Battlezone
Active member
Symptoms #1
No power to PCB
Examined the audio regulator board (AR-II) had burnt out R30 and
damaged R29.
Fix #1
Did the sense mod (replaced the resistors with wires and will adjust
the voltage manually).
Symptoms #2
Stable "rug" pattern across the screen, no sign of CPU
activity in the pattern.
Dead end
Tested the 6502 in another board but it was ok.
Fix #2
Measured the resistance across the pins of the reset
button and found it was stuck on. Pressed the button
a few times to release it.
Symptom #3
Graphics corruption on sections of the screen and on the moving
objects. Failed the built-in RAM check in test mode (which doesn't
help localize the fail).
Fix #3
Piggy backed the 2101 RAM chips in pairs. K3/K5 looked suspicious.
De-soldered these chips. Can confirm K3/K5 control the even rows on the left
side of the screen (which is what was corrupted). Here's a
picture (the top is on the left in this photo).
Proceeded to de-solder and socket all the 2101 VRAM chips.
Here is the mapping.
H3/H5: left side, odd rows (1, 3 ...)
J3/J5: right side, odd rows
K3/K5: left side, even rows (2, 4 ...)
L3/L5: right side, even rows
When the chips in column 3 are bad one region tends to get
filled with letters (typically 'E's). When a chip in column
5 is bad you tend to get solid blocks with circular shape in it.
When both are bad (removed) you tend to get solid blocks
(see the picture above).
Now that I have the mapping going back to the symptom #3
picture we can now see the issue is on even rows on the left side
of the screen, and we can see the solid block with a circular shape in.
Which implies that K5 was the problem chip.
I replaced a bad 2101 chip, tested all my spares and the
game is 100% working (the sprite issues were resolved by this too).
Battlezone2016-04-12 00:45:23
No power to PCB
Examined the audio regulator board (AR-II) had burnt out R30 and
damaged R29.
Fix #1
Did the sense mod (replaced the resistors with wires and will adjust
the voltage manually).
Symptoms #2
Stable "rug" pattern across the screen, no sign of CPU
activity in the pattern.
Dead end
Tested the 6502 in another board but it was ok.
Fix #2
Measured the resistance across the pins of the reset
button and found it was stuck on. Pressed the button
a few times to release it.
Symptom #3
Graphics corruption on sections of the screen and on the moving
objects. Failed the built-in RAM check in test mode (which doesn't
help localize the fail).
Fix #3
Piggy backed the 2101 RAM chips in pairs. K3/K5 looked suspicious.
De-soldered these chips. Can confirm K3/K5 control the even rows on the left
side of the screen (which is what was corrupted). Here's a
picture (the top is on the left in this photo).
Proceeded to de-solder and socket all the 2101 VRAM chips.
Here is the mapping.
H3/H5: left side, odd rows (1, 3 ...)
J3/J5: right side, odd rows
K3/K5: left side, even rows (2, 4 ...)
L3/L5: right side, even rows
When the chips in column 3 are bad one region tends to get
filled with letters (typically 'E's). When a chip in column
5 is bad you tend to get solid blocks with circular shape in it.
When both are bad (removed) you tend to get solid blocks
(see the picture above).
Now that I have the mapping going back to the symptom #3
picture we can now see the issue is on even rows on the left side
of the screen, and we can see the solid block with a circular shape in.
Which implies that K5 was the problem chip.
I replaced a bad 2101 chip, tested all my spares and the
game is 100% working (the sprite issues were resolved by this too).
Battlezone2016-04-12 00:45:23
