on bottom pcb
@ 4 m .
I have left propergation at default 50ns
Float check reported 0 floating pins 👍
Slicing again on bottom pcb
@ 4 m .
I have left propergation at default 50ns
Float check reported 0 floating pins 👍
Retroman839
Senior Member
Retroman839
Senior Member
Só I have just bought Sukbir’s
Identical bootleg só I can compare slices with a working board.
This will help for comparison
Identical bootleg só I can compare slices with a working board.
This will help for comparison
Retroman839
Senior Member
Just built phil murr áudio probe also to help me with the no sound…
Pots from my old stock,
they are massive but correct value ..
Tested & working great👍
Phill murrr áudio probe Só
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Retroman839
Senior Member
Áudio probe already doing its magic ..
I have full sound at first leg on left of the amp,
Só bad amp ?
Input ok
No output .. shorted amp ?
All the other pins are dead except pin 7 from left high pitch squeal
I have full sound at first leg on left of the amp,
Só bad amp ?
Input ok
No output .. shorted amp ?
All the other pins are dead except pin 7 from left high pitch squeal