Mac LC with no sound?

[classic_bigmac]

Hi All, was hoping to get some direction after a long struggle with getting the sound working on my LC I have run out of ideas? So far the following has been done:
1. full recap of board and TDK PSU (psu had a broken R51 resistor on top of leaking caps) but is working now
2. checked all traces /via's from sound chip all good
3. Speaker tested working but also tried another speaker still nothing
4. headphone jack no sound
5. pram battery new
6. Board is very clean, no corrosion

What I have noticed is that the speaker will make static noise when hdd, sdhdd or even floppy drive are operating?

Anyone have any suggestions I can try?

Thanks in advance

 

[jajan547]

Did you check under the chip? Cap goo likes to get in there and will eat some vias.

 

[joshc]

Got any photos of your board please? Making sure the Apple sound chip is clean underneath is important.

 

[classic_bigmac]

I have washed the board and tried to clean under the sound chip with flux remover but don't have equipment to remove it, does anyone have any photos or schematic of whats underneath?
Is it common for these to fail as I may try to source a replacement...will try and get some photos of the board

 

[jajan547]

Here's the schematic but use desoldering wick to remove it if you don't have hot air.

 

[bibilit]

The Dfac chip can be bad, but not usual.
Have you had a look at the other side of the board ? happened to me a couple of weeks ago on a Classic II board, a broken trace where i was not looking.

 

[classic_bigmac]

I have checked most traces (front and back) and so far all have been good, the schematic is a great help and again all the traces from the sound chip are good.

I have the low melt solder on order so will try removing it and checking/cleaning underneath and report back but my gut feeling is its gone bad. I still get static noise when sdhdd is running (almost sounds like a real hdd noise) which is strange? I have usually fixed the sound after a recap on the earlier macs but seems like the LC loss of sound is common even after a recap.

 

[jajan547]

I have checked most traces (front and back) and so far all have been good, the schematic is a great help and again all the traces from the sound chip are good.

I have the low melt solder on order so will try removing it and checking/cleaning underneath and report back but my gut feeling is its gone bad. I still get static noise when sdhdd is running (almost sounds like a real hdd noise) which is strange? I have usually fixed the sound after a recap on the earlier macs but seems like the LC loss of sound is common even after a recap.

Yeah it’s not uncommon, I’d imagine a good clean should fix it.

 

[classic_bigmac]

UPDATE - removed the sound chip and tested all the traces and vias underneath all were good, infact it was very clean underneath. Even tried it without the sound chip and the LC still worked but as usual with no sound. Is there any other areas on the board to check while I try find a replacement sound chip..

 

[jajan547]

I have a recapped LC II Board if you can’t find said chip, I still think there’s something not connected or trace break look over that schematic.

 

[mitchkramez]

I don't know how close it is to the LCII, but I ran into this on my LCII that may be worth looking at: https://68kmla.org/bb/index.php?threads/lc-ii-no-sound-after-recap.886/post-428146

 

[Amiga of Rochester]

Shoot some photos to me. I might be able to look at it for you if you're in USA.

 

[joshc]

Some photos of the board would be useful, there might be something you've missed.

 

[imactheknife]

I just recapped an lc, sound worked fine. Next day, nope. Decided to pull off ub10 dfac and it was filthy underneath. Scrubbed pads with flux and wick, then cleaned area with isopropyl. Let dry, then prepped pads. Also, cleaned chip and prepped legs for reentry lol.. better now

 

[imactheknife]

Ub10 off