Too low (and decreasing) voltage when testing U24

Hello,

Sorry for any noob-ness that might follow, but I really hope you guys can help me…

I’m currently testing U24 before soldering in the IC, inspired from the Yocto1 build manual: http://www.e-licktronic.com/en/content/36-noise). I’m getting -15 V over green dot to TP4 at U24 in the noise section. But the red dot starts at ~12 V and keeps slowly decreasing … This is somewhat more than the 5% error margin, so there must be something wrong… Right??

For TM4 I could not find the 22K Ohm B type trimpot in the mouser BOM which I bought, but found a 25K Ohm (lin/log not specified) which fits with the Yocto1 build (http://www.e-licktronic.com/en/content/36-noise), so I used that.

More details:

I followed the Yocto v2.0 assembly guide PDF, which means I:

1. Soldered the PSU part on the I/O board.
2. Soldered the rest of the I/O board.
3. Soldered the sequencer (but only the highlighted parts)

I have not yet put the ATMEGA into its socket.

Then, according to the guide, I should be ready to build the individual voices. So I built the noise section first, and did the testing as specified above. I then later realised that, for the yocto 1, the main board components for the PSU should already be soldered on before continuing to the voices.

Did I break anything by not doing this? It seems like I’m not the only one who fell into the trap about not finishing the main board power (see viewtopic.php?f=27&t=1427), but I finished the rest of the PSU on the main board too, still the same.

Should I connect more than just the power cable (I/O J8 -> Main unmarked in cowbell section)?

Thanks in advance.

I’m having the same problem. What do I need to add to finish the main board PSu please?

Sorry didn't see this before now.. I simply didn't get the ground from the correct reference... Very silly. Did you fix your problem?

Vincent also suggested to check if I had soldered R237 and R236, which I had. And if C79 and C80 was the right way. Don't know if that helps.. Good luck!

Oenone wrote:
For TM4 I could not find the 22K Ohm B type trimpot in the mouser BOM which I bought, but found a 25K Ohm (lin/log not specified) which fits with the Yocto1 build (http://www.e-licktronic.com/en/content/36-noise), so I used that.

I see you solved this, but I checked this against the table I made and I agree that the 25K pot in the BOM looks like it is supposed to be TM4 which is listed as 22K in the parts list

dnsmth9000 wrote:
Oenone wrote:
For TM4 I could not find the 22K Ohm B type trimpot in the mouser BOM which I bought, but found a 25K Ohm (lin/log not specified) which fits with the Yocto1 build (http://www.e-licktronic.com/en/content/36-noise), so I used that.
I see you solved this, but I checked this against the table I made and I agree that the 25K pot in the BOM looks like it is supposed to be TM4 which is listed as 22K in the parts list

Yes, this was also confirmed to be ok by Vincent.

Oenone wrote:Sorry didn't see this before now.. I simply didn't get the ground from the correct reference... Very silly. Did you fix your problem?

Vincent also suggested to check if I had soldered R237 and R236, which I had. And if C79 and C80 was the right way. Don't know if that helps.. Good luck!

Hi, thanks for your reply. Do you mind explaining to me what you mean by not getting the ground from the correct reference? R237 and R236 are soldered and C79 and C80 are the right way. Thanks!

Ed_Mc wrote:
Oenone wrote:Sorry didn't see this before now.. I simply didn't get the ground from the correct reference... Very silly. Did you fix your problem?

Vincent also suggested to check if I had soldered R237 and R236, which I had. And if C79 and C80 was the right way. Don't know if that helps.. Good luck!
Hi, thanks for your reply. Do you mind explaining to me what you mean by not getting the ground from the correct reference? R237 and R236 are soldered and C79 and C80 are the right way. Thanks!

I stupidly used one of the test points. When i used GND on the PSU (J8), everytthing was fine.

Thanks for getting back to me so quickly. I was doing the same thing wrong

Cheers for the help!

Ed

Ed_Mc wrote:Thanks for getting back to me so quickly. I was doing the same thing wrong

Cheers for the help!

Ed

Heyy no problem, and good luck going forward! We'll get through this eventually