[maos]

I am unable to level match using T1 as discussed in step 7 of the set up guide. The max voltage I am able to attain when the compressor is engaged is 1.13V. Channel 2 level matched without issue.

I have confirmed all ICs are in their correct locations. I have also soaked the two main PCBs in an alcohol bath.

I ran through the troubleshooting voltage tests as described in your other post and these are my results (results in red):

Section 1: All up to spec

Section 2:


Section 3:


Section 4:


Section 5:

Section 6:



Section 7: 



I have ordered some additional trim pots in case the issue is localized to the one on T1.

Thanks in advance for any insight you can provide!

Cheers!

(edited post to add step 7 results)

[JPK]

Your levels are good on TP2 so the issue must be in the output stage.
Check value, direction and solder joints of U7, BR2, RLY1.
If OK, try the other THAT1646 in U7.

[maos]

Thanks JPK! After a reflow of all joints on U7, BR2 and RLY1 I am now able to gain match without issue. 

I really appreciate your help!

[maos]

Apologies, but I may have spoken too soon. Calibration continued without issue until I got to the the balance trim step. When I went to get the channel 1 AC values with 10db of attenuation, I saw that the output level at baseline settings with the compressor engaged was back to the incorrect/low voltage, right around 1.02v. 

I tested on multiple slots, both with and without the extender cable.

Thanks again for your help, it is much appreciated!

[maos]

Ok, I found and solved the issue! After additional testing I noticed that the failure moved from channel 1 to channel 2 and back again. At that point I started thinking there may be an issue with the rack itself. After checking multiple channels I was able to isolate the issue to the cable I was using for the channel 1 input. Swapped out the cable and everything is fine now, across both channels and all slots. 

I am a bit perplexed as how the cable would only cause the drop when the compressor was engaged, but I admit that I am a bit beyond my experience level on the theory side of things. I'd be interested if you have any thoughts on what occurred. 

I am extremely happy with how the build came out and again want to thank you for the support figuring this out! 

[JPK]

I'd be interested if you have any thoughts on what occurred.

Sorry, I can't find an explanation without knowing your setup details.

[peouse]

Hello JP,

Jumping on this thread since I have exactly the same issue. 
Voltage checks are OK, however, I noticed TP2 depends on T1 position, so step6, TP2 is not always 1.5 AC. Right?

I will try the bath this week, in the meantime do you have any suggestions to help me?

Thanks for your help!

[JPK]

I noticed TP2 depends on T1 position, so step6, TP2 is not always 1.5 AC. Right?

TP2 should be at 1.5V AC after T1 has been adjusted.

[peouse]

So the problem I have is that I cannot reach the targeted 2vac while switching on/off the module.
Out+ (while off) = 2vac
Out+ (while on) = From 0.93vac to 1.15vac using the trimmer t1.

Thanks for your help !

[JPK]

So what voltages do you get in the voltages check #6 ?

[peouse]

Hey JP,

For step 6 :
• TP1=1.5VAC / 1.49
• TP2=1.5VAC / 1.71
• TP3=1.5VAC / 1.49
• TP4=0.06VAC / 0.05
• U6 pin1 = 0vdc / 0



Thank you !

[JPK]

Your values are OK.
Are you measuring between pins 2&3 of the XLR (or tip & ring for a jack)?
You should get half of this value between anyone of these pins and ground (0V).
If not, you may have a damaged U7. try swapping with the other set.

[peouse]

That was my mistake... I was using the wrong pin. Measuring from ground...
Now Up and running, thanks a lot for your help