Battlezone
Active member
Symptoms
Game fires up but no spinner control or sound.
Investigation
Read up a little on the internals, common sound/spinner problems of this machine
as it wasn't one I'd messed with before. Lots of posts talking about the battery
on the power supply board, which I wasn't aware of.
Yup sure enough mine was corroded to hell. I quickly snipped it off (and the
ones on a couple of spare boards I had that had also gone bad).
"... uh, molecular acid." "It must be using it for blood"
Checked the 12V supply which goes to both the sound board and
the spinner PCB. The 12V output was too low (7-8V even when not
under load) and didn't respond to the adjustment pot on the power supply board.
There are 3 main semiconductors in the 12V regulator (U1, Q102, Q101).
I picked the easiest Q102, found I needed to desolder it to test it properly,
found it was bad, so I replaced it (this is where things start to go wrong), tested the
board again and found the spinner worked for one screen then died again.
I then stupidly replaced U1 and tried again. So by now I have 3 dead Q102 transistors
(the original and the two I hastily replaced - what I should have done was
search down stream to the higher power transistor first). Sure enough Q101
was bad and was causing Q102 to blow. So I ordered some parts, cannibalized another
board for the moment and replaced Q102 again!! and Q101. This time the supply
was stable and adjustable. This is where I needed to hunt for possible shorts
on the 12V supply (but didn't).
Here's the board I cannibalized, the 12V circuit and the 5V
section both have 2N2905. U1 is the same part Atari use on AR-II etc.
12V is now steady without load, but it's tricky to probe when everything is
inside the cab. Oh for some probe points on the pcbs (Atari spoil us).
Spinner is still flaky and the board has no sound, but transistors aren't blowing
anymore.
Next I start checking the PCB to re-seat chips and connectors.
I read about the ribbon cables on these boards and sure enough mine
are in a terrible state.
... but no where near as bad as this poor inductor.
That's the inductor for the 12V supply input. At this point I finally start getting
my act together and probe the 12V rails to find I have a short to the ground.
This 12V PCB short is probably the root cause of all the problems (missing sound,
missing spinner, destroyed inductor and destroyed transistors on the power supply
board). I replace the inductor with a wire (for the moment).
A short between the 12V rails is much easier to find than one between the
the 5V rails, but it's still a daunting task even with my UK compatible
Hakko FR-300
.
I started by desoldering the 3900 (as I had some spares of those left over
from my Space Invaders fix), but that wasn't the short. I did another 14 pin
chip, no luck. I then switched to lifting one pin on the black plastic
decoupling capacitors and found the only short on my 3rd cap.
Removing the cap (for the moment) fixed the spinner and sound (which is
surprising given the state of the ribbon cables).
Not my finest detective work, but there it is ... mistakes and all.
To do
I bought a zero power SRAM to replace the 6116 at B2 but it doesn't
appear to work. Not sure why yet.
Battlezone2016-05-05 11:04:33
Game fires up but no spinner control or sound.
Investigation
Read up a little on the internals, common sound/spinner problems of this machine
as it wasn't one I'd messed with before. Lots of posts talking about the battery
on the power supply board, which I wasn't aware of.
Yup sure enough mine was corroded to hell. I quickly snipped it off (and the
ones on a couple of spare boards I had that had also gone bad).
"... uh, molecular acid." "It must be using it for blood"
Checked the 12V supply which goes to both the sound board and
the spinner PCB. The 12V output was too low (7-8V even when not
under load) and didn't respond to the adjustment pot on the power supply board.
There are 3 main semiconductors in the 12V regulator (U1, Q102, Q101).
I picked the easiest Q102, found I needed to desolder it to test it properly,
found it was bad, so I replaced it (this is where things start to go wrong), tested the
board again and found the spinner worked for one screen then died again.
I then stupidly replaced U1 and tried again. So by now I have 3 dead Q102 transistors
(the original and the two I hastily replaced - what I should have done was
search down stream to the higher power transistor first). Sure enough Q101
was bad and was causing Q102 to blow. So I ordered some parts, cannibalized another
board for the moment and replaced Q102 again!! and Q101. This time the supply
was stable and adjustable. This is where I needed to hunt for possible shorts
on the 12V supply (but didn't).
Here's the board I cannibalized, the 12V circuit and the 5V
section both have 2N2905. U1 is the same part Atari use on AR-II etc.
12V is now steady without load, but it's tricky to probe when everything is
inside the cab. Oh for some probe points on the pcbs (Atari spoil us).
Spinner is still flaky and the board has no sound, but transistors aren't blowing
anymore.
Next I start checking the PCB to re-seat chips and connectors.
I read about the ribbon cables on these boards and sure enough mine
are in a terrible state.
... but no where near as bad as this poor inductor.
That's the inductor for the 12V supply input. At this point I finally start getting
my act together and probe the 12V rails to find I have a short to the ground.
This 12V PCB short is probably the root cause of all the problems (missing sound,
missing spinner, destroyed inductor and destroyed transistors on the power supply
board). I replace the inductor with a wire (for the moment).
A short between the 12V rails is much easier to find than one between the
the 5V rails, but it's still a daunting task even with my UK compatible
Hakko FR-300
I started by desoldering the 3900 (as I had some spares of those left over
from my Space Invaders fix), but that wasn't the short. I did another 14 pin
chip, no luck. I then switched to lifting one pin on the black plastic
decoupling capacitors and found the only short on my 3rd cap.
Removing the cap (for the moment) fixed the spinner and sound (which is
surprising given the state of the ribbon cables).
Not my finest detective work, but there it is ... mistakes and all.
To do
I bought a zero power SRAM to replace the 6116 at B2 but it doesn't
appear to work. Not sure why yet.
Battlezone2016-05-05 11:04:33
