Duo R - crackling Left Audio after RGB mod

[yxlplig]

I'm having trouble comprehending what is going on with this Duo R. I'm using Voultar's Duo RGB board (the older blue one). Up until recently I was using CVBS as sync, but I decided to hook up csync.

The moment I connected pin 44 on the 6260 to Voultar's board I started getting all kind of cracking and popping out of my left speaker--for whatever reason I decided to test the system at this point--the csync is not hooked up to the DIN at this point, so I know nothing I did at the DIN is causing this problem. I eventually finish the mod removing the DIN, disconnecting CVBS, and wiring csync to the DIN in its place, the problem persists.

I did all the basic checks, different TV/speakers, different ac adapter, different video cables. I verified ground continuity for the power cord, scart cable, and the modboard. I scrutinized every one of my joints and all the components on the modboard with a USB microscope and found no issues. I don't understand how anything I did would affect the audio circuit like this.

Does anyone have any ideas about what this could be? Also the RGB output has been flawless throughout all of this. There has never been a single issue with the picture quality.

[yxlplig]

I'm thinking now that it was just a coincidence that this issue occurred after making changes to my RGB mod. I completely disconnected csync and reflowed pins 40-45 on the 6260 just to be safe and I'm still getting lots of cracking out of the left speaker. So it looks like I'll have to treat this as just an audio problem. Perhaps a capacitor or op-amp went bad.

EDIT: I have no idea anymore, I double checked my mod-work again and the crackling goes away when I fully disconnect my RGB amp (between the HuC6260 and the inputs of the modboard)

[NightWolve]

EDIT: I have no idea anymore, I double checked my mod-work again and the crackling goes away when I fully disconnect my RGB amp (between the HuC6260 and the inputs of the modboard)

Ah, interesting! The motherboard was fully recapped I assume BTW ??

[yxlplig]

EDIT: I have no idea anymore, I double checked my mod-work again and the crackling goes away when I fully disconnect my RGB amp (between the HuC6260 and the inputs of the modboard)

Ah, interesting! The motherboard was fully recapped I assume BTW ??

It actually has not been recapped yet. I've recapped all my other consoles of similar age except the Duo R, simply because it has a lot of capacitors and everyone always insists that the Duo R/RX never have bad caps.

[NightWolve]

It was the last in the factory line so its capacitors will die last from previous models but I don't trust the notion they're not part of the bad, leaky batches of that era. I'd go ahead and do it since you got the unit open. Maybe start with all the capacitors at the audio circuit and power area first but with the full intent to replace every one.

[yxlplig]

Evidently the issue was solely caused by my wiring. I quickly tacked in some 30 awg kynar just so that the console would output video again when I'm testing and when I turned it back on all the cracks and pops were gone. I did a full playthrough of a game and still no crackling sound.

It's really irritating because I did a really nice job before and this hack job I put together in 5 minutes works better. It's still interesting to me that this manifested as an audio issue. I know csync and Green were fine. The pins where Red and Blue are pulled from both have neighboring pins that are supplying +5v, perhaps that same rail supplies the audio circuit and somehow voltage from the R and B lines were shorting into it? There is a trace that supplies +5v to all the various pins on that side of the chip - that crosses my wiring, perhaps the solder mask on it was damaged. I really don't know though.

I will still replace the capacitors (eventually). There are so many though, there has to be at least 50 or 60 of them. I'll focus on playing some games for the time being, and then come back to this.

Also, I know this outcome kind of contradicts my original post, but I insist that there was a very comfortable air gap between all my original wiring, there was nothing bridged or anything visible that would indicate a short.