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

[stitch-o]

Hello,
Finishing up a Rev A and ran into something:
1:20 button works but 1:12-4 buttons do no compression.
Everything else seems to be fine.

Any thoughts anyone?

Sounds like something is wrong with your offset switching. Check R63 on the ratio switch. Make sure it's 1.5K.  Check for continuity around it.  With ratio 4 selected, what is your DC at pad 21?

1.5k beeps out either side.
pad21 DC:
-2.3 @ 1:4
-3.1 @ 1:8
-3.8 @ 1:12
-6.3 @ 1:20

I went through and double checked all ratio
PCB values...Im bettin this is something stupid simple...

Thanks mang!

 

[Echo North]

Those look good.  What's your AC voltage at pad 22 going through the switches?


Check around R19 on the ratio.

 

[stitch-o]

Those look good.  What's your AC voltage at pad 22 going through the switches?


Check around R19 on the ratio.

AC @ pad22 is whatever input signal voltage is.
0 with no input signal.

R19 is the 130K? I replaced with a lower value, have triple checked
continuity...

maybe I wired the release/attack wrong? I'll look over that...

edit: when I jump any of the switches, I get compression action
along all 4 pushbuttons....of course its the 20:1.
Whats very odd too s that I went through and checked values
and continuity of all the resistors and switches and connections inbetween.
Except the 56K between the 4 and 8 switches....

 

[Echo North]

Hmmm pad 22 AC should be reducing in AC as you move from 20 -> 4.  The signal is taken from pad 15 (output pot) and fed through a voltage divider on the ratio switch.  If 20 is selected, it passes through R78 then to pad 22.  If 12 is selected it goes through R78 and R19 then to pad 22.  Look at the schematic and you'll see as you move down there is more R and the voltage is decreased.

Something is wrong in there.

 

[germoju]

Hi everybody

I just finish a Rev A and I begin the calibration. My problem is step 3 : I follow the instructions, but when I have to turn R44 (Trimmer 5K) to fix -10dB, nothing happen...
R44 doesn't work....
I check all but I dont see anything.... Step 1 and 2 are good....

I find something... I had a stereo link card on it... And at the step 3, when R44 doesn't work, I push the stereo switch, and now R44 is working BUT I cant see the -10 dB drop anymore, no more compression. To see the 10 dB drop, I have to push stereo switch again, compression is back BUT R44 doesn't work at thistime
I check + 10x everything but I can't find !

So I disconnect the stereo PCB. I plug the wire from the output pot to Ratio Bord pad 15 as a normal wiring, and calibration is OK ! R44 works perfecly but my 1176 has no stereo sidechain.
So the problem is from my Stereo link wiring ? stereo switch ? ... I cant see !!

Someone can help please ?

Here are some picture if you see something wrong, please tell me


_IGP5976 par volcanovap, sur Flickr


_IGP5977 par volcanovap, sur Flickr


_IGP5981 par volcanovap, sur Flickr


_IGP5978 par volcanovap, sur Flickr


_IGP5983 par volcanovap, sur Flickr


_IGP5982 par volcanovap, sur Flickr

 

[stitch-o]

Hmmm pad 22 AC should be reducing in AC as you move from 20 -> 4.  The signal is taken from pad 15 (output pot) and fed through a voltage divider on the ratio switch.  If 20 is selected, it passes through R78 then to pad 22.  If 12 is selected it goes through R78 and R19 then to pad 22.  Look at the schematic and you'll see as you move down there is more R and the voltage is decreased.

Something is wrong in there.

ooops, you are right, I had a drum loop unmuted with monitors down
: with sine wave
AC @ pad 22
20:1  1.17
12:1  .38
8:1    .22
4:1    .13

 

[Echo North]

Check your DC voltages of the 4 transistors in the GR amp.  The MNATS rev A page has the A schematic with DC voltages listed.

What is your DC V at the gate of Q1?

 

[stitch-o]

Check your DC voltages of the 4 transistors in the GR amp.  The MNATS rev A page has the A schematic with DC voltages listed.

What is your DC V at the gate of Q1?

Q10 is 7 - 30 - 7
Q9 is 4 - 7.5  - 4VDC
Q8 is 24 - 30 - 24
There is def something not right here.
Q1 is preamp no?

Getting 30.1 at the TP..

ok, Im look around at R47, R51

------
edit: R36, R38, R47, R51 all check out in tolerance.

 

[Echo North]

Q1 is the GR FET.  Just interested what your QBias is at.  It's the DC at the gate.

 

[stitch-o]

Q1 is the GR FET.  Just interested what your QBias is at.  It's the DC at the gate.

-1.8VDC

You are def on the right track with power issues in the GR section.
Maybe a bad transistor?
On a potential sidenote: I read a discussion somewhere on the value of the trimmers, should they be 2K?

 

[Echo North]

Your gate base voltages are too low.  If your rails are fine and the resistors are fine, you could try the transistors.  Start with the ones closest to pad 22.

Check ALL of the resistors in that section first.  R37?  Make sure that is a 470K and not 470R.

Mike

 

[stitch-o]

Your gate voltages are too low.  If your rails are fine and the resistors are fine, you could try the transistors.  Start with the ones closest to pad 22.

Check ALL of the resistors in that section first.  R37?  Make sure that is a 470K and not 470R.

Mike

Looks like R37 might be 47K...

 

[Echo North]

I would pull that and check that.  That would mess up your base voltage divider.

Sorry I keep saying "gate"...I work with FETs too much

 

[stitch-o]

I would pull that and check that.  That would mess up your base voltage divider.

Sorry I keep saying "gate"...I work with FETs too much

Freakin' BINGO!

Thanks Mike!!!!

 

[germoju]

Hi everybody

I just finish a Rev A and I begin the calibration. My problem is step 3 : I follow the instructions, but when I have to turn R44 (Trimmer 5K) to fix -10dB, nothing happen...
R44 doesn't work....
I check all but I dont see anything.... Step 1 and 2 are good....

I find something... I had a stereo link card on it... And at the step 3, when R44 doesn't work, I push the stereo switch, and now R44 is working BUT I cant see the -10 dB drop anymore, no more compression. To see the 10 dB drop, I have to push stereo switch again, compression is back BUT R44 doesn't work at thistime
I check + 10x everything but I can't find !

So I disconnect the stereo PCB. I plug the wire from the output pot to Ratio Bord pad 15 as a normal wiring, and calibration is OK ! R44 works perfecly but my 1176 has no stereo sidechain.
So the problem is from my Stereo link wiring ? stereo switch ? ... I cant see !!

Someone can help please ?

Here are some picture if you see something wrong, please tell me


_IGP5976 par volcanovap, sur Flickr


_IGP5977 par volcanovap, sur Flickr


_IGP5981 par volcanovap, sur Flickr


_IGP5978 par volcanovap, sur Flickr


_IGP5983 par volcanovap, sur Flickr


_IGP5982 par volcanovap, sur Flickr

My Rev A is working !!
just think to calibrate it with the switch in Mono position !
Thanks for your help

 

[late]

Anyone have used bourns model 95 pots for output? Have build one stereo rev d and one mono rev a. Every unit have same problem. When i turn output it gives a little bit noise. But if i take touch from case then it is gone.
 

http://fi.mouser.com/Search/ProductDetail.aspx?R=95A1D-Z28-EA0/301Lvirtualkey65210000virtualkey652-95A1DZ28EA0301L

 

[usekgb]

I used the Bourns in mine.  Really nice pot!  The only weird thing is that they feel completely different than the rest of the pots.  If you are ok with this, use one!

Cheers,
Zach

 

[Moose]

Steve_H's issue involved some troubleshooting that may help some down the road in the "my compressor passes a nice signal, but doesn't compress" category.  Here's an overview of the troubleshooting, it goes through most of the GR control amp.

He was getting an AC signal from the output pot to pad 22 and the ratio switch was trimming it correctly depending on the selected ratio.  His four gain reduction control amp transistors were lining well with the DC voltage chart and his AC signal was strong at the anode of the control amp output rectifier diodes (CR2 and CR3) and the rectified (DC) voltage was present at the anodes.

All Normal.

I seem to have EXACTLY this problem. There doesn't seem to be a good pad on my ratio board at the end of R58 (this board is actually pretty light-duty and pulling R2 to test will kill it if it wasn't already dead), and it doesn't connect to R61.  Is there a layout of the ratio board somewhere so I can at least figure out a jumper method to test this?

 

[mnats]

Is there a layout of the ratio board somewhere so I can at least figure out a jumper method to test this?

If you're looking for the rotary switch ratio board the layout is on my site. If you need the push button one there's a document on Hairball's site.

 

[Moose]

Is there a layout of the ratio board somewhere so I can at least figure out a jumper method to test this?

If you're looking for the rotary switch ratio board the layout is on my site. If you need the push button one there's a document on Hairball's site.

Thanks, and thanks in general for the massive amounts of information on your site, by the way.

I am looking for the push button layout, but I can't find it on Hairball. I found the layout for the power/vu/gr switch block, but the document only contains a table for resistor values for the ratio board. No layout.