[BUILD] 1176 Rev A - Back to the beginning...

[dmp]

Can you zero the meter in GR mode?

 

[mikerl]

So i have built the 1176.. it LOOKS great.  there are a few issues.. one is that if i crank the input, output and a preamp in front of it, i get signal, however, its very small and metalic sounding.  The other is that when i switch my meter from +4 to GR, the meter needle does not move from the left (down) to the 0db range.

i assume the second issue will be easier to resolve than the first.

The power supply voltages are in good order. 

EDIT>>>>> 


SO the compressor and the meter are working.  I went throughout the calibration process.. and the only issue i have is that i cannot get the null adjust to read 0.00 vdc.  the range of the pot gets me from about 0.43 vdc to 0.75 vdc.  Not sure why i cant get my measurement correct here. 

Mike

 

[mikerl]

Any thoughts on my inquiry above?  i didn't get any feedback, im assuming because I edited my post 4 times as i worked out issues, so i figure i'll put my current debacle here.

"SO the compressor and the meter are working.  I went throughout the calibration process.. and the only issue i have is that i cannot get the null adjust to read 0.00 vdc.  the range of the pot gets me from about 0.43 vdc to 0.75 vdc.  Not sure why i cant get my measurement correct here"


Thanks!

 

[olebrom]

Hi

Just finished building the rev a 1,25 version and it sounds great Everything is working except I get this weird oscillation when i turn the output pot up. Its working fine from minus infinite to around -12  (3 o clock). At - 12 there  is a loud "thumb" and the music distorts really badly. If i turn of the music i can still hear the "thump" around -12 and past -12 up to 0 there is "weak high frequency radio sounds" that goes down in volume as i approach 0 db (full volume). (Oscillation?)  I have checked that all my ground is connected. C25 goes to the "chassi" of the output transformer and I have measured that the ground is getting to all the parts (as described in mnats wiring guide)

Would appreciate if  someone more "technical minded" than me could help me with this issue

Thanks

 

[mac]

Any thoughts on my inquiry above?  i didn't get any feedback, im assuming because I edited my post 4 times as i worked out issues, so i figure i'll put my current debacle here.

"SO the compressor and the meter are working.  I went throughout the calibration process.. and the only issue i have is that i cannot get the null adjust to read 0.00 vdc.  the range of the pot gets me from about 0.43 vdc to 0.75 vdc.  Not sure why i cant get my measurement correct here"


Thanks!

Hey Mikerl,
Mako's video for null adjust is done on a Rev D board. For the blue rev A we need to put in pins at the TEst Points TP10and TP11. Then try the procedure again. You should find it works!!

Mac

 

[mac]

oh ....and once you get to the meter tracking adjustment, double check your value of R44. I only just got back to finish a Rev A that has been sitting on the bench, and was wondering why I hadnt put a 5k trimmer in R44, (I was working off an old BOM).

Mako has made updates to the latest bom and board silk for 5K in this spot.

Take your time with the calibration and remember:
- let the unit warm up for half an hour first;
-make sure you get the Q bias adjustment right (even if you go through the process a few times),
- make small changes to the controls ( 0 and -10 are often closer than it seems, and sometimes the direction of adjustment is a bit counterintuitive too  ;D);
- don't be afraid to walk away....come back and start again.....

Every time I put one of mine on the bench for calibration, it's like I re-learn the process every time.

Mac...

 

[Ilya]

Just finished building the rev a 1,25 version and it sounds great Everything is working except I get this weird oscillation when i turn the output pot up. Its working fine from minus infinite to around -12  (3 o clock). At - 12 there  is a loud "thumb" and the music distorts really badly. If i turn of the music i can still hear the "thump" around -12 and past -12 up to 0 there is "weak high frequency radio sounds" that goes down in volume as i approach 0 db (full volume). (Oscillation?)  I have checked that all my ground is connected. C25 goes to the "chassi" of the output transformer and I have measured that the ground is getting to all the parts (as described in mnats wiring guide)

This is exactly my problem as well. From what I can tell, this is definitely ultrasonic oscillation. It's possible to shift the oscillation point further by moving the wiring around (for example, moving wires from the output XLR to meter board further from input circuit). However I couldn't get rid of it completely.

What layout are you using? I've made a layout myself. Are you using mnats boards or have you made your own? I believe it's mostly a layout issue, but I haven't got enough responses from the builders to confirm this.

You can also check the flux residue. It may cause enough leakage to disrupt high impedance circuits.

Regarding where oscillation starts, I suspect 2 points. Either the input circuit that gets the output signal fed back somehow (through capacitance coupling probably, or some sort of leakage). Or sidechain. I suspect sidechain because when I touch some sidechain components the oscillation disappears, but comes back quickly as soon as I remove a hand.

 

[mikerl]

[/quote]

Hey Mikerl,
Mako's video for null adjust is done on a Rev D board. For the blue rev A we need to put in pins at the TEst Points TP10and TP11. Then try the procedure again. You should find it works!!

Mac
[/quote]

Thanks MAC!!!! a rather simple thing for me to overlook!  I'll get on this as soon as i get home!

 

[evilcat]

I'll have to use an external power supply for my next rev A : a JLM power station, 2 rails for the 1176, and 2 rails+48V for a VP25 preamp.

On the 1176 PCB, PSU section, what parts should I remove ?
What parts should I leave ?
Where should I connect my +30V and -10V ?

Thanks,

Ben

bump anyone ?

 

[Ilya]

I'll have to use an external power supply for my next rev A : a JLM power station, 2 rails for the 1176, and 2 rails+48V for a VP25 preamp.

On the 1176 PCB, PSU section, what parts should I remove ?
What parts should I leave ?
Where should I connect my +30V and -10V ?

This depends on the revision of your board. It's easier to look at schematic and remove all the PSU section components. After that trace +30V and -10V lines and connect to them in any convenient point. If I recall correctly, V2 board has pads for external PSU connection.

I've attached the drawing for your convenience.

Why on earth do you need 2 lines of phantom voltage? 1 will be plenty enough for many channels.

 

[evilcat]

That's what I thought, thanks Ilya, I wanted to be sure.
No I don't need 2 lines of phantom power !!! I'll have 2 rails for the preamp (+/-16V) and 1 for the phantom power. Just a typing error

thanks again.

ben

 

[buildafriend]

Hey guys, I was wondering if I could ask you a question that many of you might find to be kind of obvious.

In the MNATS 1176 Revision A Version 1,2,5 PCB  (dated 05,12,2010):

http://mnats.net/files/1176REVA_125_VOLTAGES.pdf

What is C16 doing?

What is C6 Doing?

What would be the best kinds of capacitors to throw in for these? I was thinking ceramic disc caps but since I don't see any other ceramic disc caps in the circuit it made me think twice. Maybe mica would be best for the application?

I am finishing this build for a friend, C6 and C16 were missing. Along with Q13 (2n3707), R50, and R9.

Thanks regardless.

 

[websoul]

Hey all, first post!  I've been reading this for a long while and now got my own kit set up.  Just have a quick question about the input transformer (altran 3837).  I've soldered to the board and when doing a continuity test, it bleeps when you test the + - points on both the input and output of the Hairball xformer board (it's not wired into the case yet).  Is this ok or is the transformer no good?  Just wanted to check before I start.

BTW, this forum is fantastic, I've answered all my other questions by searching this thread, I just couldn't see anything specific regarding this.

Thanks in advance!

 

[Echo North]

Hey all, first post!  I've been reading this for a long while and now got my own kit set up.  Just have a quick question about the input transformer (altran 3837).  I've soldered to the board and when doing a continuity test, it bleeps when you test the + - points on both the input and output of the Hairball xformer board (it's not wired into the case yet).  Is this ok or is the transformer no good?  Just wanted to check before I start.

BTW, this forum is fantastic, I've answered all my other questions by searching this thread, I just couldn't see anything specific regarding this.

Thanks in advance!

That's fine.  The windings are that, just one long piece of wire wrapped around a core.  The + being one and and the - being the other.  The DC resistance is based on the length of that wire.  For many transformers that may only be a few ohms so it'll beep.  For other it may get up to 100 or 200 ohms.

I believe those 3837's have a very low DC R.

Having no continuity or very high DC R is a problem (broken wire).

Mike

 

[websoul]

Hey all, first post!  I've been reading this for a long while and now got my own kit set up.  Just have a quick question about the input transformer (altran 3837).  I've soldered to the board and when doing a continuity test, it bleeps when you test the + - points on both the input and output of the Hairball xformer board (it's not wired into the case yet).  Is this ok or is the transformer no good?  Just wanted to check before I start.

BTW, this forum is fantastic, I've answered all my other questions by searching this thread, I just couldn't see anything specific regarding this.

Thanks in advance!

That's fine.  The windings are that, just one long piece of wire wrapped around a core.  The + being one and and the - being the other.  The DC resistance is based on the length of that wire.  For many transformers that may only be a few ohms so it'll beep.  For other it may get up to 100 or 200 ohms.

I believe those 3837's have a very low DC R.

Having no continuity or very high DC R is a problem (broken wire).

Mike

Brilliant, thanks Mike 

 

[outoftune]

I'm still looking for info on adding the threshold sensitivity trim. I can see the spot on the PCB, but I haven't been able to find info on the value of the trim pot and the setup procedure. Is anyone able to help out? My 1176A is already working fine, just with a sensitive threshold.

 

[ethervalve]

I'm still looking for info on adding the threshold sensitivity trim. I can see the spot on the PCB, but I haven't been able to find info on the value of the trim pot and the setup procedure. Is anyone able to help out? My 1176A is already working fine, just with a sensitive threshold.

Hey T, Mako talked about this in the revD thread:
http://www.groupdiy.com/index.php?topic=20058.msg258435#msg258435
Did you try the later serial # mods that were discussed in this this thread? I did and they seemed to make my Rev A less grabby.
Edit: There was a separate thread that talked about this: http://www.groupdiy.com/index.php?topic=34502.0
Good luck!

 

[remsouille]

Hey there folks!
First of all, thank's a lot for all the great information here on this forum.
I just finished my first 1176 A build, and there's a problem with the gr part. My input and output work fine, the +4 and +8 on the VU as well. But: no compression, and VU doesn't work on GR mode (needle stays down). With pad 7 connected, there is a huge drop in output volume, and when out, I get the volume it seems I should get. I checked all the voltages against the mnats schematic, everything is fine EXCEPT in the GR meter driver section.
On Q11 I read about 2/3 volts on every pin, and then positive voltage on Q12 where It should be negative.... There is negative voltage coming all the way to r66 though, but out of R66 it's positive...
So I thought Q11 was fried, then replaced it, but nothing change. I don't actually think that the problem comes from the Gr meter section itself, cause if it did, it wouldn' affect the output volume the way it does, would it?
I think the problem occurs between Q10 and dot 7, but I checked continuity and wiring, and everything SEEMS fine.... Any measurements in this area from a working unit would be much much appreciated!

 

[websoul]

Just wanted to post that my Rev A is up and running.  Loads of great info and people here.  The Hairball kit is easy to put together and the Mnats board is very straightforward.  Thanks everyone.

I'm just going through the calibration at the moment.  Q Bias and Null adjust went through just fine, but step three, the meter adjust isn't quite working.  When turning the gain reduction off in +4 mode, the VU meter doesn't move.  I don't think I'm passing enough signal through?  I've played some sounds through and it sounds real great when gain reduction is bypassed, but sounds a dodgy when gain reduction is turned on.  I'm thinking it's a dry joint somewhere or maybe a short somewhere?  I can hear the compression working (even though the final calibration isn't complete), but just sounds very dirty, so hoping I'll nail that pretty soon.

Looks like I'll have to get another one ordered in now though  :

 

[remsouille]

Hey, any help on my inquiry above? One funny thing I noticed is that when dialing the attack, release and ratio controls, I can see slight gain reduction changes in +4 and +8 modes... Any ideas??