Shruthi low volume

This is my first major electronics build and feel I’ve done pretty well so far. Everything works as it should apart from the very low volume from the audio out. I’ve done a search on the forum which threw up a few answers, firstly I need to check the audio connections throughout the board, but to be honest I’m not 100% what I’m doing. I only have a multimeter to test with too. The R2 bridge is connected. Would it likely be something on the control or SMR4 board?

Any help will be appreciated.

It is probably a soldering issue on the filter board. The only digital value that controls the volume is MIDI CC #7. That is the digital volume control, and it is fully open by default.
Make sure that your mixer isn’t turned down. The Shruthi audio out is very loud so you should never directly plug headphones into it.

If I had to guess, it would be that you accidentally missed a solder point on an IC, have a dry solder joint, or you have accidentally put a resistor in the wrong place.

Photos of your control board please!

Thanks for the replies. I will post photos tonight and will also check the solder joints.

Attached are photos of the control board and filter board. Have not investigated any further, but will do so tonight.

Just trying to ‘probe’ the filter board with an audio lead with the jack removed as per in the SMR-4 troubleshooting, but do I need to have the control board attached. If so then I cannot access the points to probe. Otherwise I’m getting nothing from the filter board itself.

I believe you need to connect two boards together.

To access to points; you can connect two boards with jumper wires ( see picture below ) like once @pichenettes recommended to me

Thanks. I’ll see if I can pick up some jumper wires today.

I’ve just picked up some jumper wires and have a portable scope coming today (not sure how good it will be, but better than nothing).

Ok, I’ve got hold of a cheap portable scope and tried some testing. Not really sure how to read it properly, but it does give a good signal at test point 1, the at test point 2 the signal drops considerably so I’m guessing it’s around here where the problem is. I’ve tried to resolder the IC socket (TL072P) and R14, 15, but haven’t managed to remove them. Could the TL072P IC be damaged?

Have you done the voltage test? Maybe the TL072 doesn’t work at all because it’s not receiving a -5V supply voltage?

The voltage test is all ok on the whole board.

Success. I kept going around the suspect components to resolder them and now I have a beautiful sound coming from my Shruthi. Thanks for your help.