All things G1176 - the new "repost" thread.

[Babas]

Hi!

Quick question, am I supposed to see a drop in the incoming AC voltage at the minus side of C9 (Point 15)
when engaging GR mode (going from Bypass to GR)? The level of the drop corresponds to the different ratio settings, meaning
4:1 gives me a bigger drop than 20:1...

Regards,
Babs

 

[late]

I just finished my build and it sounds good. But when i record kick drum through it then i get phase problem. I have two kick tracks. I compress Kick1 and listen it with Kick2 (no compressed) i get phase problem. Flipping Kick1 phase helps or compressing Kick2 too.  I have rev A and not have same problem with it.

 

[creal]

I just finished my build and it sounds good. But when i record kick drum through it then i get phase problem. I have two kick tracks. I compress Kick1 and listen it with Kick2 (no compressed) i get phase problem. Flipping Kick1 phase helps or compressing Kick2 too.  I have rev A and not have same problem with it.

Are you sure, your wiring is correct?

 

[late]

I just finished my build and it sounds good. But when i record kick drum through it then i get phase problem. I have two kick tracks. I compress Kick1 and listen it with Kick2 (no compressed) i get phase problem. Flipping Kick1 phase helps or compressing Kick2 too.  I have rev A and not have same problem with it.

Are you sure, your wiring is correct?

Yes i think. Where is the possible mistake which reverse phase?

 

[late]

Now it work!! Output wiring mistake. Molex header hid marks, so i looked that it is same like input (- 0 +). But it is (+ 0 -) 

 

[audiophreak]

Hi Guys,
            Looking for a little Love here, can anyone comment on my connections and readings, or possible suggest an area for me to look into ?    I almost wish for a hard failure, that way It'd be obvious where to look ... 

    In the mean time , I've replace the " Slam " switch with a regular Lorlin and removed the Hairball push button  Meter switches with the mnats rotary with a Lorlin on one channel ,  to eliminate those Items as a cause and I get the same results ... good that I have eliminated these possibilities ,  bad that I still haven't found the problem/problems yet. 

  As stated, it passes clean audio, sounds like its compressing and things seem to change with attack and release and ratio adjustments, but in calibrating , when I get to  "6. Turn the attack control ON (CW)"" Engage Compression ""  and observe the drop in the meter reading."  I don't get a Drop in the Meter   

Thank you in advance for any and all help / suggestions

  Thanks ,
                Chip

EDIT - also ... when I do pass audio through the unit , both channels , the Meters react as you think they would in  +4 , GR and GR Bypass - just not accurately  I guess 

Hello All ,
          I have been putting this off for as long as I could ... I have searched and searched, read , tested , checked and rechecked to no avail ..  :'(

  I am trying to put together a Dual mnats  Rev.J's .  I have used the switch recommended on mnats page for the " Slam " mode for ratio with mnats ratio PCBs and Hairball push button Meter switches and PCBs.  I have connected "22" to the "22" pad on the Meter PCBs and "4" from the Ratio PCB to the "GRN" on the Meter PCB ( as thats one of the poles from the Ratio PCB ) and ran a Jumper from "28"( which is Ground) Pad on the Meter PCB to the "BLK" Pad on the Meter PCB  to short "22" to " Ground" for "GR Bypass"  ...  am I correct so far ?

    I have checked all the voltages listed here -

http://www.axtsystems.com/index.php?option=com_content&view=article&id=57:1176lnproblems&catid=34:1176ln&Itemid=62

.. and all voltages are close to spot on - only ( B of Q12 is +4.504vdc - was listed as +4.47vdc )  on one PCB  and ( E of Q9 is +13.58vdc - its listed as +13.1vdc  ) on the other  ... are these readings too far off ?

all other voltages are almost spot on -

PCB #1  TL071        PCB #2 TL071
pin 1 = -9.91            pin 1 = -9.91
pin 2 = -0.813          pin 2 = -0.825
pin 3 = -0.813          pin 3 = -o.825
pin 4 = -10.06          pin 4 = -10.05
pin 5 = -9.91            pin 5 = -9.91
pin 6 = 1.573          pin 6 = 1.572
pin 7 = 16.55          pin 7 = 16.70
pin 8 = 0.00            pin 8 = 0.00

    PCB #1
  - Q1  -  G= -1.519    S = 0.00    D = 0.00
  - Q10  - G=  -1.343  S =  -0.812  D = 16.56

  PCB #2
  - Q1  -  G= -1.436    S = 0.00    D = 0.00
  - Q10  - G=  -1.290  S =  -0.829  D = 16.7


  I have been able to set the " Q Bias "  properly ( or so i think )  when I get to the Gain Reduction Meter Tracking , I am able to  "2. With no signal applied, adjust VR55 so that the meter reads 0VU."
... and also -" 3. Apply a 0.245Vrms (-10dB) 1kHz sine wave signal to the input.
4. Switch the meter mode to +4dB.
5. Turn the output level control CW until the meter reads 0VU." 

.. but when I get to - "6. Turn the attack control ON (CW) and observe the drop in the meter reading."  I dont get a Drop in the Meter ????  no mater what i do  - I have then turned the " Input down " to see a -10dB on the Meter , then when I put it back in to " GR Bypass"  the Meter doesn't
move off of -10dB and when I max the " Output " pot all the way up the meter only climbs to about -5dB or so - ( eventhought I know its not right )  the Same in Both PCBs  ... and thats as far as I have gotten  :-[


  Both channels pass good clean audio, I can hear compression happening  , I am using a signal gen 1k at 0dB and -10dB for the calibrations verified with DMM.


  From reading I think my problem is in the GR Meter Driver Amp ?    but where to Start ?

    Thank you in advance for any and all help / suggestions

  Thanks ,
                Chip

 

[Spendor]

Thanks GSWAN for your reply to my previous post. I have both units up and running sweetly thanks.
I have been gifted 4 transformers which I would like to use in a new build. They are physically about 6X the size of the OEP's and are line matching TX's. The primary has 2 @ 150 Ohm windings. The secondary is a centre tapped 600 Ohm winding. I was told "With a low impedance source and high impedance load it is 20 Hz to 20kHz +- 0.5db peaking to +2dB at 40kHz", Sounds good to me! Could I use these on either the front end or the output of an 1176? If so would I need to modify anything (output resistor for example).
Thanks for advice!

 

[pintsized]

Hi all, I was hoping someone might be able to help me (a newbie) find a problem with my first build.

I used Mnats Rev J boards, with no input transformer, in a hairball case with hairball switches etc. I started stuffing the PCB without seeing the (wise) advice on only doing the power supply components first.. which was a shame! I've basically finished the entire build, but I'm not getting the correct readings on the power rails.

I'm seeing +30v as expected, but only -.04v on R85. I'm seeing -14v on the other side of R85 and the back of R86. I'm trying my best to understand the schematic well enough to diagnose (but struggling, clearly).. I'm seeing continuity from the middle wire of my AC supply all the way to R85 -10v measurement point, including C24, C25, C26 etc. CR6-10 are all oriented correctly as far as I can make out, as are C24-26. I'm guessing the problem is I have a short, but despite my best efforts I just don't understand it well enough to make the final leap. That is, the continuity I see to R85 appears to make sense to my eyes, so I can only assume I'm testing/thinking about it the wrong way?

Any help on how I should diagnose a problem like this would be much appreciated.

Everything else seems to be working fine.. it passes audio with no noise, input and output pots work as expected, and the metering works as expected in +4/+8. In GR meter mode (bearing in mind I obviously haven't calibrated yet), the needle slams to the right. Which seems odd but, with almost 0 volts to the gain reduction circuit I guess that's to be expected?

I ordered spares for most of the components, so if it turns out I've friend any transistors by accident I can easily replace them. I guess I just need to get the power supply working and go from there.

Any help with this would be most appreciated.. I'm pretty stumped!

Thanks,

James.

 

[pintsized]

Ok, ignore that!

I drank some more coffee and thought about it some more.. surely CR6 is there to prevent what I'm seeing?! I shouldn't read 0hms across it in both directions. So I found another zener diode, verified it was working, swapped the part, and I now have -10v DC at R85.

Very happy. Lets just hope I haven't fried anything

James.

Hi all, I was hoping someone might be able to help me (a newbie) find a problem with my first build.

I used Mnats Rev J boards, with no input transformer, in a hairball case with hairball switches etc. I started stuffing the PCB without seeing the (wise) advice on only doing the power supply components first.. which was a shame! I've basically finished the entire build, but I'm not getting the correct readings on the power rails.

I'm seeing +30v as expected, but only -.04v on R85. I'm seeing -14v on the other side of R85 and the back of R86. I'm trying my best to understand the schematic well enough to diagnose (but struggling, clearly).. I'm seeing continuity from the middle wire of my AC supply all the way to R85 -10v measurement point, including C24, C25, C26 etc. CR6-10 are all oriented correctly as far as I can make out, as are C24-26. I'm guessing the problem is I have a short, but despite my best efforts I just don't understand it well enough to make the final leap. That is, the continuity I see to R85 appears to make sense to my eyes, so I can only assume I'm testing/thinking about it the wrong way?

Any help on how I should diagnose a problem like this would be much appreciated.

Everything else seems to be working fine.. it passes audio with no noise, input and output pots work as expected, and the metering works as expected in +4/+8. In GR meter mode (bearing in mind I obviously haven't calibrated yet), the needle slams to the right. Which seems odd but, with almost 0 volts to the gain reduction circuit I guess that's to be expected?

I ordered spares for most of the components, so if it turns out I've friend any transistors by accident I can easily replace them. I guess I just need to get the power supply working and go from there.

Any help with this would be most appreciated.. I'm pretty stumped!

Thanks,

James.

 

[pintsized]

Hi again.

So moving on from my (now resolved) power supply problem, things were initially looking ok. But I've got bad voltage readings at Q12-Q15.

Q2 0.51 - 1.03 - 1.75
Q3 1.13 - 1.74 - 11.90
Q4 11.44 - 12.03 - 29.50
Q5 4.30 - 4.70 - 27.80
Q6 28.30 - 27.80 - 14.20
Q7 29.00 - 28.30 - 14.20
Q8 13.60 - 14.20 - 29.50
Q9 13.50 - 12.90 - 0.00
Q12 7.40 - 7.70 - 24.80
Q13 24.30 - 24.80 - 29.50
Q14 4.00 - 4.60 - 6.50
Q15 5.90 - 6.50 - 29.50

i've double checked all resistor values in the GR control amp circuit. Perhaps of interest, I'm getting 7.71v on the back of C17, which should be ~4.55v right?

This led me to suspect the ratio board, but I've checked all of the resistors there too.

My audio path is still working fine, and I can get gain reduction at 20:1. When I chose any other ratio, the GR needle goes to -20 and I have signal attenuation, but (to my ears) independent of attack and release. It just sort of goes quiet and flat reduces the output from what I can tell.

So it would seem something is up with my ratio board or the wiring around there, but it all looks and measures well.

Any ideas of other tests I could try? Am I right in assuming that 7.71v on C17 means the problem is occurring before the GR control amp?

Any suggestions welcomed and appreciated.

Many thanks,

James.

 

[gswan]

Check the resistor values in the GR section again. Particularly R61, R61, R62 and R68. The ratio switch resistors have nothing to do with the bias conditions of the transistors in the GR amp so you don't need to worry about them.

 

[pintsized]

Check the resistor values in the GR section again. Particularly R61, R61, R62 and R68. The ratio switch resistors have nothing to do with the bias conditions of the transistors in the GR amp so you don't need to worry about them.

Hi, thanks for the reply.

I've just double checked all of these. Anything that didn't give me a sane measurement in the board (R60 and R61) I lifted one leg and verified that way.. everything else showed correct measurements in place - I presume that's a sensible enough test? Or should I be lifting all of them? (sorry, newbie question I'm sure).

I've received replacement transistors for Q12-Q15. Is it worth me trying to swap those out?

Any other ideas?

Cheers,

James.

 

[gswan]

The transistors in circuit look like they are operating correctly. They should all be BC547 and have hfe>250.
The most common cause of upset in the DC bias conditions is incorrect resistor values, so continue checking to see if anything shows up.

 

[pintsized]

The transistors in circuit look like they are operating correctly. They should all be BC547 and have hfe>250.
The most common cause of upset in the DC bias conditions is incorrect resistor values, so continue checking to see if anything shows up.

I've just finished triple checking the resistors now.. R62-R75 all measure correctly on the board, I lifted one leg of R60/R61/R82/R83 to measure and they're all fine too. I went slowly to double check I didn't have a decimal wrong.. I'm as sure as I can be that they're all ok. Which is annoying because I really hoped to find it!

I have BC107 transistors for Q2,Q3,Q4,Q5,Q12,Q13,Q14 and Q15. Perhaps I'm missing something here.. is says BC107 on the schematic, not BC547?

Perhaps I should be checking other resistors? Is there anything you suggest I test that might narrow things down? I really am sure that all of the resistors in the GR control amp are correct.

In an ideal world I'd be using this in a session on Friday.. it's looking ever more unlikely, but whilst there's still a chance I'm willing to try any suggestions.

Thanks again for your time..

James.

 

[gswan]

BC547 (B/C) is the newer version of the BC107. Can be interchanged with no effect. Ideally you would have checked hfe for each transistor in the GR amp and selected those with hfe>250.
I'm assuming you have the unit in GR off mode when performing these tests, with no input signal. The DC conditions of the GR amp are isolated from everything else (caps on the input and caps on the output). You do have C19 and C20 in the correct way around? I'm assuming your table of transistor voltages are E-B-C columns?

 

[gswan]

Can you measure the voltage at the junction of R71/R72/R73/R67 and also the junction of R63/R64/R65 and the junction of R70/R69/R62?

Are you able to tell me what values you measured for each of the 14 resistors in this circuit?

 

[pintsized]

BC547 (B/C) is the newer version of the BC107. Can be interchanged with no effect. Ideally you would have checked hfe for each transistor in the GR amp and selected those with hfe>250.
I'm assuming you have the unit in GR off mode when performing these tests, with no input signal. The DC conditions of the GR amp are isolated from everything else (caps on the input and caps on the output). You do have C19 and C20 in the correct way around? I'm assuming your table of transistor voltages are E-B-C columns?

Ah, I see. I have four spare BC107s, and I've just put each in my tester.. they were all between 220 and 224. Hmm. These are a different batch to the ones currently on the board though.. so that doesn't tell us much, except all I would have done the first time around is type BC107 into Mouser and selected an obvious match - that is, I hadn't read any mention of hfe ratings, so I wont have paid attention to that. Do you think this is likely the problem, or is this "ideal world" stuff?

Yes, to clarify GR is off (SPDT switch from hairball, shorting pad 22 to ground), and nothing plugged into the input. I've just double checked C19 and C20, and they're correct. I did a careful scan of all polarised caps the other day to see if I'd made a mistake but they look good.

Yep, my voltage table is in E-B-C columns, sorry I meant to include a header. Here's my original spreadsheet which I used to see how far I off I was: https://docs.google.com/a/riverratrecords.com/spreadsheet/ccc?key=0AjuPWIf6dn1edEFIMGdPRk9KWmtFbjVwV0VVUVVoN1E#gid=0

Can you measure the voltage at the junction of R71/R72/R73/R67 and also the junction of R63/R64/R65 and the junction of R70/R69/R62?

Are you able to tell me what values you measured for each of the 14 resistors in this circuit?

I'll do this now.. thanks!

James.

 

[pintsized]

Can you measure the voltage at the junction of R71/R72/R73/R67 and also the junction of R63/R64/R65 and the junction of R70/R69/R62?

Are you able to tell me what values you measured for each of the 14 resistors in this circuit?

Legend! I started doing these measurements and found a lack of continuity at between R63 and R65. In removing the solder at R65 the pad looked burned. Perhaps I got it too hot when soldering. I had to repair the pad, and replaced R65 for good measure. My voltages are now looking much better!

Sheet #2 shows the new values..

https://docs.google.com/spreadsheet/ccc?key=0AjuPWIf6dn1edEFIMGdPRk9KWmtFbjVwV0VVUVVoN1E

Thanks for your help and patience, I'm learning loads! I'll attempt to calibrate again now and see how things go..

Cheers,

James.

 

[Autophase]

Hi guys, having.built and loving my gssl I've decided to add fet to my arsenal.
I intend to build 2x stereo units of the 1176, I was Hoping anyone the UK, could give me an.idea of cost and best place to source parts in the UK (I got most of the stuff for the gssl from rapid last time)
I would also appreciate any advice from those who have made stereo units.
Thanks

 

[gswan]

Hi guys, having.built and loving my gssl I've decided to add fet to my arsenal.
I intend to build 2x stereo units of the 1176, I was Hoping anyone the UK, could give me an.idea of cost and best place to source parts in the UK (I got most of the stuff for the gssl from rapid last time)
I would also appreciate any advice from those who have made stereo units.
Thanks

If by 'stereo' units you mean to operate them together on a stereo signal (as opposed to two compressors in the same box) then you need to make sure you have the time and facilities to perform a lot of matching of components for the two boards. Otherwise the compression curves will not be the same for both channels.