Audio Output Problem

I have constructed the Shruthi, but am not getting any sound from the output. I read the troubleshooting page, and constructed the audio probe described (ground to sheath and probe to tip, sent to my sound card). The attached image shows the results of that testing. I can hear the sound at the two points colored green, but for some reason I am not getting any signal after the 100k resistor. It’s strange, that I can hear the signal when I probe on the “upstream” end of the resistor, but hear nothing when probing the other end of the resistor (see picture). When I test this resistor with the meter, I detect the proper 100k Ohms. Any advice will be greatly appreciated.

Just to be clear, the actual image is not my board (I pulled it from the MI page). All components are installed on my actual board. Also, I’ve attached an updated image, showing that proper signal is heard at both points of the C21.

You should only hear signal at one end of the resistor, as the other goes into a current summing node held at 0V by feedback. Is there any signal at pin 1 of IC2? After that check you get sound at pins 1, 8, 7 and 14 of IC7, and pins 1 and 3 of JP3.

@mediocrates sorry if this is a cheeky question, but did you remember to add the jumpers at R1 and R2 (assuming an SMR-4 Mk.2 filter)? I only ask because I forgot to do that with my first Shruthi-1 build, and was similarly puzzled at getting no sound from the output.

Also, check all socketed chips for correct orientation, if you haven’t already done so.

a|x

toneburst, I laughed at that one. I did that on both Shruthis I built!

There is no signal at pin 1 of IC2. Does this suggest that IC2 is broken?

Also, the jumpers are in place.

Thanks to everyone for the help!

Anthony

Do you have a jumper on the 2/4 pole header?

I have the red jumper set to 4 pole

If you don’t get signal at pin 1 of IC2, check that all pins of the IC2 socket are correctly soldered (in particular, the grounded ones). Check the voltages on pin 4 (must be -5V) and pin 8 (must be +5V).

I’m measuring 4.2V on pin 8 but 0V on pin 4…

Please check the power supply section

TL1054 was in backward! Thanks, everyone.

Anthony

Hey, thanks for this thread…had the exact same problem. Something to do with the TL 1054 being the only chip with upside down text which got me confused.