Performa 475 audio issue

[namprin]

I'm currently working on refurbishing a Performa 475, and have run into an issue. Before recapping the machine, it would boot to the desktop, but it would not make a boot chime. I went into Sound control panel, and after turning the volume up to max, I could faintly hear some of the louder sounds like "Indigo" coming through the speaker. I chalked it up to capacitor issues, as I had seen something similar on an SE/30 before recapping.

After the recap/cleaning of the board, the issue remains. The sound works but is VERY faint. If I connect headphones to the audio jack, I can hear the boot chime, but just barely. I can't really hear it through the speaker, but alert sounds are still faintly audible if the sound is all the way up.

I also remember that I had done the resistor hack on another one of these machines a while back, and it worked, but it made it so that I couldn't install the OS easily (the installer didn't recognize what kind of machine it was anymore). I was curious if a previous owner had done the same thing, and sure enough, the resistors had been moved on the bottom of the board. I put them back (thinking the overclock may have messed with audio), but the issue remains.

Has anybody run into something similar or have any good ideas what to start looking at?

 

[Drake]

I've seen the sound drown out before/after recap when electrolytic was still living underneath some components.
A thorough bath and scrub had solved it for myself (maybe not your case as you've already cleaned it).
As far as the 33mhz resistor swap goes this should not affect the ability for OS installation if you are selecting "universal". Nor will the swap affect the sound.
Barring a good and proper cleaning maybe you can post some photos with close ups for us to view/inspect. Never hurts to have another set of eyes

 

[namprin]

Awesome to think you had one of these back in '95. I think I was rocking a 6100 back then.

I am currently giving the motherboard another bath in alcohol, as per Drake's suggestion (can never be too clean), so I will have to wait to test until it is completely dried out.

I had tried to do PRAM reset a few times, but I for sure didn't try 10 times. I will give it a shot when I put it back together.

It does have a new PRAM battery, and I had tried the CUDA button, but that didn't seem to have any effect. It is funny, as my other 475 doesn't even have this button. There are pads on the board, but no button. Other than that, the boards look identical.

Thanks for the responses, guys!

 

[Mac84]

In situations like this I would suggest to carefully check your capacitor work around the sound chip area. In addition, I've experienced a LC 575 board which had a similar issue. It turns out there was a break in a trace near one of the capacitors that was impossible to see without my microscope.

So I wouldn't rule out a bad trace, or maybe there could be a bad connection to the sound chip. But keep looking at the board, you'll find the culprit eventually!

 

[Kay K.M.Mods]

I Agree with Mac84, Perhaps... there is a problem with the sound chip itself. I have an LC575 and an LC475, The same is true for CC, which is a 030 machine, but the low-cost Macs of that generation usually have similar designs. If you try to remove the sound chip even if it doesn't look like a bad trace, the pins may have defective solder. And sometimes the bad traces are hidden under the sound chip.

The Pix r from CC, but when I removed the sound chip, the pattern was black and rusty, so I fixed it cleanly and re-soldered it. Of course the sound is back.

 

[namprin]

Well, I now have what is most likely the cleanest motherboard in my house
Still having the same issue that it was having from the beginning, however.
I have found that, if I press against the underside of the headphone jack with my finger, while a pair of headphones are connected, the boot chime will be audible when powering it on, but it is VERY faint, almost to the point that I can't hear it.
When the speaker is plugged in, what I get is a pop when I first power it on, and then nothing. It may be making the startup chime, but it is too faint for me to hear.
This pop happens on a known-good board of the same type, but is followed by the startup chime.
I am attaching images of the board, if that helps.
I think I agree with Kay K.M.Mods, that there may be an issue with the chip itself. What does everyone think? Should I try to remove it?

 

[pfuentes69]

Probably a silly question, but did you check the speaker? I had a bad speaker in my IIci, so these things happen…

For the record, I have also a funky issue with sound and my LC475. When I manipulate things inside sometimes I lost the sound… then I reseat the video memory and sound always come back until I touch the inside again… maybe is a broken trace or something… but as it mostly works I’m fine with it.

 

[namprin]

No such thing as a silly question for something like this. In my experience, the fix is often a simple thing that has been overlooked.
Yes, I am sure the speaker works. I have tried the one in the machine, as well as a test speaker that came out of a dead SE/30. That speaker works as expected when connected to my other Performa 475’s motherboard (known-good machine).

 

[max1zzz]

Another possible culprit is the headphone connector, it has a little switch in it that switches between the internal speaker and the headphones so it is possible that if the inside of the port is corroded neither the internal speaker no headphones will work correctly

 

[namprin]

I wonder what would happen if I removed the headphone connector completely? Would the internal speaker still work (if the issue was the jack)?

 

[max1zzz]

You would need to jump the pads that correspond to the switch or you'll get no audio at all, there isn't really any need to remove the headphone socket to so this

Assuming the 475 uses the same headphone socket as the I/II/III this is a suitable replacement: https://www.digikey.co.uk/en/produc...=N4IgTCBcDaIMIAUCMBaAzAVkwOQOItwCUVsAREAXQF8g looking at the datasheet of that you need to jump pins 2 to 4 and 5 to 3

 

[namprin]

So I bridged those pins by soldering wires between them. Behavior is the same when listening to the speaker. There is an initial POP sound, and then nothing.
If plugged in to headphones, it now sounds exactly like it did when I was pressing my finger to the pins for the headphone jack on the back of the board before. It is just as quiet, but I can still hear a little static, followed by the boot chime, but it sounds VERY quiet, like it is coming from very far away.

 

[namprin]

Well, just so I don't do anything too terribly stupid, I want to verify. The actual sound chip is the one in U30, correct? I am thinking of removing it with my hot air station and making sure it is clean under it, and then soldering it back into place.

If that doesn't work, does anyone know of another machine that uses the same chip? I may have to go looking for a donor. I have another, working Performa 475, but I don't really want to remove the chip from that.

 

[BusError]

I just got a LC475 from @Kai Robinson -- it has that issue -- did anyone found a likely cause? I could rework the audio chip but if there's an alternative solution...?

 

[fred1212]

Hi I've a similar problem no sound from speaker but sound from the headphone jack. The speaker works checked on another LC