linx310
Active member
Donkey Kong "siren" problem (not the nintendo hum!)....
Ok I am trying to figure what exactly causes the "siren" or "alarm" sound issue on Donkey Kong board stacks.
Video with audio from another member showing the issue
https://www.youtube.com/watch?v=vl1bEBO3RjM
Past threads covering the issue from various forums:
http://www.johnsarcade.com/forum/index.php?topic=2960.0
http://forum.arcadecontrols.com/index.php?topic=148896.0
https://forum.arcadeotaku.com/viewtopic.php?t=31442
https://forums.arcade-museum.com/showthread.php?t=368745
https://forums.arcade-museum.com/showthread.php?t=364831
Generally it is accepted that replacing Q4 or Q6 C1815 transistors will solve the issue. On some boards it works and others it does not.
I have 2 boards that have this issue. On both I replaced not only Q4 and Q6 but all the audio C1815 transistors (Q1-Q6). On one of the boards I also replaced the audio caps.
I checked 6L (the driver that activates the analog sounds) with a scope and it's not pulsing randomly so that's not it.
I checked out the switching Diodes D6 and D7 and they are behaving.
Stumped I decided to disconnect portions of the audio circuitry to see if I could isolate the cause.
Surprisingly it may not be part of the sound circuitry at all. We may have just assumed it was since it kind of sounds like a jumping sound. I disconnected the following which are marked in red on schematic I posted
R1 removed digital sounds.
R24 removed jump sound.
R2 removed donkey Kong stomping sound.
R14 removed walking sound.
I even removed the digital audio chip and CPU from the board.
I also swapped out video boards with others on board stacks that do not have this issue. No change so it is coming from the cpu board.
The "siren" sound is still present. If I disconnect capacitor C13 the sound disappears but this breaks the connection to the trace that the audio out is on so you can't hear anything anyways.
I have put the board in a stock DK cab and connected it to my supergun with one of Mike's DK to Jamma adapters (has a built in audio amp) and the sound is present in both so it is coming from the pcb.
Since past threads have always focused on the audio circuitry trying to solve this issue I wonder if that was a wild goose chase and the actual problem is noise coming from the one of the ICs on the board.
Perhaps a filter cap some place on the board is going bad or has failed?
Ok I am trying to figure what exactly causes the "siren" or "alarm" sound issue on Donkey Kong board stacks.
Video with audio from another member showing the issue
https://www.youtube.com/watch?v=vl1bEBO3RjM
Past threads covering the issue from various forums:
http://www.johnsarcade.com/forum/index.php?topic=2960.0
http://forum.arcadecontrols.com/index.php?topic=148896.0
https://forum.arcadeotaku.com/viewtopic.php?t=31442
https://forums.arcade-museum.com/showthread.php?t=368745
https://forums.arcade-museum.com/showthread.php?t=364831
Generally it is accepted that replacing Q4 or Q6 C1815 transistors will solve the issue. On some boards it works and others it does not.
I have 2 boards that have this issue. On both I replaced not only Q4 and Q6 but all the audio C1815 transistors (Q1-Q6). On one of the boards I also replaced the audio caps.
I checked 6L (the driver that activates the analog sounds) with a scope and it's not pulsing randomly so that's not it.
I checked out the switching Diodes D6 and D7 and they are behaving.
Stumped I decided to disconnect portions of the audio circuitry to see if I could isolate the cause.
Surprisingly it may not be part of the sound circuitry at all. We may have just assumed it was since it kind of sounds like a jumping sound. I disconnected the following which are marked in red on schematic I posted
R1 removed digital sounds.
R24 removed jump sound.
R2 removed donkey Kong stomping sound.
R14 removed walking sound.
I even removed the digital audio chip and CPU from the board.
I also swapped out video boards with others on board stacks that do not have this issue. No change so it is coming from the cpu board.
The "siren" sound is still present. If I disconnect capacitor C13 the sound disappears but this breaks the connection to the trace that the audio out is on so you can't hear anything anyways.
I have put the board in a stock DK cab and connected it to my supergun with one of Mike's DK to Jamma adapters (has a built in audio amp) and the sound is present in both so it is coming from the pcb.
Since past threads have always focused on the audio circuitry trying to solve this issue I wonder if that was a wild goose chase and the actual problem is noise coming from the one of the ICs on the board.
Perhaps a filter cap some place on the board is going bad or has failed?
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