Aion Lab Series- No audio

[shawnee]

Hello everyone, I finally finished the Lab Series Preamp project and guess what? I doesn't work!
On the power supply I get always get -15v but +15 is intermittent (I get -0.8v). When I don't get +15v I can remove a random IC or two and power it up and it comes back to +15v. I replaced the voltage regulator but that didn't change the problem. When I do get the +15v with all IC installed all LEDs light up correctly when switching channels and in bypass mode (although the compressor LED is always on and will not go out by turning the pot or the trimmer). I can crank the volume all the way up on either channel and get the slightest bit of volume to be able to hear that all of the pots and switches work on both channels. The master volume control does nothing.

I am going to pull out the schematic and start tracing. Maybe try an audio probe as well. Any ideas on where you would start would be helpful.

[blearyeyes]

Hello everyone, I finally finished the Lab Series Preamp project and guess what? I doesn't work!
On the power supply I get always get -15v but +15 is intermittent (I get -0.8v). When I don't get +15v I can remove a random IC or two and power it up and it comes back to +15v. I replaced the voltage regulator but that didn't change the problem. When I do get the +15v with all IC installed all LEDs light up correctly when switching channels and in bypass mode (although the compressor LED is always on and will not go out by turning the pot or the trimmer). I can crank the volume all the way up on either channel and get the slightest bit of volume to be able to hear that all of the pots and switches work on both channels. The master volume control does nothing.

I am going to pull out the schematic and start tracing. Maybe try an audio probe as well. Any ideas on where you would start would be helpful.

Is this the Madbean Projects Tech Support Page? I can't tell so easy with this Tapatalk app.  Still getting used to it. Did you buy the faceplate with that preamp thingy?

Sounds like you have several issues that need to be tracked down.

[shawnee]

Yes this is the tech support forum.
Yes I am using the Aion Lab Series pcb and enclosure.

[shawnee]

I took some voltages on all of the chips while I had good +15 and -15 power supply voltages. Almost every chip shows 0 volts on all of the pins except for the +15 volt supply on pin 8 (pin 7 on the single op amps) and -15 volts on pin 4. What the heck?

[midwayfair]

I took some voltages on all of the chips while I had good +15 and -15 power supply voltages. Almost every chip shows 0 volts on all of the pins except for the +15 volt supply on pin 8 (pin 7 on the single op amps) and -15 volts on pin 4. What the heck?

It's a split rail power supply. What's halfway between -15v and +15v?

[shawnee]

Yeah I get that but how can every pin except supply voltages be zero?

[midwayfair]

Yeah I get that but how can every pin except supply voltages be zero?

... because 0 is halfway between -15 and 15 ...

[m-Kresol]

Yeah I get that but how can every pin except supply voltages be zero?

... because 0 is halfway between -15 and 15 ...

I'll elaborate on that. The other pins are likely signal lines, ie. AC signal. Since you're measuring DC you'll get a reading of 0.

to enable us to help you properly, please stick to the tech guidelines outlined here: http://www.madbeanpedals.com/forum/index.php?topic=902.0
Post pictures and voltages and we'll try to get you in the right direction

[shawnee]

Thank you for the replies- I get it now Jon thanks to m-Kesol's post. Dang AC, DC, and signal get me confused every time.

I did some poking around with an audio probe and everything seems good until I get to the Master volume/Compressor/Output stages (IC1 - IC9 I get clean audio in and out). When I get to IC10 (CA3080) I get terrible super loud crackling audio. I tried another chip and that didn't do it. I checked the solder joints on the socket with a magnifying glass and everything is shiny and there are no shorts. Here are the DC voltages on the CA3080's:
IC10:
1. 12.91
2. 0
3. 0
4. -14.87
5. 13.53
6. 14.12
7. 15.07
8. 12.86

IC11
1. 0
2. 0
3. 0
4. -14.87
5. -0.9
6. -0.3
7. 15.06
8. 13.15

Here is the page with the documentation:      https://aionelectronics.com/project/l5-preamp/   Any insight would be greatly appreciated.

[blearyeyes]

It took me awhile to figure out that "signal" is considered AC. It fluctuates up and down.  We live with AC in our house Electrical which fluctuates up and down as well. But not all AC is in your wall sockets.

[m-Kresol]

Looking at IC10 on the schematic pins 1 and 8 are not connected, it seems odd to me that you'd measure 12V there.
I'm not sure about pin 5. Recheck all the parts values of the components in the area: R60, R6, R99, R74, R70, R72... there could be something odd there. Also, reflow the solder joints of the IC.

Give us some pics of the front and back of your board and maybe a magnified image of region of IC10 (solder side). We might be able to spot something.

[shawnee]

Thanks again for the help-m-Kresol.
I thought that was strange too that there is voltage on pins that should be no connection. I had to pull the master volume pot to get to the underside of the board but I didn't find any problems anywhere. All resistor values are correct on the ones you mentioned and there are no shorts between pins on IC10. I used the audio probe and pin 2 has clean audio in and pin 6 out is distorted. I wonder if I got a couple of bad CA3080's? That would also explain why the compressor LED is always on and will not go out no matter where I set the compressor pot or trim pot.

[blearyeyes]

Did you ever get this figured out?

[shawnee]

I ordered a couple of metal can CA3080's that came in today. I tried them and I am getting audio from the master volume section and the compressor seems to be working correctly now. The cheapo chinese $2 CA3080's were definately a problem. There are still some issues though. It doesn't seem to have the gain that it should and there is still a weird power supply issue.

[blearyeyes]

Good luck on your quest. At least you have audio now.