Galaxy S4 external speaker detailed troubleshooting

A

AC Question

My Sprint Galaxy S4 (SPH-L720, 4.2.2, rooted) was completely immersed in fresh water for about 15 minutes. I took the battery out, put it in a bag of rice and as soon as I could (three days later) took it to a local cell repair store where they cleaned (using some kind of solvent) and returned it in a couple of days.

Everything now works on the phone except the external speaker. I will not return to the repair place for a variety of reasons so I am trying to fix the speaker myself.

Checked and double checked all sound settings and everything is set to have the speaker play all typical sounds. Also checked speaker function with the *#0*# test screen, headphones work fine, external speaker no.

I have booted in safe mode (no help) and booted into recovery mode to wipe system cache, also no help.

Took phone apart and tested speaker itself by applying an audio signal to the two terminal pads and the speaker works fine. Applied ear bud speaker wires directly to the two gold spring contacts that touch the speaker pad and get nothing. Using a voltmeter, I get about 20mv signal from headphone jack, but nothing from the gold spring contacts (with no headphone jack inserted of course).

Removed "daughterboard" (or USB board, whatever you want to call it) ribbon connector from motherboard and looked at connectors under magnification and nothing looks amiss. Firmly reseated connector but still no external speaker.

So, seems to me that the audio signal is just not making it to the gold contacts for the external speaker. Perhaps I need a new daughterboard with new ribbon connector. Any other ideas?
 

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