Access-312 Build Thread

[3nity]

As tu construit le op-amp ou deja assemblé?
check tes pads, le pcb est dual side, si le canne de ton transformateur d'entrée touche a un pad c'est un short a terre.
Commence par ca!

Salut.

 

[Guitaratomxbest]

J'ai construit le opamp. C'est un Gar2520 de classicapi. Is there a way to test it alone?

je vais vérifier mes pads sur le pcb pour m'assurer qu'il n'y a pas de short.

Merci!

 

[3nity]

verifie tes composantes ou le transformateur d'entre surtout.
Ou est tu au quebec? a Montreal?
Je peux te preter un SMD2520 qui fonctionne si jamais le tout semble correct.

 

[kml23956]

So my DOA works and I get output but my pot does not changes the volume. I can even cut the leads to the pot and I still have great sounding output but no gain control. Any ideas?

 

[3nity]

make sure you dont have any short.

 

[kml23956]

Thanks but where? The pre works but the volume knob does not.

 

[Guitaratomxbest]

Here's some pics of my built. Let me know if you see anything wrong.
Checked all my component and my input transformer and could not find any short.

I still need to clean all my solder at the back of the board. Maybe the problem is there.

Thanks for your help!

 

[Guitaratomxbest]

Potentiometer and the opamp!

 

[kml23956]

I believe that my problem is in the feedback circuit something in the R4: 100R and R5: 10K or C6 -C7. I have a 10k rev log pot for the gain. C7 is the 100pf/50V. What should C6 be?

 

[kml23956]

Is it just me or is there still rosin on the back of these boards? Did you wash your boards with alcohol? If you did not do that, use a tooth brush and alcohol to clean the backs of these boards.

 

[Guitaratomxbest]

yes you're right. I did not wash the boards. Like I said, i'm really a noob at building electronics.
I need to clean them and test it again, maybe my problem is there.

thanks!

 

[kml23956]

No problem. Now I just need to figure out my problem. 8)

 

[3nity]

guitarxtombest.

your pot wiper  (middle) should be connected to the side with the orange wire,
Try that and let me know.

 

[Guitaratomxbest]

The pot is working great like this... I tried bypass the pot and I had the same problem so it's not coming from there.
I will try to test the DOA soon and if he is not the problem I try to look deeper on the board.

Maybe there is too much gain?? I'm using a EA2622 for input transformer and EA2503 as output. I used all the value of the BOM for every component..
Could it has something to do with the ratio jumper?? (just asking) I jumped 2 and 3 together.

thanks!

 

[3nity]

Can you confirm the values for R4-R5?
Thanks.

 

[kml23956]

Who are you asking?

 

[Guitaratomxbest]

I have 100R on R4 and 10K on R5 for a 10k pot, like said on the BOM.

 

[Guitaratomxbest]

My opamps are working perfectly! So the problem is somewhere else...

 

[3nity]

Hello guys.
Just wanted to tell you all that PCBs for Access-312 boards will be available from now on exclusively from Dan @ collective cases.
He is the man behind a nice collection of cases including the Access-312 case.

Hope you all rush to get new pcbs.

Thanks for your help.

 

[Guitaratomxbest]

Hi guys!

I have a few questions.
I just realised I don't know where the RC resistor goes... There's nothing on the board and the schematic but there is one on the BOM.

Is it normal that I still have some audio passing even when the pot is disconnected?

I still have the some trouble with the pot.. I have a clean 22db of gain with the 2 transformers.. And when i add the potentiometers i can add about 12-13db and after this point i completly loose the signal and only have noise. And everything seems find on the board, and the opamp seems fine when i test it.

Anybody have an idea of why??

Thanks!