dillingerradio
Enthusiast
Hello folks! I could use your help with Donkey Kong Jr., please!
The Issue:
Donkey Kong Jr. seems to be suffering from frequent, intermittent audio drop-outs, making it sound scratchy/crackly/static-y.
Example:
I have uploaded a clip of the intro (with sound) that you can hear here: https://imgur.com/38h43GU
You can see a visualization of this issue in the audio spectrogram in the provided image attachments on this post.
Work Done:
First it's probably important to identify that I am an amateur and still learning. I can not fluently read a schematic, but I am resourceful and picking it up as best as I can.
I have two copies of Donkey Kong Jr. which both have this same problem. The audio issue is as previously described (and demonstrated visually in the spectrogram image attached to this post): Audio frequently, briefly, cuts out. This causes the audio to sound bad. Insofar as the music and sound effects are concerned, they seem to play correctly, it's just cutting out. On one board, an additional problem is present in that the boot sound effect only plays intermittently.
With all that said, I attempted to look up the schematic information in my operators manual, which identifies that it's for the "DJR1-UP" model, "2 P.C. BOARDS TYPE." When reviewing the schematic drawing, though, I noticed that the alpha-numeric sector designations do not match my own board's layout. I do in fact have the 2-board type, but given my inexperience with schematics at large, I'm unsure if the mismatch is actually indicative of me having the wrong manual or not. I also took to the internet, where I found minimal resources (which is to be expected I guess, given the age of these boards and the general niche of arcade gaming). This is all a long form way of identifying that I'm unsure what constitutes the "digital audio" circuit on the board, so I am not 100% sure on where to look beyond the areas I've already identified.
Bearing that in mind, it seems the chip on spot 7K--an "MB3614 8217 M11" on my board, which is a quad op-amp that is functionally equivalent to an LM324--is often the source of audio troubles. From the resources I found, it was suggested to replace this with an LM324 chip. So, I piggy backed an LM324 on this spot (rather than fully replacing, for ease of troubleshooting purposes), and it yielded no improvement.
I then removed and cleaned the MBL8035N 8216 C55 audio CPU (commonly shortened to "8035") in spot 7H. I cleaned the pins with a fiberglass scratch pen, and flushed the socket with DeoxIT fluid before resocketing it. This yielded no improvement.
I then removed the chip at spot 3H (which contains the audio data) on the board, cleaning the pins with a fiberglass scratch pen, and flushing the socket with DeoxIT fluid before resocketing. As with the audio CPU, this yielded no improvement.
I then thought that it may be a result of the amp circuit on the Nintendo-to-JAMMA edge adapter I was using. To rule that out, I purchased a different one which utilizes a different setup. This did not yield an improvement, and the same audio issue was present.
I have also completed a recap of the electrolytic capacitors on the board, as part of routine preventative maintenance that I intended to complete anyways. This, too, yielded no improvement.
From the resources I was able to find, it seems the DAC08 is quite resilient, and not typically associated with audio issues. Despite that, I ordered a replacement that I intend to try, but it has not yet arrived as of the time of this update. In the meantime, I intend to also try reflowing a number of solder spots to check that isn't the issue.
If anyone has any information that could help me to resolve this, I would greatly appreciate it. If you happen to know whether or not the manual I've got is correct or not for my revision? Perhaps where I might find the appropriate one if it isn't? The only other one I've found seemed to be for an entirely different revision. Or maybe you have familiarity with the digital audio circuit for DK Jr. and know of some troublesome areas that I can investigate? Really, any signposting would be great here- I just need to know where to look.
Thanks for your time.
The Issue:
Donkey Kong Jr. seems to be suffering from frequent, intermittent audio drop-outs, making it sound scratchy/crackly/static-y.
Example:
I have uploaded a clip of the intro (with sound) that you can hear here: https://imgur.com/38h43GU
You can see a visualization of this issue in the audio spectrogram in the provided image attachments on this post.
Work Done:
- Board recapped - no effect.
- New LM324 chip piggybacked on spot 7K - no effect.
- 8035 sound processor removed, cleaned, resocketed - no effect.
- Chip 3H (sound files) removed, cleaned, resocketed - no effect.
- Nintendo to JAMMA adapter swapped for a different design to ensure audio amp not at fault - no effect.
- DAC08 replacement.
- Board reflow.
First it's probably important to identify that I am an amateur and still learning. I can not fluently read a schematic, but I am resourceful and picking it up as best as I can.
I have two copies of Donkey Kong Jr. which both have this same problem. The audio issue is as previously described (and demonstrated visually in the spectrogram image attached to this post): Audio frequently, briefly, cuts out. This causes the audio to sound bad. Insofar as the music and sound effects are concerned, they seem to play correctly, it's just cutting out. On one board, an additional problem is present in that the boot sound effect only plays intermittently.
With all that said, I attempted to look up the schematic information in my operators manual, which identifies that it's for the "DJR1-UP" model, "2 P.C. BOARDS TYPE." When reviewing the schematic drawing, though, I noticed that the alpha-numeric sector designations do not match my own board's layout. I do in fact have the 2-board type, but given my inexperience with schematics at large, I'm unsure if the mismatch is actually indicative of me having the wrong manual or not. I also took to the internet, where I found minimal resources (which is to be expected I guess, given the age of these boards and the general niche of arcade gaming). This is all a long form way of identifying that I'm unsure what constitutes the "digital audio" circuit on the board, so I am not 100% sure on where to look beyond the areas I've already identified.
Bearing that in mind, it seems the chip on spot 7K--an "MB3614 8217 M11" on my board, which is a quad op-amp that is functionally equivalent to an LM324--is often the source of audio troubles. From the resources I found, it was suggested to replace this with an LM324 chip. So, I piggy backed an LM324 on this spot (rather than fully replacing, for ease of troubleshooting purposes), and it yielded no improvement.
I then removed and cleaned the MBL8035N 8216 C55 audio CPU (commonly shortened to "8035") in spot 7H. I cleaned the pins with a fiberglass scratch pen, and flushed the socket with DeoxIT fluid before resocketing it. This yielded no improvement.
I then removed the chip at spot 3H (which contains the audio data) on the board, cleaning the pins with a fiberglass scratch pen, and flushing the socket with DeoxIT fluid before resocketing. As with the audio CPU, this yielded no improvement.
I then thought that it may be a result of the amp circuit on the Nintendo-to-JAMMA edge adapter I was using. To rule that out, I purchased a different one which utilizes a different setup. This did not yield an improvement, and the same audio issue was present.
I have also completed a recap of the electrolytic capacitors on the board, as part of routine preventative maintenance that I intended to complete anyways. This, too, yielded no improvement.
From the resources I was able to find, it seems the DAC08 is quite resilient, and not typically associated with audio issues. Despite that, I ordered a replacement that I intend to try, but it has not yet arrived as of the time of this update. In the meantime, I intend to also try reflowing a number of solder spots to check that isn't the issue.
If anyone has any information that could help me to resolve this, I would greatly appreciate it. If you happen to know whether or not the manual I've got is correct or not for my revision? Perhaps where I might find the appropriate one if it isn't? The only other one I've found seemed to be for an entirely different revision. Or maybe you have familiarity with the digital audio circuit for DK Jr. and know of some troublesome areas that I can investigate? Really, any signposting would be great here- I just need to know where to look.
Thanks for your time.
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