DUO sound problems...again!

[omnedon]

With the failure of the capacitors being linked to how close they are to the heatsink and what not, would it work to not cut the capacitor short, place insolation over the wires, and have them bend away from the heatsink? I have yet to work on a duo, but I figure would this work out?

I see the proximity to the 'warm' heatsinks as secondary to the crap quality of the caps. There is not enough heat there to damage healthy caps, IMO. The heat doesn't help, but IMO crappy caps are the real issue. All over the board, including failed ones nowhere near the heatsinks.

[SnowKitty]

I see the proximity to the 'warm' heatsinks as secondary to the crap quality of the caps. There is not enough heat there to damage healthy caps, IMO. The heat doesn't help, but IMO crappy caps are the real issue. All over the board, including failed ones nowhere near the heatsinks.

this is true, supposedly there was a bad batch of caps going around back then. ive seen game gears have leaked caps (not just the sound ones) and ive seen some leaked caps in duos other than the ones near the heatsink

[omnedon]

It's back here now.

Indeed, the sound was gone, again. I took another look at the audio circuit, and the array of caps. I've replaced another batch of caps (10 more) and the sound is back. However, it's quirky. When the unit is cold, the redbook audio seems to need a 4- 8 second warmup for the sound to reach correct volume and fidelity. Once reached, it seems stable, but this 'warmup period' is still annoying me.

I'm beginning to question the op amp itself, as most of the audio related caps are now new.

As far as the burning smell described, there is no evidence of any short circuits, or melted anything. Everything is as shipped, except for the quirky audio. I'm not sure what to make of that. The region mod works perfectly (and is making troubleshooting so much fun with this mod already installed =) ).


I'm stress testing the longevity of the audio now.

[XYXZYZ]

Speaking of the opamp, is that a common one? Is it hard to find a replacement?

[FABombjoy]

Indeed, the sound was gone, again. I took another look at the audio circuit, and the array of caps. I've replaced another batch of caps (10 more) and the sound is back. However, it's quirky. When the unit is cold, the redbook audio seems to need a 4- 8 second warmup for the sound to reach correct volume and fidelity. Once reached, it seems stable, but this 'warmup period' is still annoying me.

Figure it out, will ya? I've got one that does that too, but all audio (not just CD). Haven't had a ton of time recently to fully diagnose it. The lack of schematics doesn't help... I tried to draw up the audio circuit but my eyeballs almost fell out.

One interesting quirk - originally it was the opposite. 8 seconds of audio followed by silence. If I shorted the input/output leads on that balance control IC (the standy-uppy guy to the right of the op-amp), audio would come back for a split second.

Somewhat related trivia: I measured some of the OEM caps from a recent Duo that I worked on. Most of them still read the correct capacitance, but had really really high ESR.

[omnedon]

This DUO hates me. I hate it.

However, I am the BOSS, and I will demonstrate this fact to this DUO.....

[RadiantSvgun]

Hmm, so its the unit itself that sucks. How about that? I should have invested in a Duo-RX instead.

If it gives you too much trouble, hit it with a hammer.

[FABombjoy]

However, I am the BOSS, and I will demonstrate this fact to this DUO.....

Well, I don't know if you ended up giving your duo the Tony Danza, but... uh... anyway

So, I got mine to work. Chances of it being the same problem are slim-ish, but FWIW, ensure that you have ~3.6V at the + side of C322 (3 caps to the left of the OKI chip). Turns out that on my Duo, C322 had leaked just a little bit and corroded the through-hole for R321. I cleaned it up and fixed it with a bit of wire. Good as new!

How I got there: I was probing my way back through the audio circuit with a logic pulser (makes a nice test-tone for the audio hardware) when I discovered that feeding a square wave into C322 turned the audio on.

[omnedon]

Thanks for that. I have a few stubborn boards here, and I'll look into that.

Radiant ended up getting a whole new mainboard, region modded again. Yikes. However, taking care of his problem was a higher priority than making sure I didn't lose on the deal. I can use boards like his for R&D, which helps out in the end.

Problems teach as much as successes do, sometimes even more.

[turbokon]

Mine had a similar problem. I was playing Lords of Thunder fine one day. Later that day, I thought I will play LOT again and my sound was static and would fade in and out randomly. I notices a terrible smell (not burning smell) but terrible. I opened my Duo and I could see which cap was bad. I replaced it. My sound came back and I left it on for two hours just to make sure no other caps needed to be replace and eventually the smell went away (due left over electolyte).

BTW, I'm starting to offer this type of service to. My post went a away because I'm a newbie, but you can find this post at http://www.pcenginefx.com/forums/index.php?topic=4953.0. I'm working on three units now, two include the sound fix.

[omnedon]

Turbokon, was it one of the regular silver surface mount caps, or was it one of the other ones?

[turbokon]

yeah, it was the third one down on the pre amp side, 22uf.

[omnedon]

No, on this DUO, I replaced that cap. And EVERY other surface mount cap on the board, with no change.

Now I've seen another with the same issue (all caps replaced, audio still bad). I solved the customers problems by replacing their mainboards altogether. Now these boards are for R&D.

The cap replace fix does not always work. It does a lot of the time, but not always.

[FABombjoy]

$25 to replace Duo caps AND ship the unit back? By the time it's all done and said, that's gotta be less than making minimum wage.

[omnedon]

Indeed, that is one hell of a price. He's out on his very own pricing tier.