[BUILD] 1176LN Rev D DIY

[Sillen]

the orientation (left to right/right to left) doesn't really matter.
What matters is that you don't use the extra wiper points. THese are the ones that go vertically through the round drawing. if you test them with a DMM, you'll see they check for continuity. Don't use these.

Damn it ....... This really sucks. It is mounted correctly and it is a working trimmer right there now and it still doesn't work. What can be wrong? :/ I'm sending in a 0.773 ac signal actually because I couldn't get it more exactly than that, this shouldn't be much of a problem though right? What else can be wrong?

 

[sr1200]

Are you reading AC or DC?

 

[Sillen]

Are you reading AC or DC?

AC

 

[sr1200]

did you set the Qbias wiper off before you tried to set the input level?

 

[Sillen]

did you set the Qbias wiper off before you tried to set the input level?

i had the wiper set to the middle, 1k ohms on every side from start, the ac from the xlr out doesn't change if i turn the wiper in either direction.

 

[sr1200]

???  set it off, then insert the correct level signal to get the fet into conduction.  If the fet isnt getting there i dont think its going to do anything (maybe someone else can corroborate my potential mis-understanding of how this works)

 

[Sillen]

I turn it off by turning it all the way left I guess?

 

[jplebre]

you turn it "off" by moving the needle up. Then keep going until you reach the end of the trimmer.

 

[Sillen]

you turn it "off" by moving the needle up. Then keep going until you reach the end of the trimmer.

Wut? I was pretty sure this trimmer didn't have an actual end. And by up you mean counter clockwise right ?

 

[sr1200]

theres and end... you may hear a little click every time you twist, thats at the end.

 

[Echo North]

And twist it enough past the end and it will break.

 

[jplebre]

you turn it "off" by moving the needle up. Then keep going until you reach the end of the trimmer.

Wut? I was pretty sure this trimmer didn't have an actual end. And by up you mean counter clockwise right ?

no, the QBias is not related to the meter. However, it puts the fet slightly in conduction (or a lot in conduction) so the signal (and the needle) will drop.
You want to make sure you have offset the Qbias enough so it won't upset your initial setup for the callibration. Turn it so you see the needle go up, then keep turning until you hear the click.

Only then you are safe to set the levels so you get +1vu measurement (assuming VU is set to +4). Then use the Qbias for adjustement so it drops 1dB.
You may have to turn it a few times (because you went to the end of the trimmer). That's ok.

Let us know how you got along

 

[Sillen]

no, the QBias is not related to the meter. However, it puts the fet slightly in conduction (or a lot in conduction) so the signal (and the needle) will drop.
You want to make sure you have offset the Qbias enough so it won't upset your initial setup for the callibration. Turn it so you see the needle go up, then keep turning until you hear the click.

Only then you are safe to set the levels so you get +1vu measurement (assuming VU is set to +4). Then use the Qbias for adjustement so it drops 1dB.
You may have to turn it a few times (because you went to the end of the trimmer). That's ok.

Let us know how you got along
[/quote]

I can't say i'm 100 % sure i actually heard the click from the needle but i turned it like 30 rounds so I doubted it would be any good to turn it more. Same result as earlier this time also, nothing happens when turning the qbias back.

 

[Echo North]

You should have a negative voltage at pad 18.  This is the wiper of your QBias trimmer. Something in the area of 0 to -3V (roughly).

If you don't see a neg voltage here you have a damaged trimmer.  If you do, check for a neg voltage at the FET Q1 gate.  If you don't have the neg voltage there, your attack release is probably wired wrong.

Mike

 

[Sillen]

Ok
The trimmer is ok as expected. I measured it to -3.045 dc. The gate at fet Q1 has positive value though, 0,545 dc. All the wiring from attack pot seems to be accordingly to mnats tutorial, they go to the right places at least. Hmm what should I be looking for more?

 

[Echo North]

Ok
The trimmer is ok as expected. I measured it to -3.045 dc. The gate at fet Q1 has positive value though, 0,545 dc. All the wiring from attack pot seems to be accordingly to mnats tutorial, they go to the right places at least. Hmm what should I be looking for more?

That really weird.  A POS voltage there basically keeps your FET wide open and your compressor in max compression.

Check your cap/diode orientations on your main PCB.

Mike

 

[Sillen]

Yeahh that must be it really! The pcb had no markings on C17 so I just put it in how I thought it should be. Damn... Hate to de-solder stuff.

 

[ln76d]

Yeahh that must be it really! The pcb had no markings on C17 so I just put it in how I thought it should be. Damn... Hate to de-solder stuff.

It has "+" marking on polarization. Even if you phisically don't have this marking, on mnats v2.2 pdf is also marked.
I've used there film capacitor without polarization.

 

[Sillen]

Mine isn't marked for some reason. But yeah it's on the pdf like you said, should've seen it. But now when I looked at it again I realized I was just thinking weird, the polarity was correct after all. :/

 

[ln76d]

Just put the good photo of the top of PCB and all will be clear