[BUILD] 1176LN Rev D DIY

[dbonin]

I have never heard this before.  was this with out without a test tone passing thru the unit?

Have you searched thru this forum for any of your issues?  Double check your polarized caps - make sure each one is oriented correctly.
Did it always make this sound, since you first turned it on?  Does it happen in bypass mode, with compression turned off?

I can tell you from building a lot of these kits that it's EASY to swap a resistor or place a part backwards - we've all done it.  Really take your time
and check your work closely.  No wires are crossing the PCB right?

Save your hair  - we'll figure it out!
-Don

Hey there, thanks for the reply.. No i havent got the 4:1 and 8:1 ratio sorted.. Im kinda stuck on it pulling my hair out to be honest!! :-( No the noise isnt a hum, its a noise when i move the output pot. its not the pot thats causing it tho as original i had mixed up the output and release pots and was getting this noise on the output pot, however when i switched the pots round i was still getting it on the output pot which was my original release pot. here is a recording of the noise

https://www.dropbox.com/s/eco3q5gwthrzumx/1176%20noise.mp3

any help would be greatly appreciated..

Hi all thanks for the help so far.. So i switched the output and release pots and that seems to have worked with my release time issue. However im still getting no compression on ratios 4 and 8.. It seems to be compressing perfect on 12 and 20.. Also i thought i had an issue with a noisy pot on my original output pot (which ended up should have been the release pot). However when i switched them round im still getting a noise when i turn the output pot and not the release pot. This would lead me to believe its not the pots and a separate issue on the output as iv been getting this noise on the output with the 2 different pots.. Any help or ideas would be greatly appreciated..

Thanks a million

I post 4194, you said 4:1 and 8:1 were intermittent? Are they still? Perhaps a bad batch of switches got out...

I'm guess the noise is the hum you mentioned on the previous page? Is it typical 50Hz  hum? I think this will likely be unrelated to the 4:1/8:1 problem, but I should ask, have you tied PCB ground to chassis? What I mean is did you run a wire from the negative side of one of the PSU filter caps out to your star ground or anywhere?

 

[Govinda Doyle]

hey there!
just wondering if anyone has the pdf skyler made and hosted on equinox systems site for the 1176 wiring guide?
Unfortunately their site if down at the moment or maybe permanently?
G

 

[avieira]

I just ordered a partial kit from Hairball and went to order the BOM from Mouser only to find out some of the parts are backordered.  I found suitable substitutes for the backordered parts and thought I'd share the BOM. 

http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=5d51ff9ac1

 

[mnats]

hey there!
just wondering if anyone has the pdf skyler made and hosted on equinox systems site for the 1176 wiring guide?
Unfortunately their site if down at the moment or maybe permanently?
G

As mentioned several times there are errors on that drawing and it doesn't apply to the currently supplied boards.

But I'm sure lots of people have it as this thread proves (burnt R32 anyone?)

The wiring guide that Hairball hosts is probably better than mine but as also mentioned before the schematic is the definitive guide to wiring your limiter.

 

[Govinda Doyle]

Thanks Mnats!
Legend!
G

 

[rosestudios]

Judging from your readings, it appears that your unit is over compressing.

• Have you done a complete voltage comparison as per the "schematic with voltages"  guide?
• Tripple check that you have all the transistors in the correct positions and seated correctly.
• Input transformer is seated correctly.
• output pot and release pot are not swapped (rels should be 5M)

Here are my findings regarding the DC voltage readings of each of these transistors.  Started to see some major discrepancies in the GR Meter Driver and then the GR Control Amp Section.  Any more assistance regarding these values would be great.  I will also post mnat's 1176 Rev. D Schematic with DC Reference Voltages. 

Some of these values are within 10% but I posted any differences I thought might be significant.

Q2: Good
Q3: 11.45V @ Collector, all else good
Q14: 10.86V @ Emitter, all else good
Q4: 4.79V @ Collector, all else good
Q5: 25V @ Collector, all else good
Q6: 26.6V @ Collector, all else good
Q11: 14.2V @ Drain, all else good
Q12: 14.2V @ Collector, Emitter at -1V, Base good
Q13: -0.3V @ Base, 13.5V @ Collector, -1V @ Emitter
Q7: 14.6V @ Collector, 3.7V @ Emitter, Base good
Q8: 14.6V @ Base, 13.9V @ Emitter, Collector good
Q9: 16.4V @ Collector, 2.6V @ Emitter, Base good
Q10: 15.8V @ Emitter, all else good

Appreciate the assistance.

 

[dbonin]

jusy fyi - the schematic with voltages is from mnats - not me.

 

[mnats]

I will also post mnat's 1176 Rev. D Schematic with DC Reference Voltages...Any more assistance regarding these values would be great.

By posting this I think it only serves to separate this document from the pages it is linked from.

If you looked at the FAQ that all the revision's voltage charts are linked from you would have many avenues to pursue without having to ask where you should look next. So could we please reference the troubleshooting FAQ linked from the first line of the first post of this thread instead?

 

[rosestudios]

I'm following up to the personal assistance I've been receiving from dbonin.  To be honest, even though the GR Control Amp is a little low it's still within 10%, and the Meter section is obviously off because I had calibration issues but it's still not clear how to resolve these, although the meter is less important than my diagnosed over compression. 

Seeing that, my values are fine and yet I'm still having over compression, my input transformer is seated correctly and my attack and release pots are not reversed.  I am wondering however why the voltage at Q7's collector is the same as Q8's emitter, while the schematic implies that at Q8 is the referenced lower.  It seems like this problem doesn't have an easily referenced answer?

The FAQ only asks to test components around the trouble areas but the only possible trouble area I find is between two connected transistors, Q7 and Q8, which don't have components surrounding them that would yield an answer as to why there's no voltage difference.

 

[mnats]

I am wondering however why the voltage at Q7's collector is the same as Q8's emitter, while the schematic implies that at Q8 is the referenced lower.  It seems like this problem doesn't have an easily referenced answer?

The FAQ only asks to test components around the trouble areas but the only possible trouble area I find is between two connected transistors, Q7 and Q8, which don't have components surrounding them that would yield an answer as to why there's no voltage difference.

There should be a Vbe drop on Q8.

What I read (from my own FAQ) is:

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. It may be a problem with the transistor itself or some other component, solder bridge, poor joint or mis-wiring as stated above. Test each component surrounding and including the transistor that gives the wrong voltage(s). Please note that I am not suggesting that you measure voltages and post them to the forum! If the voltages are wrong, you either have a faulty or incorrect component(s), component(s) inserted the wrong way, solder bridge or poor joint, mis-wiring, or you are simply measuring incorrectly.

 

[the groke]

Following up on my earlier posts (please see page 211 of this thread), what one should expect for voltages in the meter section prior to calibration? I'm having a hard time figuring out where to even look for the problem that is causing my Q biasing issue, since I cannot even get past the first step in calibrating the unit.

My voltages do seem on target in the other sections, and I can even make them close to the calibrated measurements in the meter section if I change the front panel 0 set, but I'm guessing I shouldn't be doing this. And it still does not even solve my Q-bias issue anyway.

I hope someone can help… 

Thanks D

 

[the groke]

Hi - Maybe some more info will help someone to help me find my Q bias problem (see page 211):

I can measure AC at pin 2/3 of output, but it is very low. Right now, the highest I can get is  ~.440V when the output is at 0. Again, this is nowhere near the 2.44VAC stated in the manual.

I have signal throughout the entire preamp and line amp sections, right up to the output (using a signal tracer to test).

Connections to the meter board seem fine.

I double checked all my resistors in both amp sections.

The uncalibrated voltages seem close to what they should be.

One exception that I did not notice earlier is at Q6. I measures 27.32V and 2.2V, instead of 28.93V/2.2V as specified on the voltages version of the schematic. Is this a critical difference? If the resistors in that region measure OK, where should I look for what is pulling it down?

Thanks D

 

[Echo North]

Hi - Maybe some more info will help someone to help me find my Q bias problem (see page 211):

I can measure AC at pin 2/3 of output, but it is very low. Right now, the highest I can get is  ~.440V when the output is at 0. Again, this is nowhere near the 2.44VAC stated in the manual.

I have signal throughout the entire preamp and line amp sections, right up to the output (using a signal tracer to test).

Connections to the meter board seem fine.

I double checked all my resistors in both amp sections.

The uncalibrated voltages seem close to what they should be.

One exception that I did not notice earlier is at Q6. I measures 27.32V and 2.2V, instead of 28.93V/2.2V as specified on the voltages version of the schematic. Is this a critical difference? If the resistors in that region measure OK, where should I look for what is pulling it down?

Thanks D

That seems within 10% which should be fine.  Are you doing these tests with GR off?  Are you sure your GR off switch is wired correctly?

 

[the groke]

Hi. Thanks very much for your reply. I checked over everything many times… which is why I now feel like a complete idiot for discovering that I had switched the orange and red wires on my output transformer. Thanks for the hairball dope slap to make me check the output wiring yet again. At least I mixed up two similar looking colors…

So, I have now gotten through the first two calibration steps just fine, but I'm having issues with the third step. When I move my shorting pin back to "normal", my VU meter drops as expected. The problem is that I don't have enough turns left on R71 to bring it back to zero. I searched on the forum, but can't find any real solutions for this… any thoughts?

Thanks D

 

[the groke]

Re my Gain Reduction Meter Tracking Adjustment question. I thought about it a bit more and realized that I can probably just adjust R44 to bring the meter back up to zero for the first set-up step. It was probably not centered when I started my calibration. Will try this later today…

EDIT:

This approach is not working. I can set the Meter Tracking via the front Input/Output procedure (I can get .775 and 2.44V), but my attempts to manipulate both R44 and R71 are failing. The basic problem is that when I switch the compression on, my VU drops all the way leftward, and I cannot get enough turns to bring it up to -10. In fact, under most conditions, I cannot get it to move rightward at all.

However,  I noticed that if I adjust R71 to its furthest rightward position (with the VU still reading 0 when attack is set to off), that I can use R44 to move the needle slightly to the right (when compressio is switched back on), but only to about -18 on the VU. After that, R44 stops being effective.

Should I switch in a 5k trimpot for R44, or does this signal some other issue/s?

I've tried going through all the various iterations of this procedure that exist online. Some do not even mention R44 - others refer to components from different builds, and my attempts to extrapolate what to do are failing.

EDIT 2:

I tried the dbonin approach on YouTube. Still not working (very clear explanation in the video though). All fails when it comes time to adjust R44 to bring up the meter to -10.

Please help… I'm so close….

Thanks D

 

[muffy1975]

team,


sorry to change the subject but should there be an equal audio output on pin 3 of the output xlr as there is on PIN 2 but just reverse phase?

I can only measure my input sine wave on  PIN 2 of the output XLR . PIN 3 seems to carry very little audio. What am i missing here? Pin 1 is earth.

regards


Michael

 

[Harpo]

I can only measure my input sine wave on  PIN 2 of the output XLR . PIN 3 seems to carry very little audio. What am i missing here? Pin 1 is earth.

Transformer output is floating balanced. Your output is between XLR-pin 2 and pin3 (not between pin2 and 0V or between pin3 and 0V). XLR-pin1 is connected to chassis/shield in the shortest possible way and is not involved in your measurement.

 

[muffy1975]

Thankyou Sir,

of course

Cheers

Michael

 

[treyd]

Issues with : Gain Reduction Meter Tracking Adjustment / Attack pot adjustment doing anything/ Ratio selection doing anything

I just finished my build.  Powers up, passes sound, input and output seem to work, and all calibrations seemed to go ok until I got to : Gain Reduction Meter Tracking Adjustment.  I still hadn't listened to the unit, but this wasn't working right.... after several unsuccessful tries at calibrating this step, I decided to give 'er a listen, and what I found was while it would pass sound beautifully and the input and output knobs worked (in addition to the appreciated lack of smoking, poping, etc.) I could not get any noticeable effect from the Attack knob (from Off to full on) nor from the Ratio buttons EXCEPT that selecting '8' would cause the unit to get much louder then fade back to the original volume in a few seconds.  Also, pressing in
'GR' does nothing but always stay at '0' whether audio is passing through or not.  I'm likely hearing no compression as well.

I've checked my wiring and resistor values.  Everything looks ok, but I should mention one thing:  during the build phase, the green wire that goes from the attack pot to the ratio pcb had to be rerouted as I damaged the contact around the hole on the back of the pcb.  I examined the pcb and found that the route in the pcb lead directly below to where the '20' buttons top middle lead came through the pcb and the original hole didn't seem to lead to any other point on the pcb.  This was the only point of weakness I can find with my build, but surely I must be missing something and surely someone has had this problem before. 

Suggestions?  Thank you!  I'm at a loss.....

 

[tzujan]

Hello, I have been lurking for a long while, and now that I have the MNATS/Hairball Kit I have my first question.  I am showing a greater that 1 ohm reading on my DMM, for one side 15-45 ohms.  Everything else checks out - the other side and the back panel all under 1 ohm, at .2.  In the Hairball manual it states "clear some additional powder." I assume this would be in reference to the hole that is already cleared - directly next to the IEC inlet.  For good measure I cleared more, same readings.  Shall I clear off addition powder coat from where the "bad" side meets the rear and bottom panel? Or is there something else I should check / do?

Thanks!
Brian