# Roboto - no sound when engaged



## ChunkyKarma (Jun 18, 2020)

My first PedalPCB project - I actually made two of these and both do not pass audio when engaged. Hopefully another pair of eyes can see if I did something incorrectly. 
      I didn't have sockets for an 18 pin IC so I soldered it directly to the board. Maybe the two HT8950s are  bad? They were a bit tricky to find. I ended up getting them from this ebay seller who seemed to have a good rating:








						5PCS Audio Amplifier IC HOLTEK DIP-18 HT8950  | eBay
					

Find many great new & used options and get the best deals for 5PCS Audio Amplifier IC HOLTEK DIP-18 HT8950 at the best online prices at eBay! Free shipping for many products!



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How would I go about testing the HT8950?
Here are some pics. I would me happy to share the decal I made if anyone wants me to sent it their way.
Thanks!
Greg


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## Mcknib (Jun 18, 2020)

At a quick glance

Possibly your DC jack shorting on the bare metal of the enclosure is the DC jack all plastic? it's hard to tell if that's metal, do you get 9v to the pcb

or from the ppcb wiki might be your tip connection


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## Vildhjuggah (Jun 18, 2020)

quite a few spots that could use some more solder it seems, at least from the visible side


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## ChunkyKarma (Jun 19, 2020)

Thanks for the replies. I will check those.


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## ChunkyKarma (Jun 19, 2020)

Mcknib said:


> At a quick glance
> 
> Possibly your DC jack shorting on the bare metal of the enclosure is the DC jack all plastic? it's hard to tell if that's metal, do you get 9v to the pcb
> 
> ...


It's a metal enclosure. Bypass works fine and the issue was the same when I took everything out of the enclosure. The jack I have in it is just like in your picture: ground to "sleeve" -  in and out from the footswitch to "tip".


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## Robert (Jun 19, 2020)

Does the LED light when the pedal is active?    If so you can eliminate the DC jack as the problem.

First make sure you have 3.3V on pin 7 of the HT8950.

If you have an audio probe check for audio on pins 6 and 9 of the HT8950 IC.   If you have audio on pin 6 but not pin 9 I would suspect the HT8950.

I don't recall any cases of those being fakes so far, but they _are_ getting rare so it's bound to happen.


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## ChunkyKarma (Jun 19, 2020)

The LED does light up when engaged. I will check the measurements on those pins. Thanks for the help!


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## ChunkyKarma (Jul 11, 2020)

So I finally had a chance to check out everything suggested - zero voltage on pin 7 and no audio on pin 6 or 9 of the HT8950. Nothing on any pin for that matter. Should I get out my solder sucker and recite the mantra "I will never install another IC without a socket" 100 times or is there something else I should check?


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## Mcknib (Jul 11, 2020)

If you haven't already I'd trace the 3.3v supply back before you decide the chips trashed make sure it's getting voltage to it

Check your L78L33 is putting out the correct voltage and check all the 3.3v points on the schematic 

Either you're extremely unlucky with dry joints or it's the same thing with both builds hopefully two cheap dodgy regulators rather than the chips  

The values I can see etc look correct


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## zgrav (Jul 11, 2020)

no audio on pin 6 suggests you need to use your audio probe to see where your audio stops.  do you have audio on pin 1 of IC1?   In you do not, do you have audio on IC1 pin 2?    If audio is not getting out of IC1, check the power and grounds for that IC.  If you have audio on IC1 pin 1,  follow the schematic for the path between IC1 pin 1 and pin 6 on the HT8950.


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## ChunkyKarma (Jul 11, 2020)

Thanks for all the tips. I will check everything that's been suggested.


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