[BUILD] 1176LN Rev D DIY

[dalmaproductions]

Thanks mnats! But in this case the drifting does not settle with time. It actually gets a bit worse, and keeps drifting up and down indefinitely.

Any ideas on what I can measure?

I'm considering changing out all the FETs?

 

[mnats]

Thanks mnats! But in this case the drifting does not settle with time. It actually gets a bit worse, and keeps drifting up and down indefinitely.

If you are suggesting that I misunderstood your issue, I did not. Please read the FAQ carefully.

 

[tondon]

Is it ok to use a 2k trimmer for r44, same as the others, or does it have to be a 1K? The silkscreen labels it as 2k but it's 1K on the parts list.

 

[mhuss]

Is it ok to use a 2k trimmer for r44, same as the others, or does it have to be a 1K? The silkscreen labels it as 2k but it's 1K on the parts list.

I used a 2k, it works well.

 

[mhuss]

I have a pair of mnats rev D boards and the Hairball red link boards.  The individual channels work well, but the link only works on one channel. I'm having a devil of a time trouble shooting this because...

Has anyone gotten around to creating an 1176D  schematic (or marking up an existing one) that shows all the mnats board connections? I'm having a heck of a time trying to match up the rotary ratio and meter board connections to the stock UA 1176 schematic.  It would also be incredibly handy to have the mnats board connection #s marked on the schematic. Anyone?

 

[junkface]

http://groupdiy.com/index.php?topic=44882.60

 

[mhuss]

Thank for this, I already have mrerdat's excellent layout image (which I used during my build). I have double- and triple-checked that the wires are connected the same way on both channels.

I was wondering if anyone had annotated a /schematic/ with the board connection numbers that I could use for troubleshooting.

 

[trashcanman]

This is more of a general question I guess but I'm building a rotary switch version of the 1176 and was wondering if other people who have also were able to use collet knobs on the switches. I bought 10 collet knobs and trying to use them on the switches I had for ratio and meter display was impossible as the switches were so stiff, the knobs couldn't grab hold of the shaft, so to speak. These switches were ancient russian things I got off ebay so that might be why. I'm thinking of doing stepped attenuators for the input and output and I'd like to use these knobs, would new switches be easier to turn?

 

[mask]

Hey,

I finished my build of the V2.2 25.02.13 1176LN REV D mnats version, but I still have some unresolved issues and wondered if one of you might be able to help me.

My main issue is the following:
SETUP:
- GR-Mode (with and without gain-reduction circuit in action)
- Ratio: arbitrary
- Attack: arbitrary
- In/Output: arbitrary
- warm-up time >30mins
ISSUE:
- NO input signal: when I turn the release knob from all the way CW to CCW the meter changes from 0dB to about -10dB
-  With input signal: the compression seems to work fine when all the way CW. When turning CCW the meter moves to the left, the movement of the meter-needle gets smaller.  When Release is turned all the way CCW, it pretty much stops moving at all and the needle is at about the same spot where it was without any input signal.

Additional issues:
ISSUE&ACTIONS:
The unit has a very long warm-up time. In GR mode the unit drifted about 5dB during the first 30-50 minutes (what is a normal warm-up time?). I followed the hint by hairball (http://www.hairballaudio.com/blog/resources/build-guides/populating-the-pcb-) to switch out the 2N3707 with 2N30708. I matched a pair with very high hFE values (449 and 450) and made sure that the temperature drift of the two was very similar. Additionally, I followed the FAQ by mnats and cleaned of flux and foreign substances of the board. I made sure that the external temperature did not change during the new tests. I calibrated the unit after a warm-up time of over 50 minutes. I calibrated both with mnats technique, which I personally like better since I better understand what’s going on and also with the hairball calibration guide. The calibration settings were as expected very similar.
RESULTS:
The warm-up time remains very long. During the first 30-50 minutes the unit still drifts about +4dB.

More information:
I double-checked all connections and the wiring in general. I am fairly confident that I did not mess up there. I also checked the voltages and compared to the standard voltages suggested in the FAQ (http://mnats.net/files/1176REVD_VOLTS.pdf). When the release knob is turned all the way CW the voltages seem fine. I attached a picture of my voltages (black: suggested, pencil: my valuse). Does someone know how much variation from the suggested values is normal/OK? When I turn the release pot CCW, the voltages at Q11 change which kind of makes sense to me when looking at the routing (highlighted path). The values after release is all the way CCW for Q11 are behind the little arrows. But if I just think about it without looking at the circuit, with or without an input, the GR meter should not be affected by the release that much. Right? 

If you have any suggestions for what I could try, I’d be very happy.

Thanks!

 

[BaZZZZZ]

- NO input signal: when I turn the release knob from all the way CW to CCW the meter changes from 0dB to about -10dB
-  With input signal: the compression seems to work fine when all the way CW. When turning CCW the meter moves to the left, the movement of the meter-needle gets smaller.  When Release is turned all the way CCW, it pretty much stops moving at all and the needle is at about the same spot where it was without any input signal.

Hello! I have similiar problem) And now can't solve it too)

 

[Echo North]

I've seen this before but unfortunately can't remember the cause.

Make sure you don't have your output and release pots mixed up. 

Other than that I would suspect wiring. DO a lot of continuity testing...make sure terminals have continuity.

Mike

 

[mask]

Hello,

thank you for your answer.

I am certain, that the pots are not mixed up. I checked all of them multiple times. I even desoldered them, and measured them without anything attached to make sure they were working properly.

The wiring should be fine too. I first build the rotary version and had the described problem. Because of that I switched to the push button version, hoping it would resolve my issues. Doing that I switched out all the wiring. But the problem did not disappear. Therefore, I think the wiring is not the problem.

I was suspecting a continuity issue too. Because of that I measured from component to component for every wire (component the terminal is connecting to on main pcb to component on the other end of the wire). I did not find any issues there either.

I am wondering if it might me a dead capacitor or fet generating a ground loop or something. I am measuring the darn thing for days now. I am starting to go crazy :/

Is there any schematic with resistance values after everything is soldered to the board?
Is there a schematic with more voltages?
Can anybody tell me how the voltage for the three Q11 terminals and/or on the pot side of R65 (pin 7 on main pcb) changes with turning the release in a working unit (all relative to ground)?

Thanks for your help!

 

[ncoak]

hey guys, I built a rotary rev. D a while back...love it and use it constantly, but lately it has been giving me some problems. upon first turning it on, everything works great, but after a while (20-30 mins?) the compression invariably ceases to kick in. this can sometimes be resolved by turning the unit off and on again (but it always comes back). i'm sort of dreading cracking this guy back open, anyone have any ideas about where i should start looking, or experienced any similar issues?

thanks!

edit: just saw the discussion a few pages back on the same issue, will do some poking around and check back!

 

[mnats]

- NO input signal: when I turn the release knob from all the way CW to CCW the meter changes from 0dB to about -10dB
-  With input signal: the compression seems to work fine when all the way CW. When turning CCW the meter moves to the left, the movement of the meter-needle gets smaller.  When Release is turned all the way CCW, it pretty much stops moving at all and the needle is at about the same spot where it was without any input signal.

In a correctly wired unit a CCW rotation will give the maximum release time. But your symptom suggests that the voltage at point 7 is getting shunted to some fixed level as it is rotated CCW - exactly the opposite of what you would expect.

With power off and the CW lug of R56 disconnected measure the resistance from the end lugs with the knob at each extreme. It should never measure less than 270k||5M. If OK, then check the wiring of the CCW lug very carefully. See if that lug is currently showing low resistance to ground.

 

[mask]

Hey,

I finally got it working!

ACTIONS:
I first did the measurements for the pot suggested by mnats. I had done similar measurements before, but I was hoping that I might find something interesting while doing it. They turned out to be all perfectly fine.

As mnats wrote in his answer and I suggested before too, the symptoms suggested that the voltage at point 7 was getting shunted. For that reason I again followed the yellow path on the diagram I posted. I checked all parts and connections on the bottom of the PCB. Since I had used flux cleaner before to clean of the board most of it looked fine. But of all parts, Q11 had some flux residue left. I cleaned that and realized that there might also be flux and residues on the top side. I checked and found a huge blob of flux stuck underneath Q11. I removed that and also carefully cleaned the whole top with flux remover and a little brush. Especially the whole path connected to 7.

Sure enough after I fired up the unit again it worked. So I guess the post in the FAQ was all the answer I needed after all.
I am a little embarrassed that I did not think about the flux residues on the top side of the board before.

RESULTS:
The warm-up time is reduced to about 5-10 minutes and the needle only moves about +1dB within this time (what is an average warm-up time?).
The release is now doing what it is supposed to do and all other functions of the unit are as expected.

Thank you all for helping me out with this issue!
__________________________________________

On an unrelated note:
While I was searching the internet for similar problems (instead of properly cleaning my board ), I found a bunch of suggestions to swap out some of the adjust-pots for larger values. e.g. R59, Q-Bias ADJ for a 5k or R71, Zero-Set for a 5k. Furthermore, I found a post which suggested that you could swap out R55, Attack for a larger value 50k-250k to be able to get longer release times. I am not really interested in doing any of these mods anymore. The only interesting thing might be to do the attack time mod under the condition that it does not change the original behavior of the unit.
Now, if these parts would just be rheostats (only two terminals A and W), I would agree with the swaps. But since they are pots, they have three terminals (A W B or 1 2 3) with the resistance between A and B always being the maximum value.

So lets say we switch out Q-Bias with a 5k pot. Since R59(A-B) is parallel with R60 and R35 is in series with them the resistance would change from (2k||3.9k)+10k to (5k||3.9k)+10k. Right?
Also and more interesting the attack-pot-mod. The resistance between point 19 and 7 is R55(A-B)||(R54+R55(A-W)). Therefore, when I swap out R55 from 25k to 50k, R55(A-B) would change and with it the total resistance.

Long story short: Which of the adjust pots and control pots can be switched out for larger values and why does or does it not affect the unit.

What I've read so far:
- ATTACK (R55): switch out attack for larger value to be able to have a longer attack time, (without affecting???) original characteristics (https://www.gearslutz.com/board/11855403-post12.html) - I would expect a change in characteristics
- Q-BIAS ADJ (R59): switched for 5k to solve adjustment issues (sorry, can't find the link right now) - I would expect a rather negligible change in characteristics
- TRACKING (R44): switch out for larger value, when running out of range while doing the Gain Reduction Meter Tracking Adjustment (http://groupdiy.com/index.php?topic=20058.msg461269#msg461269) - it makes sense why this mod works and does not change any characteristics (works like rheostat)
- DISTORTION (R85): seen people switch it to smaller value for more precision - personally I don't see the advantage, but I don't see a problem with changing it either to a smaller or larger value (works like rheostat)
- NULL-ADJ: switch for 5k (I think it was because the person did not have 2k pots)
- 0-Set: larger value for larger range - I think it influence the characteristics

If anyone has more information, please let me know.

 

[denov]

hey all!

my first post, first 1176 build. 

i think there's something not right.  when i have it set for step one for of calibration and see 0.775 on the in xlr i'm seeing 8.4v on the out and i can hear the tone, the meter pegs, i have to turn down the out to 8 o'clock to get the 2.75v and the q-bais trimmer doesn't do anything. 

i check values against this http://mnats.net/files/1176REVD_VOLTS.pdf  most things where right on, some within ~5%.  i have the right values for power.  i re-flowed all the joints.

where do i look next?

thanks

 

[Echo North]

hey all!

my first post, first 1176 build. 

i think there's something not right.  when i have it set for step one for of calibration and see 0.775 on the in xlr i'm seeing 8.4v on the out and i can hear the tone, the meter pegs, i have to turn down the out to 8 o'clock to get the 2.75v and the q-bais trimmer doesn't do anything. 

i check values against this http://mnats.net/files/1176REVD_VOLTS.pdf  most things where right on, some within ~5%.  i have the right values for power.  i re-flowed all the joints.

where do i look next?

thanks

Your output is super high and if it's high you'll here the tone in the output that's normal.

On your new FET/RACK V1.11 PCB there is test pads.  What is the DC (referencing ground/enclosure) at pad 18 AND pad 7 while rotating the qbias.  What is the DC at each test pad when rotating the qbias full CW and full CCW?

All four measurements.

Mike

 

[denov]

Your output is super high and if it's high you'll here the tone in the output that's normal.

On your new FET/RACK V1.11 PCB there is test pads.  What is the DC (referencing ground/enclosure) at pad 18 AND pad 7 while rotating the qbias.  What is the DC at each test pad when rotating the qbias full CW and full CCW?

All four measurements.

Mike

Q low (CCW)
  7  - 0
  18 - 0
 
Q high (CW)
  7  - -2.95
  18 - -3.0
 

i'm seeing different values on each side of R35 and R60.  from an earily post it looks it sounds like i should see the same value of each side.    what's the proper measurements and does it matter what side you test from?


is there a  list of mesaures for the other test points?

 

[denov]

where should the input be set to when getting the 0 dBu reference on the input to start the calibration?  should i you see a change in value on the xlr if you change the input?  just double checking it should be at 12 o'clock and that i'm not mis-reading the instructions.

 

[Echo North]

What happens to the DC at the gate of Q1 when you rotate the bias?