Audio Amp board, not working, stuck - Page 1
Forum section: electronics / beginners

author: aaronhance
author_rank: Regular Contributor
timestamp: February 26, 2025, 08:25:06 pm
content: Hello, I've designed a board, mostly the same as the reference schematic(tpa3118d2). I had it made, It has no audio output. I have measured the following things, and probably more I can't remember. 3V in+ bias to gnd, and its present at 2.98v, mute is low, fault is high (no issue), output of amp is 6v same for bootstrap and speaker output pads(at 12v power). I can't find any shorts, tried input voltage from 11v to 16v. audio source works with cheap amp board I got from amazon. I compared my schematic to the reference and others I found, only small differences, mostly in output filtering and power filtering. Things from the amp seem to be as expected, except obviously the output, which I have hooked up to 4 ohm speakers via a crossover. Audio source is a PCM5102. I'm not really sure what to test next. Any ideas would be helpful. Thanks.

author: SuzyC
author_rank: Frequent Contributor
timestamp: February 26, 2025, 09:58:11 pm
content: I cannot visually determine the match of your PCB to your schematic and the reference schematic.What could possibly go wrong?1) PCB layout error.2) Missing component on PCB.3) Wrong component placed on PCD, i.e. a cap where there should be a resistor..etc.4)Wrong resistor value error on PCB.5)Solder bridge.If you have a scope, verify audio test signal is present on the IC input pins.Obviously, there is a difference between the reference schematic and your fabricated PCB causing fault.I would guess the problem is most likely not a failure of the IC itself.

author: jwet
author_rank: Frequent Contributor
timestamp: February 27, 2025, 04:23:35 pm
content: The only thing that I see that could be an issue is that the DS shows pull up on Mute and DZ, etc and you have pull downs of a high value. If you look at the data sheet, they have this spec for Iin for the logic in of 50 uA (for a high)- there is obviously something behind these pins like a level shifter. If you have 50 uA currents and 100k pull downs, you'll drop 5v, game over. Oddly the mode sel pin doesn't show up on the big block- it shows it internally. The mute and SDZ are shown going through a TTL converter. TTL input sort of implies that you have to sink current for a low- a bit ambiguous.My recommendation would be to remove the 100K on mode sel and tie this to ground as shown in the standard schematic. Remove the pull downs from the Mute and make this a pull up. This is could all be nothing but it does look odd.Good Luck

author: aaronhance
author_rank: Regular Contributor
timestamp: March 01, 2025, 01:28:58 pm
content: I removed the resistor of mode select and bridged it. The DS and various other schematics show 100k pull down on mute an no other connections, they also show a working amp. The SDZ pull up at 100k, I measured the voltage 13v ish when running at 15v ish. That's above the required 2v. I did try a 10k pullup on mute, nothing still. I also tried the other output channel.I also checked all of the components, resistors are where resistors are supposed to be their values are correct.Voltage speaker out is 6v, bootstrap 6.67v, there is no analogue waveform at all, just tiny bit of noise. Audio in, I have to bridge the ground of the incoming audio to the amp gnd, then I can see it. Still nothing out. I've attached image of speaker out readings.I've looked at many different schematics the ds one, the reference one, and others, I just can't figure out any difference that would stop me from getting any output. Maybe that's just my ignorance(probably).https://hackaday.io/project/186117-i-made-my-own-class-d-amplifier/detailshttps://www.ti.com/lit/df/tidrd32/tidrd32.pdf?ts=1740813462709

author: aaronhance
author_rank: Regular Contributor
timestamp: March 01, 2025, 02:53:01 pm
content: oh bloody hell my gain select divider is not connected to ground the vias was on the wrong net. I got a pop on my speaker now, just hope I didn't damage the chip in my testing.

author: jwet
author_rank: Frequent Contributor
timestamp: March 01, 2025, 02:54:28 pm
content: Are you running now?! Bravo.

author: aaronhance
author_rank: Regular Contributor
timestamp: March 01, 2025, 03:08:34 pm
content: not yet, but progress, I now get a speaker pop when turning on. Weird stuff If I touch my oscilloscope probe to the output, only before the output filter, I get noise on my speaker, I guess it amplifies noise from my scope/leads? So that would indicate an audio source issue?

author: aaronhance
author_rank: Regular Contributor
timestamp: March 01, 2025, 03:11:58 pm
content: I got it grounding my source gnd to amp ground I get some audio, but it is quite noisy, maybe soldering these wires will help. WOOP woop.

author: aaronhance
author_rank: Regular Contributor
timestamp: March 01, 2025, 03:32:13 pm
content: it hisses on start-up but, I get good audio.

author: jwet
author_rank: Frequent Contributor
timestamp: March 01, 2025, 03:50:35 pm
content: Congratulations! I know that feeling when you crack something that has stumped you. Carry on.