[BUILD] 1176LN Rev D DIY

[TheWolfman]

Curiously on my unit it seems like it adds a little ooomph at around 40hz when compressing which is definetly noticable on a kickdrum for example.Just how I like it!

 

[TheWolfman]

I have to say that upon further use of my unit I'm finding it to be rather Noisey.

The noise is based on a 50hz hum,which indicates some kind of grounding issue.I also find the Input pot rather scratchey.

Could this be a ground loop issue?I've connected the balanced input and output leads to each other from the desks insert point and there is no noise,so it isn't a patchbay problem,it is the Rev D itself introducing the noise.It's certainly WAY noiser than any 1176LN I've ever used.

You can see the hum/noise is fairly considerable from the analysis below:

 

[benlindell]

I have to say that upon further use of my unit I'm finding it to be rather Noisey.

The noise is based on a 50hz hum,which indicates some kind of grounding issue.I also find the Input pot rather scratchey.

Could this be a ground loop issue?I've connected the balanced input and output leads to each other from the desks insert point and there is no noise,so it isn't a patchbay problem,it is the Rev D itself introducing the noise.It's certainly WAY noiser than any 1176LN I've ever used.

You can see the hum/noise is fairly considerable from the analysis below:

Have you doubled checked continuity between all the pieces of the case?

 

[TheWolfman]

Yes,Continuity is flawless regarding ground.

 

[rokus666]

One quick noob reply:
while I was soldering the resistors to the board, while I snipped the off the excess wire on the back and there was a little static spark between the snipps and the resistor....
can this damage the components ?

Another question:

Do I have to set the trim pots to a specific value before soldering them to the board?

 

[sr1200]

the pots should be about mid way to make calibration possible(if theyre all maxed or at lowest calibration may not work), but theres no "preset" values. 

 

[rokus666]

the pots should be about mid way to make calibration possible(if theyre all maxed or at lowest calibration may not work), but theres no "preset" values.

Hey Anthony, thanks for the response. I remember on my last build, I have fiddled around the trim posts and the calibration was fine (luckily)

 

[websoul]

Hey all,

Just got a wee issue.  I've spent a couple of days testing and trawling through this thread but I'm still scratching my head a bit with an issue.

It seems to the GR METER DRIVER section has incorrect voltages and I'm not sure why.  Every other area matches up just fine, so it does seem isolated at least.  Audio is getting in and out, but as soon as the GR button is pressed in, nothing happens.  I thought it may have been the resistors, so changed a few of them, but that didn't change anything.  Here are the readings:
Q11 3.18 | 2.57 | 2.90
Q12 1.91 | 1.92 | 2.57
Q13 1.69 | 2.89 | -0.94

Way out!!

I'm wondering if Q11 is bust?  Think it's worth switching with Q1 to check?  I've kind of run out of ideas now.

When the GR button is pressed, the VU moves hard left.  You can hear a very very faint signal if you put you ear close to the board.

Is there anything else I can check?  Tracing the schematic I'm wondering if it's an issue with the board maybe?  Around R72 & R66.  Are these readings correct for these two?

R72 -9.70 | -6.10
R66 -9.70 | 2.57

Thanks in advance.

 

[Echo North]

The gate of Q11 should have a negative voltage.  It's coming from the qbias ref voltage (which should be -0.5 to -1.6VDC) and is connected over by Q11 through pad 7.  Start by figuring out why you don't see a neg voltage there.  Once you get Q1 and Q11 gates with a proper neg bias voltage remeasure everything.

Check all of that wiring that goes to pad 7.

Mike

 

[websoul]

Cheers mike,

I've checked the wiring and all looks good. I wonder if there is an issue with the ratio board or release pot?

 

[Echo North]

Had a look at pad 18 on the schematic.  It's the wiper of the QBias pot.  One of the outside pins on this trimmer goes to ground and the other is tied between to R's that make a voltage divider off the -10 rail.  So basically that wiper is pulling a neg DC from the divider plus some DC from pad 18 off the ratio PCB.  This neg qbias voltage then travels by wire through the attack/release network (see schem) and to pad then to pad 7.

Work your way through that.  What is your VDC at pad 21 with ratio 4 selected?  No signal.

 

[websoul]

Thanks for your help Mike, I feel a bit red faced now.  I had C19 in wrong.  Popped it out and turned it around and bingo, back in action.

I can't believe I missed it!!!  Two days and it was staring right in front of me, ha!

Thanks for your help though

 

[Echo North]

Thanks for your help Mike, I feel a bit red faced now.  I had C19 in wrong.  Popped it out and turned it around and bingo, back in action.

I can't believe I missed it!!!  Two days and it was staring right in front of me, ha!

Thanks for your help though

We've all been there!

8)

 

[TheWolfman]

I was just wondering if anyone has experienced that when the output is set to maximum and the input is increased to about 80% or so that the needle maxes out?

This is without any audio passing by the way.Does this suggest that when the output is driven to a certain point feedback enters the circuit?

 

[Echo North]

I was just wondering if anyone has experienced that when the output is set to maximum and the input is increased to about 80% or so that the needle maxes out?

This is without any audio passing by the way.Does this suggest that when the output is driven to a certain point feedback enters the circuit?

I don't think it's odd to see oscillations with the in/out near max.

 

[Echo North]

I tried to calibrate but when I turn up the input during the adjustment the vu meter won't move up to 0 db as it should. I did ground out pad 22 as it stated in the video. Now any suggestions?

Thanks

Rich

If you have a version with the "off" switch on the attack pot, you can just switch that.  That will ground pad 22.  Feed a 1khz signal into the input at about 0dBu.  You can put your DMM across input xlr pin 2 and 3 and look for 0.775VAC which is about 0dbu.

Now put your DMM across pin 2 and 3 on the output xlr and turn the qbias (in and out knob mid way).  You should see the output moving up or down.  Turn the bias until it gets to the max and doesn't get any higher. 

Then adjust the output knob so you see +11dbu (2.75VAC) at the output.  Now pull the qbias back until you get a 1dbu drop 10dbu (2.45VAC).  That will set you bias.

Mike

 

[RichardM]

Hi,

The readings were right at the input jack but no luck at the output. I could only get a .07 ac reading there. Suggestions?Thanks!

Rich

 

[Echo North]

Hi,

The readings were right at the input jack but no luck at the output. I could only get a .07 ac reading there. Suggestions?Thanks!

Rich

Rotating the bias did nothing?

With the knobs midway what is your reading at the - side of c7?

 

[benlindell]

So I've now replaced the torodial transformer and redid the 2200uf caps, I'm getting a solid +28.5-30V but the -10 rail starts at -3.4ish and decreases slowly. What's going on here?

 

[RichardM]

Reading 10.93 dc at C7