Performa 275 (CCII) w/ LC 550 board - Distorted sound in one channel

[callanbrown]

Hi folks,

I have a Performa 275 (ie Japanese Color Classic II) but I think it's actually an LC 550 motherboard inside, owing to the onboard VRAM being 512KB (I'm assuming this because I get "thousands of colors" with nothing in the extra VRAM slot).

Anyway, I turned the machine on this morning and one of the two channels (the one connected to the speaker output) is extremely distorted and is pulling in electrical noise as well. When I plug in speakers, one channel is fine but the other is heavily distorted like it's majorly clipping. Board has been recapped and I tried resoldering the '0129 (but I didn't remove/clean under it).

I checked this back to the 129 chip to verify that indeed the audio coming from the chip is already distorted, so it doesn't seem to be related to the few components after the chip.

Is the problem likely the 343S0129? Searching around I'm not getting many hits on distorted audio (vs no or low audio).

 

[jajan547]

This is Common on Color Classics it’s the internal speaker causing this issue. Happens on my color classic ii as well.

 

[callanbrown]

I disconnected the speaker to check, issue remains on line out. Just now I even tried removing the amp from the analog board to see if that was feeding back somehow but no luck.

 

[jajan547]

I disconnected the speaker to check, issue remains on line out. Just now I even tried removing the amp from the analog board to see if that was feeding back somehow but no luck.

Is there cap goo possibly under anything?

 

[callanbrown]

When I recapped the board nothing was yet leaking, I suppose I'll eventually remove the '0129 to check. I would be surprised since the issue just popped up like yesterday.

 

[jajan547]

When I recapped the board nothing was yet leaking, I suppose I'll eventually remove the '0129 to check. I would be surprised since the issue just popped up like yesterday.

My guess is a chip is connected but maybe a pin is not fully attached. Have any photos?

 

[callanbrown]

My guess is a chip is connected but maybe a pin is not fully attached. Have any photos?

Appreciate that but theres only one chip related to sound as far as I can see, the one I mentioned, and it's been resoldered.

 

[jajan547]

Hmmm okay now maybe a break right before a pad, pads before a trace entered have a dip liek a mini ditch are you positive everything around that chip is okay?

 

[callanbrown]

Again thanks for your offer to help, but I am an Electrical Engineer and fix arcade boards on YouTube etc (channel 74XX), I have done all the usual checks. Just really hoping someone can say whether or not swapping the 0129 might have a chance of fixing it or not.

 

[jajan547]

Again thanks for your offer to help, but I am an Electrical Engineer and fix arcade boards on YouTube etc (channel 74XX), I have done all the usual checks. Just really hoping someone can say whether or not swapping the 0129 might have a chance of fixing it or not.

It’s not uncommon so it might do you have any spares or do you need to hunt one down?

 

[callanbrown]

Yes I'm going to have to find a replacement. It looks like a number of LC boards has them so maybe someone has an otherwise dead board I could scoop one from.

Someone in another thread mentioned they were able to buy some from somewhere so maybe I'll send them a PM.

 

[jajan547]

Yes I'm going to have to find a replacement. It looks like a number of LC boards has them so maybe someone has an otherwise dead board I could scoop one from.

Someone in another thread mentioned they were able to buy some from somewhere so maybe I'll send them a PM.

Hope this helps....link.

 

[callanbrown]

Lol, I'm afraid thats not helpful. I too can google the part name and find a hundred of these websites, they do not actually have these chips.

 

[jajan547]

Lol, I'm afraid thats not helpful. I too can google the part name and find a hundred of these websites, they do not actually have these chips.

Well I guess steal one off an LC

 

[callanbrown]

Follow up! Bought a cheap mobo for a Quadra 630 that had the 343S0129 chip. Swapped it in, problem fixed!

Let it be known a failure mode for this chip is distortion.