Sound Skulptor forums

Build help and troubleshooting => LA502 Optical Compressor => Topic started by: Théo S on February 08, 2022, 03:36:16 PM

Title: Meter LEDs -12, -16, -20 are not lightning
Post by: Théo S on February 08, 2022, 03:36:16 PM

Hi everyone.

I've just finished the assembly of this LA502 module and i'm now onto the calibration and setup step.

Power voltage seems fine, i'm getting +/-15,95 VDC. Compressor Check seems to be fine too, Gain and Peak pots seems to work as expected.

When I'm calibrating the Meter,  I can get the -3 / -6 and -9 LEDs lightning without any trouble while adjusting P4 / P5 and P6 trimmers at 10,6 / 7,5 and 5,3 VAC signals on output. But I can't get -12 / -16 and -20 LEDs ligntning at 3,72 / 2,4 and 1,5 VAC output.
On the other hand,  when I'm switching on "6" on the ratio switch and turning the Peak pot, these LEDs are lightning all 3 at the same time when reaching 0,60 VAC output. Same thing with a "20/limiter" ratio when reaching 0,56 VAC. P7/P8 and P9 don't seems to have any effect on the lightning (or not) of their respective LEDs.

I've already checked my solder joints and reflowed a couple of suspicious joints, but nothing changed. 
Any ideas ?

Thanks!
Théo

Title: Re: Meter LEDs -12, -16, -20 are not lightning
Post by: JPK on February 09, 2022, 11:24:51 AM

Check value and solder joints of R36, R37, U7, P7, P8, P9, U9.

Title: Re: Meter LEDs -12, -16, -20 are not lightning
Post by: Théo S on February 10, 2022, 02:32:48 PM

Hi JPK, thank you for your answer.

I went over my joints, with a special care for those you mentionned, but for now situation is just the same, nothing changed.
Is there a particular value that I should check to have more information of the issue?

Thanks for your help ! 

Théo

Title: Re: Meter LEDs -12, -16, -20 are not lightning
Post by: JPK on February 10, 2022, 03:39:44 PM

What are the DC voltages you get on both sides of R37, against 0V.

Title: Re: Meter LEDs -12, -16, -20 are not lightning
Post by: Théo S on February 10, 2022, 04:42:24 PM

2,47 VDC on both sides.

Title: Re: Meter LEDs -12, -16, -20 are not lightning
Post by: Théo S on February 10, 2022, 04:45:15 PM

And for R36: 15,92 V on Left side / 2,47V on right side.

Title: Re: Meter LEDs -12, -16, -20 are not lightning
Post by: JPK on February 10, 2022, 06:20:34 PM

All good.
Check that you didn't reverse one of the LED's. You can do this with the DMM in diode position, it will light up the LED when connected in the right direction.
Check that there is continuity between U8 pins 5, 7, 9 and U9 pins 5, 7, 9.

Title: Re: Meter LEDs -12, -16, -20 are not lightning
Post by: Théo S on February 11, 2022, 10:58:27 AM

So, everything is ok.
Leds are all in the good position, and there is continuity between pins 5,7 and 9 of U8 and U9 (continuity on each others on the same IC and between both ICs).

Title: Re: Meter LEDs -12, -16, -20 are not lightning
Post by: JPK on February 11, 2022, 11:41:24 AM

Try swapping U8 and U9 to see if the issue moves to the 3 other LED's.

Title: Re: Meter LEDs -12, -16, -20 are not lightning
Post by: Théo S on February 11, 2022, 12:05:04 PM

Yes I've tried it, but it don't. The problem le still on the same LEDs.

Title: Re: Meter LEDs -12, -16, -20 are not lightning
Post by: Théo S on February 11, 2022, 04:22:45 PM

Maybe an issue with the connector CN1?

Title: Re: Meter LEDs -12, -16, -20 are not lightning
Post by: JPK on February 12, 2022, 10:00:12 AM

You can verify the CN1a/b connector with your ohmmeter by checking the continuity from the bottom pads on the main PCB to the top pads on the LED's PCB.

Title: Re: Meter LEDs -12, -16, -20 are not lightning
Post by: Théo S on February 14, 2022, 11:53:54 AM

Continuity check between pads on Cn1a & Cn1b look good, and it seems that there is no short cuts between neighbour pads, which I can confirm visualy.

However, I noticed that when I put my DMM probes on : (I am counting from the top of the connector, where there is the round mark on the pcb) 
- Cn1a 1rst pad + Cn1b 8th pad : -20 LED is lightning
- Cn1a 2nd pad + Cn1b 1rst pad : -3 LED is  lightning.
-    "            "         + Cn1b 8th pad : -20 LED is lightning.
- Cn1a 3rd pad + Cn1b 1rst pad: -3 LED starts lightning a bit.
-    "           "         + Cn1b 8th probe : -20 LED is lightning.
- Cn1a 4th pad + Cn1b 3rd pad : -9 LED is lightning.
-    "          "          + Cn1b 8th pad : -20 LED is lightning.
- Cn1a 5th pad + Cn1b 3rd pad : -9 LED is lightning.
-    "          "          + Cn1b 8th pad : -20 LED is lightning.
- Cn1a 6th pad + Cn1b 8th pad : -20 LED is lightning.
- Cn1a 7th pad + Cn1b 4th or 5th pad : -12 LED is lightning.
-    "          "          +  Cn1b 8th pad : -20 LED is lightning.
- Cn1a 8th pad + Cn1b 7th pad : -16 LED is lightning.
- Cn1a 9th pad + Cn1b 8th pad : -20 LED is lightning.

It also seems to exist a signal continuity between Cn1a 9th pad & Cn1b 7th pad.

Is there something wrong with all of that?

Title: Re: Meter LEDs -12, -16, -20 are not lightning
Post by: JPK on February 15, 2022, 03:37:32 PM

It also seems to exist a signal continuity between Cn1a 9th pad & Cn1b 7th pad.
Is this true when the connectors are disconnected? There should only be a connection between 6&9 on CN1a and 4&5 on CN1b.

Title: Re: Meter LEDs -12, -16, -20 are not lightning
Post by: Théo S on February 17, 2022, 11:44:48 AM

Yes,  actually when the connectors are disconnected there is only a continuity between Cn1a 6&9 and Cn1b 4&5. And when they are connected there is also a continuity between Cn1a 9 & Cn1b 7.

Title: Re: Meter LEDs -12, -16, -20 are not lightning
Post by: JPK on February 18, 2022, 04:03:24 PM

And when they are connected there is also a continuity between Cn1a 9 & Cn1b 7
I am not sure I understand.
Are you saying you also have a continuity between pins 7 & 9 on Cn1a (or Cn1b), when connected?