[BUILD] 1176LN Rev D DIY

[Echo North]

Hello folks!

I just got my 1176 D working and calibrated. It seems to be functioning right, but every time I power it up the meter needle is +/- 1db from zero. Is there something wrong?

Thank you!

Mikko

No it's the discrete meter circuit.  That's why they have the zero adjust on the front panel.

 

[sr1200]

Yeah let the unit warm up, the needle eventually makes its way to 0.... eventually lol.

 

[tronnyjenkins]

OK, so I guess I am being stupid, but I compared transistor voltages today to the actual MNATS ones. My Q11 aND Q12 are off and everything else is right within reason. Anyone have ideas of what might be amiss? I know Echo North won't be back until Monday... My "10.56V" is more like 17V, and the "9.26V" on Q12 is more like 16-17V as well...

Still not passing audio?  I'd put your unit in GR OFF mode and don't even worry about anything in the Meter or GR AMP section until you get audio passing.

Did you trace the signal through the unit?

Mike

Hey Mike, I'm very close. I had it passing audio this weekend (it just started working...) So I calibrated everything. However, I got it all racked up, etc, and go figure it doesn't pass audio. Weird. So I take it apart a bit ago and check through your list from the Rev A thread where I arrive at the input tranny. I couldn't measure anything on the secondary. I decided to unmount it from the case so I could be sure. Well then it works. I pass audio, try it out (still disassembled) on a vocal after passing the sine wave. So naturally I think cold solder joint. Well, I soldered all the points on the input tranny board, T pad, and PCB input, and now I'm not getting anything. How can I troubleshoot the input tranny?

 

[Echo North]

OK, so I guess I am being stupid, but I compared transistor voltages today to the actual MNATS ones. My Q11 aND Q12 are off and everything else is right within reason. Anyone have ideas of what might be amiss? I know Echo North won't be back until Monday... My "10.56V" is more like 17V, and the "9.26V" on Q12 is more like 16-17V as well...

Still not passing audio?  I'd put your unit in GR OFF mode and don't even worry about anything in the Meter or GR AMP section until you get audio passing.

Did you trace the signal through the unit?

Mike

Hey Mike, I'm very close. I had it passing audio this weekend (it just started working...) So I calibrated everything. However, I got it all racked up, etc, and go figure it doesn't pass audio. Weird. So I take it apart a bit ago and check through your list from the Rev A thread where I arrive at the input tranny. I couldn't measure anything on the secondary. I decided to unmount it from the case so I could be sure. Well then it works. I pass audio, try it out (still disassembled) on a vocal after passing the sine wave. So naturally I think cold solder joint. Well, I soldered all the points on the input tranny board, T pad, and PCB input, and now I'm not getting anything. How can I troubleshoot the input tranny?

Detach it from the main PCB and the Tpad but keep both of this wires attached to the transformer.

Measure the DC resistance between the two wires attached to the primary and then the two wires attached to the secondary.  I think they are roughly 40Ω and 13Ω.  Then check them to make sure you have infinite resistance between the windings and each winding and the shield.  Your shield may be intermittently touching a winding.

 

[lowend]

Hi !

I just finished a rev A and a rev D... Mike helped me to reduce the "hummmm" in revA and that's all right ! no "hummmm", no "bzzzz"

Today I calibrated the rev D.... Sounds good Compression OK, Voltage values OK....
BUT ! When I plug XLR output (1176 off without power) => I got a big "hummm"

When I plug IEC and turn ON the machine, the hummm disapear a little but still here....

Here is a little video you can see what happen exactly : http://youtu.be/3JkwkZgXauE

 

[lowend]

Hi !

I just finished a rev A and a rev D... Mike helped me to reduce the "hummmm" in revA and that's all right ! no "hummmm", no "bzzzz"

Today I calibrated the rev D.... Sounds good Compression OK, Voltage values OK....
BUT ! When I plug XLR output (1176 off without power) => I got a big "hummm"

When I plug IEC and turn ON the machine, the hummm disapear a little but still here....

Here is a little video you can see what happen exactly : http://youtu.be/3JkwkZgXauE

Someone has an idea ?  :'(

 

[jplebre]

what are you plugging it into? (bal, unbal?)
is your grounding correct (ie. ground hookup wire from supply caps present? shortest possible wire from IEC ground lug to chassis? IEC lead correctly wired? extension power plug ground ok? electrical installation?)

how's your O/p xlr grounded?

Cheers

 

[lowend]

what are you plugging it into? (bal, unbal?)
is your grounding correct (ie. ground hookup wire from supply caps present? shortest possible wire from IEC ground lug to chassis? IEC lead correctly wired? extension power plug ground ok? electrical installation?)

how's your O/p xlr grounded?

Cheers

I use balanced XLR...
The negative C25 is grounded... the case has a good electric continuity...
The hummmm is here when the mchine is off... not connected to electricity...

thanks for helping me did you see my video ?

 

[lowend]

Strange...
I unscrewed the output transformer... hummm still here... but when I move it, hummm's disappear...
Take a look : http://youtu.be/uBP0HKp4TMw

I dont know where from the problem .... Do you think bad output transformer ?

 

[jplebre]

Hey

Try and move the o/p wires to the meter. I had issues with some units placing wires for o/p close to i/p transformers.
doublecheck your ground connections (ie. close to 0ohm)

 

[lowend]

Hey

Try and move the o/p wires to the meter. I had issues with some units placing wires for o/p close to i/p transformers.
doublecheck your ground connections (ie. close to 0ohm)

nothing change...
looks like a magnetic field around the output transformer...
I double checked ground everywhere... I'm at 0,4 ohm maximum...

 

[lowend]

I just changed the output transformer.... that's the same...
Big "hummmm" when the machine is OFF and unplug...
Now the "hummmm" disapear when the machine is plug and ON (??!!)

EDIT :
Shame on me... I try to turn off my monitors amplifier and "hummmm" disappear !!! So I put the amplfier far away from the desk where compressors are....
My question is why the "hummmm" appear only with this compressor.... not with my Rev A....

 

[audiophreak]

Hello,
      sorry to jump right in  here ... I'm putting together a Dual Rev.D Rotary version and have noticed something when checking grounding. Still assembling but noticed that the Input  (-)  pad ( closest to the corner of the main PCB ) goes to earth Ground . Is this correct ?? or do I have a short somewhere.

also , I am using the old style ( multiple input trans input PCB ) do I still need to make that shield /ground connection under the Input trans PCB to carry shield to Input on Main PCB ??

  sorry if this has been covered , I have figured out alot just from looking at the schematic mnats provides at to the Rev.D and Rotary switches 

   

 

[jplebre]

I'm putting together a Dual Rev.D Rotary version and have noticed something when checking grounding. Still assembling but noticed that the Input  (-)  pad ( closest to the corner of the main PCB ) goes to earth Ground . Is this correct ??

Hello!
If you mean +- on the xlr = +- on the T-Pad = +- on the input trafo = + and earth on the pCB, that is correct)

( multiple input trans input PCB )

????????

 

[audiophreak]

If you mean +- on the xlr = +- on the T-Pad = +- on the input trafo = + and earth on the pCB, that is correct)

( multiple input trans input PCB )

????????

  Thanks jplebre  ;D    ... poor wording on my part ... multiple Input trans " foot prints "  = different  choices 

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

 

[mnats]

Still assembling but noticed that the Input  (-)  pad ( closest to the corner of the main PCB ) goes to earth Ground . Is this correct ?? or do I have a short somewhere.

Keep looking at the schematic 

also , I am using the old style ( multiple input trans input PCB ) do I still need to make that shield /ground connection under the Input trans PCB to carry shield to Input on Main PCB ??

Yes. You haven't specified which input transformer you're using but make sure that the can is tied to the chassis. This happens automatically with the Altran boards Hairball supplies but will need to be wired for the transformer board you're using.

 

[audiophreak]

Thanks mnats,
                          I'm using the LL1540  , do I still need to tie the shields together under the Trans PCB as the pics indicate for the hairball/Altran PCB , so that the input cable is shielded all the way to to the main PCB.

  I must say , your documentation on these projects is awesome !!  ... there's just a LOT of it  ;D

 

[tronnyjenkins]

OK, so I guess I am being stupid, but I compared transistor voltages today to the actual MNATS ones. My Q11 aND Q12 are off and everything else is right within reason. Anyone have ideas of what might be amiss? I know Echo North won't be back until Monday... My "10.56V" is more like 17V, and the "9.26V" on Q12 is more like 16-17V as well...

Still not passing audio?  I'd put your unit in GR OFF mode and don't even worry about anything in the Meter or GR AMP section until you get audio passing.

Did you trace the signal through the unit?

Mike

Hey Mike, I'm very close. I had it passing audio this weekend (it just started working...) So I calibrated everything. However, I got it all racked up, etc, and go figure it doesn't pass audio. Weird. So I take it apart a bit ago and check through your list from the Rev A thread where I arrive at the input tranny. I couldn't measure anything on the secondary. I decided to unmount it from the case so I could be sure. Well then it works. I pass audio, try it out (still disassembled) on a vocal after passing the sine wave. So naturally I think cold solder joint. Well, I soldered all the points on the input tranny board, T pad, and PCB input, and now I'm not getting anything. How can I troubleshoot the input tranny?

Detach it from the main PCB and the Tpad but keep both of this wires attached to the transformer.

Measure the DC resistance between the two wires attached to the primary and then the two wires attached to the secondary.  I think they are roughly 40Ω and 13Ω.  Then check them to make sure you have infinite resistance between the windings and each winding and the shield.  Your shield may be intermittently touching a winding.

It was a pad on the tranny board! As soon as I touched it to remove the wires it came off! Fixed and working 100% as far as I can tell.

Thanks Mike!

 

[audiophreak]

Hi mnats ,
                I flipped the switch for the first channel, all voltages from schematic checked and all ok, went through your awesome calibration video's and all went well until the Gain Reduction meter tracking ... I remember it took me awhile to get this right with the dual 1176 Rev.J's I did last year. 
     
    I just saw this post today and was wondering your thoughts on this, as in the last two posts of this thread are exactly what I'm getting ... Q Bias  and Discrete Meter circuit adjustments went fine, but when I get to the  Gain Reduction meter tracking , I can only seem to get a 6Db gain reduction no matter how I set input and output with 1k - 0Db at 20:1.
    I also thought maybe a problem with meter or ratio / meter board or possibly input trans.
  ... before I try this wanted to know your thoughts on this,
                                                                                                Thanks,
                                                                                                              Chip

http://www.groupdiy.com/index.php?topic=50547.new;topicseen#new

 

[audiophreak]

Just to clarify ,  with 1k@0db , input almost all the way up and output almost all the way down I get 4dbGR@20:1 , 5dbGR@12:1 , 6dbGR@8:1 , and 7dbGR@4:1    in VU mode shorting pad 22 to ground.

    Q Bias  and Discrete Meter circuit adjustments went fine and voltages from schematic are all good .... any Ideas ??  suggestions ??