DK PCB making background "siren" noise

TheYeti

Well-known member
Joined
Sep 3, 2015
Messages
5,699
Reaction score
5,326
Location
Centennial, Colorado
I just recapped my Sanyo 20EZ and everything seemed to go fine. I've got the picure dialed in very nice now. I also recapped the audio board. So the image looks very nice. (Still need to adjust the B+ though)

BUT...

There is a constant hum mixed with a "wawawawa" sound coming from the speaker. It's proportional to the volume level. The louder I turn up the volume POT, the louder the hum/wawawa sound is.

Here is a video I took of that sound: https://www.youtube.com/watch?v=vl1bEBO3RjM

(note that only DK's stomping is heard, I later fixed that by turning up the volume POT on the DK board itself)

I bought this DK a few months ago and the sound never worked when I got it so I'm not sure if it was like this before or if I did it with the recap.

Please help me. I'm cold and crying in the corner.

Oh and another hint: Jumpman sounds a little odd when he jumps. Like the jump sound effect is flat or skewed in some way.
 
Last edited:
Do you hear the wah sound if the volume pot on the game pcb is turned all the way down?

Do you hear it if you disconnect the game pcb?

It would be good to narrow the source down to the amp or the pcb. I suspect it's coming from the pcb, I've seen it a couple of times in the past and if I remember correctly one of the transistors in the sound circuitry was flaky. I think my dk jr still does it actually, but turning the volume down just a smidge makes the wah inaudible while the rest of the game sounds great.
 
Thank you so much hindered for you reply. But I've actually made it worse.

I feel like an idiot because in an effort to try different things, I unplugged the "9P CPU" cable from the power supply and plugged it back in. Unfortunately, I wasn't paying attention and did this while the cab was powered on.

So the good news is that the hum and the wah-wah sound are gone now. However, the bad news is that I don't have ANY sound now. Regardless of adjusting either sounds pots.

The screen still looks fine and the game plays though.

Did I fry something on the PCB when I plugged that cable back in while the machine was on?
 
I'd look to see if the DAC08 is pulsing. And the 8035 before it. Both on the CPU pcb.

Harm shouldn't come from that though. However, that's what generates the sound.
 
I'd look to see if the DAC08 is pulsing. And the 8035 before it. Both on the CPU pcb.

Harm shouldn't come from that though. However, that's what generates the sound.

Sorry, this is something I'm not familiar how to do. Can you explain how I do this?

Sorry, this is all new to me and I'm diving in head first but I'd love to get to the bottom of this.
 
Sub 20$ off eBay or Amazon is more than sufficient for this.

You will then need to pull the data sheets for each chip.
8035 is socketed, so many will just purchase a new one and replace, with their fingers crossed.

The DAC is soldered to pcb with no socket. If you have a soldering iron and a way to remove solder, that's most likely the culprit. The DAC is a quad output, but only uses 2 of them.

The right equipment can add up, depends on how deep you want to go. ;)
 
I don't think connecting the cable would do harm unless you did it backwards or you saw sparks or whatever.

I vaguely remember something about jb and jc connectors. They are interchangeable and can do bad things if you switch them around. Are yours correct after switching stuff around?

And yes a logic probe will be helpful in figuring out if the board is trying to put out sound. I think there are two sets of sound on this board too. Analog sound (like the jump sound) and the discrete sound (like DK stomps). I'm sure someone will correct me if I'm wrong. But that could explain why you heard stomps but not other sound.
 
Yes certainly got that cabled plugged back right where it came from. No sparks or popping sounds either. In fact, I did it once successfully and the sounds stopped. Of course the screen went white as expected. Then I plugged it back in and the sound came back on. As a matter of fact, I caught the whole thing on video the 2nd time I did it and that is the time that the sound didn't come back on. Here is the video:

https://www.youtube.com/watch?v=1f20sBbQ-_o&feature=youtu.be

The video above was an attempt to show that the buzz/wah sound would stop when I unplugged that cable. But when I recorded it, this was literally the last time I heard sound at all.

Well now I have the 2-board set removed from the cab so that I can Identify the chip that might be bad. Maybe I'll put It back in again and make sure everything is connected properly and try again. I've got a sneaky feeling it's one of those 2 chips on the PCB tho.
 
Well, hooked everything back up and triple-checked my connections everywhere. Same story...screen comes on and game plays fine, just no sound at all.

I'm really bummed because my recent cap job made the screen look fantastic.

I'll update this thread after I pick up a logic probe.

Huge thanks to both of you for helping me thus far. I'm new to all of this but doing my best to do what you say. I've come this far, might as well fix everything.

I will probably need more hand holding when the logic probe arrives.

Good news is that I feel my soldering was good on the caps so if I have to solder on the PCB, I think I can do it.

thanks again, I'll be back. :)
 
I wonder if it's bad solder/bad cable on the connector you were fiddling with. Could, in theory, be the pot too. A logic probe will go a long way.

This is a frustrating hobby sometimes. Stick with it and you'll get it working.
 
I wonder if it's bad solder/bad cable on the connector you were fiddling with. Could, in theory, be the pot too. A logic probe will go a long way.

This is a frustrating hobby sometimes. Stick with it and you'll get it working.

Thanks again hindered. I'll have to keep all of these possible culprits in mind until the logic probe arrives. Here is the one I ordered:

http://www.amazon.com/gp/product/B0002E7X5O?psc=1&redirect=true&ref_=oh_aui_detailpage_o00_s00

Should arrive to me on Wednesday. You should hear back from me sometime after then.

I'm a little overwhelmed with all the possible causes but the silver lining is that I'm learning a few things!
 
My Logic Probe arrived. I've watched a few videos on how to use it but they are sorta vague. I'm pretty sure that I have to hook the alegator clips up to power and ground but I'm not sure where those connection points are at.

Also does the logic probe get set to 400PPS or 0.5PPS?

I downloaded a DK schematic but I'm still trying to find the DAC08 and the 8035

As you can tell, I'm like a fish out of water here. :)

Also, I don't have a proper test bench so I'll have to probe everything with the PCB in the cab itself. yay!
 
http://forums.arcade-museum.com/showthread.php?t=361502&highlight=Logic+probe

Good information there. Watch the video for sure. I don't know what setting you need but your manual will probably tell you what to do for ttl chips.

I think there is a ground test post on the Nintendo pcbs. You can hook your black lead there. My probe is self powered so I don't need to hook to 5v. I assume you can hook to the positive side of a cap that meters 5v but someone will probably chime in to say how dumb that is!

Basically, for narrowing down your problem, I would study the schematic and find out where you should see output activity for sound prior to going to the amp on the monitor. If you are seeing it, the problem is with the amp. If you aren't seeing it, you'll need to study datasheets and trace the problem backwards until you find the faulty component/s
 
Thanks for sticking with me hindered!

I just looked at your last post this morning so I'll have to check out that thread and video.

In the mean time, I have more updates. I looked up the pin-out on the DK Jamma edge. I found the ground pins and 5v pins so I just hooked up the alligator clips to those. Really easy. (See image attachment to this post)

I was also able to locate the DAC-08 chip and started probing it. Some legs were hi and some legs were low. (I was expecting the light to flcker on and off)

But then I realized that when you first turn on a DK cab, there is a quick "boing" sound and then it sits idle with no sound until you play a game. So, the DAC-08 chip was just sitting there waiting. So I coined up and started a game, then walked back and probed the chip when I knew sound would be playing. And I got some activity. Some legs (and a few others) started rapidly flipping between hi and low. And If I watched closely, I could almost tell it was exactly to the cadence of DK sound effects.

Here is a quick video I shot of this exact test above. In the video you will notice that when I first power on the cab, the DAC-08 is just sitting there. Depending on what leg I probe it's either high or low. But when I coin up and start a game, the DAC-08 "comes alive"

https://www.youtube.com/watch?v=z8MkDaRnsgY&feature=youtu.be

Does this possibly mean my DK pcb is actually OK? Perhaps it's the audio amp that is the culprit?

I took out the audio amp and looked it over last night again. I can't find any obvious problems with the cap job I just did on it. However, it would further support the theory as I'm not getting ANY sound. No hum, no buzz. Nothing. It's dead as dead can be. Almost like the speaker is unplugged but I have checked that of course.

I actually have a new speaker coming from Mike's arcade soon so I"ll rule that out.

I see that Twisty Wrist has a repo Nintendo amp that I could throw in there:

https://www.twistywristarcade.com/twa-repro-mfg/966-nintendo-audio-amplifier-.html
 

Attachments

  • IMG_4429.JPG
    IMG_4429.JPG
    101.6 KB · Views: 13
Last edited:
Yes, if your PCB is outputting activity at the end there, I'd start with the assumption that your PCB is OK (or at least generating _some_ sound).

That leaves your sound amp, speakers, and wiring that goes in between. You should ohm out your speakers & check the wiring for continuity, just to rule it out.
 
Back
Top Bottom