TomTom 730 GO GPS - No Speaker Audio - Page 1
Forum section: electronics / repair

author: hgg
author_rank: Frequent Contributor
timestamp: January 22, 2024, 01:39:33 pm
content: Hi,I have a TomTom car GPS unit that has been working fine for years and recentlythe speaker audio stopped working. The Line Out audio and the FM transmittingaudio are working fine, but no speaker audio. You can select the output from themenus. The speaker measures exactly 4 Ohms and the connector looks fine.The oscilloscope shows the sound wave on the line output but does not showanything on the speaker connector.I cannot identify these two small ICs. The speaker is connected via two zero Ohms resistorsto the 815L1 IC. I am not sure if its an amplifier or something else.Any ideas on how to proceed?Thanks.

author: wasedadoc
author_rank: Super Contributor
timestamp: January 22, 2024, 03:46:10 pm
content: Should not be too difficult to figure out that 815L1. it is an 8 pin chip though 1 pin appears to be NC.2 pins for the speaker, H-bridge type output. Easily traced by PCB tracks.2 pins for power. Switch off and use Ohmmeter to find ground. Switch on and use voltmeter or scope to find +ve power.1 pin for audio in. Use the scope to see to see if one of the 3 remaining pins has audio going in.Expect both speaker pins to be at same voltage and around half of chip supply voltage.IC might be similar tohttps://datasheetspdf.com/pdf-file/1111491/WELLKINGTECHNOLOGIES/MIX2018/1

author: hgg
author_rank: Frequent Contributor
timestamp: January 22, 2024, 04:19:52 pm
content: Indeed, just before your reply I found that the audio signal is comingon the far right resistor. It is a 1K resistor followed by a 141K resistor!In the middle there is a capacitor to ground. With full volume the signal atthe first resistor is 1V peak to peak. There is no short on the IC powerpins, 4V. It doesn't look like there is something wrong with the IC.I am starting to think that this might be a firmware issue.Pin 2 might be an enable pin and it has zero volts. Hmm.

author: wasedadoc
author_rank: Super Contributor
timestamp: January 22, 2024, 04:35:46 pm
content: Enables can be active low. That is the case with the chip I linked to.

author: hgg
author_rank: Frequent Contributor
timestamp: January 22, 2024, 04:38:44 pm
content: Indeed, but this is a different IC. I should measure this pin with audioenabled and disabled to see what's going on.

author: coromonadalix
author_rank: Super Contributor
timestamp: January 22, 2024, 04:44:42 pm
content: the white connector pins are you sure they are soldered correctly, no broken solder ? even if they seem okay ?

author: hgg
author_rank: Frequent Contributor
timestamp: January 22, 2024, 04:46:21 pm
content: They are, first thing I've checked.Anyway, I am measuring directly at the IC output pins and there is no audio.

author: wasedadoc
author_rank: Super Contributor
timestamp: January 22, 2024, 05:04:31 pm
content: Which pin of the IC has audio going in? I highly doubt it is via the 141k resistor into pin 3.

author: hgg
author_rank: Frequent Contributor
timestamp: January 22, 2024, 05:11:50 pm
content: Exactly the same thought, but that was the only pin thatthe oscilloscope showed a 1V p2p waveform that wassimilar with the music beat as well.

author: hgg
author_rank: Frequent Contributor
timestamp: January 24, 2024, 04:46:38 am
content: I measured again Pin #2 and it has zero voltage with either the Internal speaker selectedor deselected. All pins remain at the same state regardless of whether the Internal speakeris selected or deselected and at the same time you can measure the audio waveform on the1k resistor on the right side. Not sure what's going on. PAM8302A looks like having thesame pinout.