[BUILD] 1176LN Rev D DIY

[patxiplg]

I just wanted to let you know that I decided to switch the two FETs and the problem is exactly the same, so I think it's not a FET problem... Even though I put sockets just in case.

Any ideas guys? Thanks in advance!

 

[Echo North]

I just wanted to let you know that I decided to switch the two FETs and the problem is exactly the same, so I think it's not a FET problem... Even though I put sockets just in case.

Any ideas guys? Thanks in advance!

I know you're not fully calibrated, but what are you voltages agains the schematic with voltages:

http://mnats.net/files/1176REVD_VOLTS.pdf

Particularity in that meter section.  Also you're moving the shorting pin?  Did you match your own FETs?

Thanks,

Mike

 

[mnats]

Could anyone give me some advise or guide me a little bit so I can find the problem, please? I have checked everything and it seems to be OK! Also the soldering was very very clean, it's strange... Maybe you know a way or a technique to test a certain part of the circuit and eliminate possibilities?

Thanks in advance guys!

Check the troubleshooting FAQ linked from the first line of the first post of this thread. Read the section just below the links to the  schematics with the voltages posted. If you have truly checked 'everything' and there is no fault with the circuit...it would work!

 

[robertoray]

Hi,
i Just started this project and i move my questions here, even if i'm working to the stereo version.
I have general grounding questions.

1) if we don't remove the paint through holes the pots will not be connected to the chassis.
- Is it a matter if i leave the pots not grounded? Some experience?

2) Long question:
The shield of XLR are connected to the chassis.
After input transformer balanced/unbalanced, we lost the chassis ground and we use the negative pole of the signal (signal GND) for shielding.
- Why don't use the chassis ground for all shields anyway?
Assuming that the connection from C25 negative pole to the lug of the transformer have to be done.
- Right?
And for the stereo version for both boards.
- Right?
And assuming that is the only point where the signal GND are connected to the chassis GND.
- Right?
- Why exactly we have to connect the signal GND to the chassis GND?
- For shielding with negative pole, as we are doing?
- Or the connection to the chassis ground don't have influence on the signal GND insulation?

That's why i will try to separate the transformers to the chassis for disconnect signal GND and chassis GND, if it's possible.
For me sound strange to connect signal GND directly to the chassis and to earth.
Or, in case, i will try to put a loop breaker.
- But in which way?
I attached two pictures.

By the way, if someone here have experience with stereo link board, i'm in the stereo link discussion with a big dilemma about LOOP input impedance and ext. sidechain correct wiring.
I really apreciate any kind of opinion, if i say something wrong, please correct me.

 

[robertoray]

2nd picture

 

[robertoray]

Could anyone give me some advise or guide me a little bit so I can find the problem, please? I have checked everything and it seems to be OK! Also the soldering was very very clean, it's strange... Maybe you know a way or a technique to test a certain part of the circuit and eliminate possibilities?

Thanks in advance guys!

Check the troubleshooting FAQ linked from the first line of the first post of this thread. Read the section just below the links to the  schematics with the voltages posted. If you have truly checked 'everything' and there is no fault with the circuit...it would work!

I checked ALL the FAQ (the first thing I did..) and none of them is what happens to me or help in any way unfortunately.

And I checked again everything I could and knew how to do it in my compressor: component values, wiring,etc. Also measured the voltages Mike told me and posted them because they are very different from the schematic ones. I searched for this issue online and only found one guy here (I contacted him) and he told me he couldn't solve it and gave up...

What more can I do? I'm very limited in terms of audio electronics understanding.

I'm only asking for ideas of how to locate the problem in the circuit so I can know which parts are not involved.

And it could happen it's perfectly built and wired and it's not working. There's a possibility of having some faulty components!! I read some guy here with bad FETs..

Thanks in advance.

i would like to help you, but i don't yet arrived at this point.
I don't have experience.
But i've a question:
-Are you absolutely shure that the trimmers are soldered in the right direction?
Because if it turned 90° you may have a short circuit in all 3 pins of the trimmer.
- look to 0 set pot if it's connected to the right way too

 

[Echo North]

Could anyone give me some advise or guide me a little bit so I can find the problem, please? I have checked everything and it seems to be OK! Also the soldering was very very clean, it's strange... Maybe you know a way or a technique to test a certain part of the circuit and eliminate possibilities?

Thanks in advance guys!

Check the troubleshooting FAQ linked from the first line of the first post of this thread. Read the section just below the links to the  schematics with the voltages posted. If you have truly checked 'everything' and there is no fault with the circuit...it would work!

I checked ALL the FAQ (the first thing I did..) and none of them is what happens to me or help in any way unfortunately.

And I checked again everything I could and knew how to do it in my compressor: component values, wiring,etc. Also measured the voltages Mike told me and posted them because they are very different from the schematic ones. I searched for this issue online and only found one guy here (I contacted him) and he told me he couldn't solve it and gave up...

What more can I do? I'm very limited in terms of audio electronics understanding.

I'm only asking for ideas of how to locate the problem in the circuit so I can know which parts are not involved.

And it could happen it's perfectly built and wired and it's not working. There's a possibility of having some faulty components!! I read some guy here with bad FETs..

Thanks in advance.

i would like to help you, but i don't yet arrived at this point.
I don't have experience.
But i've a question:
-Are you absolutely shure that the trimmers are soldered in the right direction?
Because if it turned 90° you may have a short circuit in all 3 pins of the trimmer.
- look to 0 set pot if it's connected to the right way too

Sounds like just your meter circuit is acting up.

Did you match Q12 and 13 for HFE?

Try setting the Null and Zero, and tracking trimmers mid way before attempting the calibration.

Confirm your 28/29/7/G wires are securely in the headers (pull on them).  Check that wiring.

Triple check the resistor values in that GR meter section.

Mike

 

[Echo North]

Could anyone give me some advise or guide me a little bit so I can find the problem, please? I have checked everything and it seems to be OK! Also the soldering was very very clean, it's strange... Maybe you know a way or a technique to test a certain part of the circuit and eliminate possibilities?

Thanks in advance guys!

Check the troubleshooting FAQ linked from the first line of the first post of this thread. Read the section just below the links to the  schematics with the voltages posted. If you have truly checked 'everything' and there is no fault with the circuit...it would work!

I checked ALL the FAQ (the first thing I did..) and none of them is what happens to me or help in any way unfortunately.

And I checked again everything I could and knew how to do it in my compressor: component values, wiring,etc. Also measured the voltages Mike told me and posted them because they are very different from the schematic ones. I searched for this issue online and only found one guy here (I contacted him) and he told me he couldn't solve it and gave up...

What more can I do? I'm very limited in terms of audio electronics understanding.

I'm only asking for ideas of how to locate the problem in the circuit so I can know which parts are not involved.

And it could happen it's perfectly built and wired and it's not working. There's a possibility of having some faulty components!! I read some guy here with bad FETs..

Thanks in advance.

i would like to help you, but i don't yet arrived at this point.
I don't have experience.
But i've a question:
-Are you absolutely shure that the trimmers are soldered in the right direction?
Because if it turned 90° you may have a short circuit in all 3 pins of the trimmer.
- look to 0 set pot if it's connected to the right way too

Thanks for your help! But yes, they're connected right... Also my voltage in r74 does change when I turn the trimpot.

You might want to reflow those joints. If you have a decent desoldering tool take it out (the trimmer) and test it as described in the manual. 

Check those resistor values.

 

[Echo North]

Hard to say.  I'm not an expert on that discrete meter section, though I should be as it seems simple enough.  I'd need to poke around and see it in person.  We offer repair on all of our builds if that interests you.  Info is on our site under "Repair".

Other than that it would seem to me that you're unit is working well other than the GR meter circuit.  Keep in mind I can't guarantee the rest of your unit is fine, so don't assume anything, it just seems that way based on your in/out and qbias info.

The GR meter circuit is labeled on the schematic and and PCB.  It wears just consists of wiring from the meter PCB (28 and 29) and the bias voltage (7 and GND), 3 trimers, 3 transistors, and 9-12 resistors depending on what you include.  It's also depending on getting supply from both the +30VDC and -10VDC rail.  So there is not much to troubleshoot.

Checking the supply:
- You should get +30VDC (ref ground)  on one side of R79.  The side NOT connected to Q11.
- You should get -10VDC (ref ground) on one side of R76.  The side NOT connected to R75.

Check all 9 of those resistor values in that square VERY carefully.  Learn how to read the color codes on the resistors:
http://www.digikey.com/en/resources/conversion-calculators/conversion-calculator-resistor-color-code-4-band

Check the continuity between all of the traces in that section to check for cold solder or lifted bad. VERY Important.

Does your meter work in +4/+8 mode with a signal at the input?

Test all three trimmers. 

If all else fails replace Q12/13.  If still failing Replace FETs but I would do this as a last resort.

That is pretty much everything you can check, unless you have a deeper issue.

Mike

 

[mnats]

[quote author=1176 Troubleshooting FAQ]Note that there is a voltage drop of approximately 0.6 V between the base and emitter of the bipolar transistors. Any voltages that are grossly different from the ones that appear in the schematic corresponding to the revision you're working on will point to the problem area.[/quote]

[quote author=patxiplg]
Q12:

E: -0,88 VDC
C: 15,04 VDC
B: -0,81 VDC
[/quote]

The voltage difference between the Base and Emitter for that transistor is 0.07 Volts instead of the ~0.6V indicated. Did you test that transistor and test the surrounding components? What was the result?

 

[Echo North]

The voltage difference between the Base and Emitter for that transistor is 0.07 Volts instead of the ~0.6V indicated.

That's a great catch.

 

[dbonin]

However I must have made another mistake somewhere else... It seems like the "threshold" is so high that I have to crank the input all the way CW to get some compression (working with a decent output preamp signal, around -10dB) . Also the unit is very very noisy (like white noise) and it boosts the input signal even with the input and output at 12 o'clock both, for example, so the output is hotter than the input (even without compressing). The attack and release work fine though.

Check the orientation of C7

 

[dbonin]

Check the orientation of C7

Hey dbonin:

I checked the polarity and it's right. I have checked all the voltages of the compressor now and they all seem to be right (aprox.) but Q14 and Q3 differ a little bit more... According to the schematic I should be getting 12V in the emitter of Q14 and I'm only getting 11,1V. In the collector  of Q3 I'm getting 11,7V and it should be 12,58V. Do you think it's an important difference or indicative of a problem?

Thanks!

Those values are fine. 
Noise can come from a few common sources - namely poor grounding, misplaced caps, wiring (position) and soldering issues.

• Did you check for continuity from the chassis to the metal can of the input transformer? Continuity  all around the case front to back, side to side?
• No wires over the PCB?
• output and release pots are not swapped?
• input transformer is step down - is it positioned correctly?

...just a few things off the top of my head that may cause what you are experiencing. 
I always tell people, start at the beginning  and start tracing the signal - you will eventually find the problem.

 

[dbonin]

patxiplg - if you can, please post a pic of the inside of your case, just so we can get a sense of the wiring that was done.

 

[Echo North]

patxiplg - if you can, please post a pic of the inside of your case, just so we can get a sense of the wiring that was done.

Hey mate!

I checked all the possible problems you mentioned and I think all things are OK (and pots not swapped!).
I'm reading about the 1176 and it seems to be a little bit noisy, I don't know exactly what's acceptable and what not, but mine adds an amount that can be a problem when recording.

The first thing I'd like to solve is the "threshold" issue being too high that I have to crank the Input hard (almost 100%) which makes the noise thing worse of course! I'm feeding the 1176 with a normal level signal coming out of a Warm Audio TB12 pre (around -6dB in my interface if I plug directly from the out of the pre). But that signal isn't "hot" enough for the compressor to start compressing... I have to crank the input to the max!

She shouldn't be loud at all.  Should be dead quiet other than a little hiss if everything is cranked including your monitors.

Threshold is controlled by the DC at pad 21.  It's going to be a negative voltage and controlled by the resistors on the ration PCB.

With no signal what are our DC measurements at 21 for each ratio.

It also works in conjunction with Pad 22.  What are your AC readings there with a 1K 0dB signal with each ratio and controls all in the middle?

Triple check your ratio board R values and wiring. Check your Bias.

Mike

 

[Echo North]

Attack and release wiring and r and c values as well.

 

[patxiplg]

She shouldn't be loud at all.  Should be dead quiet other than a little hiss if everything is cranked including your monitors.

Threshold is controlled by the DC at pad 21.  It's going to be a negative voltage and controlled by the resistors on the ration PCB.

With no signal what are our DC measurements at 21 for each ratio.

It also works in conjunction with Pad 22.  What are your AC readings there with a 1K 0dB signal with each ratio and controls all in the middle?

Triple check your ratio board R values and wiring. Check your Bias.

Mike

Hi Mike:

DC in pad 21, no signal, all parameters in the middle:

4:1: -1,47VDC
8:1: -2,43VDC
12:1:-3,58VDC
20:1:-6,64VDC

AC in pad 22, 0dB 1kHz input signal, all parameters in the middle:

4:1:0,064VAC
8:1:0,137VAC
12:1:0,225VAC
20:1:0,465VAC

Are the voltages right?

I checked all the things and didn't find anything wrong... I re-calibrated again the unit following mnats method and again even I could do it perfectly it's not working well.

As I mentioned before, in addition to the white noise problem, there's a big boost in the signal which I think shouldn't be there. I mean with the attack in OFF, 1kHz 0dB input signal and the input and output knobs at 12 o'clock it should be close to unity gain, right? Well, I'm getting 0,775VAC in the input and 4,153VAC in the output! So if I push the +4 or +8 buttons the needle slams to the right. I don't know why is that big boost happening with both input&output at 50%!

I checked the pot and it's the correct value for release and output, so I didn't swap them. What more could this problem be caused by? Maybe when solved this one, the other one of the distortion won't happen anymore!

 

[Echo North]

Seems ok.  What is your AC with signal on the - side of C19?  All ratios.

 

[patxiplg]

Seems ok.  What is your AC with signal on the - side of C19?  All ratios.

Hello Mike:

From ground to - of C19, all parameters in the middle:
4:1: 0,56VAC
8:1: 1,22VAC
12:1: 2,02VAC
20:1: 4,16VAC

About the boost issue, don't you think it's clearly something wrong?

Thanks!

 

[dbonin]

Seems ok.  What is your AC with signal on the - side of C19?  All ratios.

Hello Mike:

From ground to - of C19, all parameters in the middle:
4:1: 0,56VAC
8:1: 1,22VAC
12:1: 2,02VAC
20:1: 4,16VAC

About the boost issue, don't you think it's clearly something wrong?

Thanks!

Just for grins, try this "output" test:
http://groupdiy.com/index.php?topic=20058.msg740305#msg740305

Your ratios are changing in the right direction with respect to 4:1 = least VAC = most compression on up to 20:1=MOST VAC= LEAST compression, but the RANGE of values (from smallest to largest) seems to be way off.  I could be wrong as I don't have an 1176 in front of me...  (Mike has sent me another so I will check soon  )