All things G1176 - the new "repost" thread.

[tomcat]

Try to move the cable from the torroid to the pcb. On the picture it runs underneath the output xformer and pcb....

 

[Chrome Heart]

Alright, so I'll disconnect pin 1 of the xlr input from the grounding point.  That's where all my grounds go to.  Center tap and Power main.

I would also suggest to take gswans advice regarding test and calibration. If you dont follow those procedures before running audio through the unit, you will have no idea what you have. It would almost certainly be a disappointment.

 

[abecedarian]

Hi, I finished my G1176, 6 1/2 years ago when I started this thread back in 2004.  Back then, I think heat transfer fried something when the sun's rays, one hot summer day, baked the enclosure on the way to a studio in the back of my car. Stupid me : I know. It passes clean audio but very quietly and compression works. When in bypass mode, it's louder by a few dBs but really not much.  When the meter switch is placed at GR, the needle points to the red at around 3. Where do I start checking for problems?  Thanks for the help.  Glad to see this thread is still alive and well. 

If this helps: I'm using a T.C. Electronic M3000 in bypass as a mic pre. The input is cranked at +4dBu, the level of input is cranked up to +16db. The output is at +4dBu , output level cranked at +6db.  The G1176 input and outputs are at 12 o'clock. I'm monitoring it's signal output through logic pro using an apogee duo as an A/D, input set to XLR +4dBu. I have the main monitoring volume cranked all the way up to 0db.

 

[ward]

Where do I start checking for problems?

This thread is invaluable when looking for errors :
http://www.groupdiy.com/index.php?topic=4481

 

[kepeb]

hey,
i am stuffing 2x rev j pcbs, i have 32 1 questions today
1.
-
2.
can i use a 23v - 0 - 23v toroidal i have in my spares box?
3.
-

 

[gyraf]

Impossible to say (marked voltage may vary considerably) - try it and see...

Jakob E.

 

[alexilaiho]

is it possible please to use a vtb9045 wired 1k2:300 for the input ? thank you very much.

 

[domus]

Hi!
Thanks for all the great info here
Never build anything like this, but see this as a great learning project.Im currently working on building a g1176 using Mnats Rev J board with the Hairball T-attenuator, Altran 3837-1 and B11148.
I've been using this schematic: http://mnats.net/files/1176REVFG_SCHEMATIC.pdf

Thing is, I dont get the qbias to do anything when Im trying to calibrate. Measuring point 18 reads between 0 and -2,5V when turning full ccw and full cw.

Also I only get -7,5V at the -10V measuring point.
DC circuit zener diode CR6 is checked and ok.
VR1 gives away a perfect 30V.
Any suggestions on where to start looking..

thanks

 

[domus]

Anyone...

 

[lsskmki]

Hmmm, make sure your multimeter has a fresh battery. Check also that your power transformer gives enough volts. It's also good to triplecheck that the power transformer is wired correctly.
Can't help more than this.  Good luck.

 

[domus]

Thanks, gonna start with that
Gonna check everything again, hopefully I come up with something...

I´ll be back...hehe

 

[superslaukey]

using Mnats Rev J board

I've been using this schematic: http://mnats.net/files/1176REVFG_SCHEMATIC.pdf

Hey domus

why do you use a Rev J board and Ref F/G-Schematic? Maybe mixiung up Revs is the fault?

Best regards
Max

 

[nashkato]

hi
i'm in the progress of calibrating a G1176 .
i managed to get it up and running with the search , unfortunately i've yet another calibration question.

i must have wired something  wrong ,because while performing the GR tracking procedure , i realised i got less output on the 1:4 seeting than on the 1:20. ???
that's not right , is it ?
also the release pot got an influence on the gain reduction of about 1dB.
i've triple checked , i guess i'm not seeing the forest .

also , is it usual that when chaning the setting of ratio , the signal decreases and gets louder after half a second ?

any clue ?

 

[kepeb]

well i got rev j's and and have been using a BOM for G,H

from my understanding these were all compatible and variations of gyraf orignial?
the revisions a-d are the only ones that reflected different commercial layouts.

if this is not the case i guess i need clarification too.

EDIT: to clarify for domus superslaukey and myself.
I was following the suggested BOM download from mnats rev j page.

although it would appear on closer inspection that the link following this text:
Lab member fucanay has kindly reformatted my crappy html table BOM and converted it to a PDF file.
is not up to rev J.
i have yet to go over it and check for differences.

EDIT:
matched up on both BOM and Board for these listed revisions (between g/h and J) g1176 all appear the same
although the third and eighteenth caps could be combined (c3,c4 and c32 all 220pf ceramic) on the BOM.

 

[domus]

Power transformer working ok. Working with an oscilloscope so the batteries is not a problem

Well, looking at the schematics it seemed pretty straight forward to add in the Hairball kit with Altran, Bournes, T-attenuator and pushbuttons.
Bought the mnats Rev J when he still didn´t have the collaboration with Hairball as he does today...

Checked the BOM´s and they are the same. (mnats and fucanay)

Remembered that I couldn´t get hold of the Zener Diode 1N4740A, but used BZX85C10 instead. Can this cause the problem I have with getting -10V? (getting -7,5V right now)

 

[domus]

Ok, so I reaalllly checked the schematics, and the F/G schematic have different resistor values in the Signal Line Amp, also the semi-conductors are different. Assumed it was the same as for mnats Rev J pcb.

Still I don´t understand why I can´t get the -10V and also - shouldn´t turning qbias give some reading on the VU meter?

Can someone tell me the Q10 voltages?
I now have 13V on both G and S, shouldn´t turning qbias affect this?

sorry for the noob questions

thanks
 

 

[skal1]

hi lads ,


just a quick ?   i am about to calibrate my  rev j  mnats 1176 , i only have a digital meter to measure my 1khz 0dbu signal .

what digit should i see on my meter at 0db{0.775} or some thing different , also does the 1dbu drop equate  to {0.086}which is  needed to put the fet just into conduction

thanks


skal1
;D

hopefully this will help other , dug deep for this..

If it asks for 1 kHz at 0 dB, does this mean a 1 volt peak to peak on my scope hooked up to the signal generator? And +1 dB = ? volts p-p?

Okay, in this case, 0db = .775Vrms. That is your reference voltage.

.775 X 1.414 X 2 = peak to peak volts on the scope.

To find what voltage corresponds to +1db, use the formula:

db = 20[log(V1/V2)]

I'd just start plugging in values for V1, using .775V for V2, until you get the correct db result (+1). Or you could rearrange the above equation to solve exclusively for V1. :roll:

Don't forget to convert to P-P if you're using the scope to measure levels.

The Sifam VU or equivalent reads 1.23Vrms at 0db rather than .775Vrms because it is referenced to +4db, which is what you'll get if you plug 1.23V and .775V into the above equation.

To recap, .775Vrms is the 0db reference for all calibration procedures on the 1176.

Dean

Is this correct...


skal1

 

[SaMpLeGoD]

Hello all!
Well, I build some 1176LN Rev D, Rev A, Rev F and Rev J and all of them has the same minor problem: The VU's needle never stays quiet in GR mode with no signal, it always slightly swing around the "0" VU... Rev A is better than the others in this case... I experienced one original 1176LN black faces (REV D) and the needle is solid as rock pointing to the "0". even when I switch between +4 and GR the needle goes back to the "0" quick and firm...
I read, read, read here in the forum, and some people say that the original do the same thing, others are talking about a eventual dirt around the FETs... well, I clean the FETs, saw the original by myself and stand the opinion that, somehow, it must have any other reason to this happens!! circuit? VU? component's placement?
I tried with Hairballs big and small VUs, tried with SIFAMs AL29WF and AL19WF... all the comps act the same!
I have the FETs perfectly matched, Q12 and Q13 matched.... used 2N5088 with HFEs between 500 to 600 (greater that the 250 asked), all done, and regulated as it should! the comps sounds and acts perfectly, but that issue annoys me a lot...
any help or ideas???

Cheers,

Eddie.

 

[g fin]

Hi all! Here is my first post on this forum!
And here is my first DIY project, not working as good as I'd have expected...

First of all, I want to thank and congratulate Jakob for this project. It's such a pleasure to built this unit!

Now, I think I need your help.
I built a 1176 Gyraf, I got all voltages present in the schematic right.
I 've got signal, compression and good metering, but... Signal seems quite weak everywhere: I need to turn Input pot at ~12 o'clock to reach threshold, and when my output pot is fully clockwised I got the output signal slightly lower than the Input. Another strange thing: I've a kind of general low pass filter at the output. I would say that it sounds like an "Impedance problem"... I first thought to NE5532, changed it, and it's still the same... I checked all cap values, and they're good.

I've got another Idea, I used to have hum, and read somewhere this could be due to PCB resistance (copper to thin), so I soldered thin metal wire over the ground (on the PCB) and it worked! Could my current problem (sounding like impedance problem) be due to thickness of copper on the PCB?
If yes: do I have to tin all the PCB?

If not: Where should I search? what should I measure?

Thanks to all for your answers.

 

[skal1]

Hi lads/gals


I have built a mnats 1176 j rev  and  have been using it for a bout a year now , the only issue i have , is the frequency response curve i use  a oep tx , i did the 2k4 resistor change on the output it help the frequency response a bit .

i was a bit curious so i took out the tx and took another sample at the output capcitor at the junction primary of the tx  and it had the same frequency response curve as the tx out but with a lower level .


what is the frequency response of the signal amp , what would cause this lp roll of with no tx in circuit.


skla1